a comparative analysis of the moose rumen microbiota and
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University of VermontScholarWorks @ UVM
Graduate College Dissertations and Theses Dissertations and Theses
2015
A Comparative Analysis Of The Moose RumenMicrobiota And The Pursuit Of ImprovingFibrolytic Systems.Suzanne Ishaq PellegriniUniversity of Vermont
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Recommended CitationPellegrini, Suzanne Ishaq, "A Comparative Analysis Of The Moose Rumen Microbiota And The Pursuit Of Improving FibrolyticSystems." (2015). Graduate College Dissertations and Theses. 365.https://scholarworks.uvm.edu/graddis/365
A COMPARATIVE ANALYSIS OF THE MOOSE RUMEN MICROBIOTA AND THE
PURSUIT OF IMPROVING FIBROLYTIC SYSTEMS.
A Dissertation Presented
by
Suzanne Ishaq Pellegrini
to
The Faculty of the Graduate College
of
The University of Vermont
In Partial Fulfillment of the Requirements
For the Degree of Doctor of Philosophy
Specializing in Animal, Nutrition and Food Science
May, 2015
Defense Date: March 19, 2015
Dissertation Examination Committee:
André-Denis G. Wright, Ph.D., Advisor
Indra N. Sarkar, Ph.D., MLIS, Chairperson
John W. Barlow, Ph.D., D.V.M.
Douglas I. Johnson, Ph.D.
Stephanie D. McKay, Ph.D.
Cynthia J. Forehand, Ph.D., Dean of the Graduate College
ABSTRACT
The goal of the work presented herein was to further our understanding of the
rumen microbiota and microbiome of wild moose, and to use that understanding to
improve other processes. The moose has adapted to eating a diet of woody browse,
which is very high in fiber, but low in digestibility due to the complexity of the plant
polysaccharides, and the presence of tannins, lignin, and other plant-secondary
compounds. Therefore, it was hypothesized that the moose would host novel
microorganisms that would be capable of a wide variety of enzymatic functions, such as
improved fiber breakdown, metabolism of digestibility-reducing or toxic plant
compounds, or production of functional metabolites, such as volatile fatty acids, biogenic
amines, etc.
The first aim, naturally, was to identify the microorganisms present in the rumen
of moose, in this case, the bacteria, archaea, and protozoa. This was done using a variety
of high-throughput techniques focusing on the SSU rRNA gene (see CHAPTERS 2-5).
The second aim was to culture bacteria from the rumen of the moose in order to study
their biochemical capabilities (see CHAPTERS 6-7). The final aim was to apply those
cultured bacterial isolates to improve other systems. Specifically, bacteria from the
rumen of the moose was introduced to young lambs in order to colonize the digestive
tract, speed the pace of rumen development, and improve dietary efficiency (see
CHAPTER 8).
ii
CITATIONS
Material from this dissertation has been published in the following form:
Ishaq, S.L. and Wright, A-D.G.. (2012). Insight into the bacterial gut microbiome of the
North American moose (Alces alces). BMC Microbiology, 12:212.
Ishaq, S.L. and Wright, A-D.G.. (2013). Terrestrial Vertebrate Animal Metagenomics,
Wild Ruminants. In: Nelson K. (Ed.) Encyclopedia of Metagenomics: Springer
Reference. Springer-Verlag Berlin Heidelberg.
Ishaq, S.L. and Wright, A-D.G.. (2013). Wild Ruminants. In: Rumen Microbiology –
Evolution to Revolution. AK Puniya, R Singh, DN Kamra (Eds). Springer Publishing.
Ishaq, S.L. and Wright, A-D.G.. (2014). High-throughput DNA sequencing of the
ruminal bacteria from moose (Alces alces) in Vermont, Alaska, and Norway. Microbial
Ecology, 68(2):185-195.
Ishaq, S.L. and Wright, A-D.G.. (2014). Design and validation of four new primers for
next-generation sequencing to target the 18S rRNA gene of gastrointestinal ciliate
protozoa. Applied and Environmental Microbiology, 80(17): ahead of print.
Material from this dissertation has been submitted for publication to the International
Journal of Systemic and Evolutionary Microbiology on December 22, 2014 in the
following form:
Ishaq, S.L., Reis, D., Lachance, H., and Wright, A-D.G.. (2015). Descriptions of
Streptococcus alcis sp. nov. and Streptococcus vermontensis, sp. nov., and proposal of
three new subspecies of Streptococcus gallolyticus isolated from the rumen of moose
(Alces alces) in Vermont.
Material from this dissertation has been submitted for publication to BMC Microbiology
on February 23, 2015 in the following form:
Ishaq, S.L., Reis, D., and Wright, A-D.G.. (2015). Fibrolytic bacteria isolated from the
rumen of North American moose (Alces alces).
iii
Material from this dissertation has been submitted for publication to Applied and
Environmental Microbiology on February 11, 2015 in the following form:
Ishaq, S.L., Sundset, M.A., Crouse, J., and Wright, A-D.G. 2015. High-throughput DNA
sequencing of the moose rumen from different geographical location reveals a core
ruminal methanogenic archaeal diversity and a differential ciliate protozoal diversity.
iv
ACKNOWLEDGEMENTS
First and foremost, I want to thank my advisor and mentor, Dr. André-Denis Wright,
without whom this doctoral project would not have happened. Thanks for supporting
me professionally and personally, and especially for endlessly correcting my poor
spelling, putting up with my dry sense of humor, and helping me to mature into a
professional. Thanks to my other committee members, Dr. John Barlow, Dr. Doug
Johnson, Dr. Stephanie McKay, and Dr. Neil Sarkar for their interest in my work, their
constructive criticism, helpful suggestions, and for reading every page of this tome.
The entire Animal Science Department has my gratitude for too many reasons to list
here, but I would like to thank Jane O’Neil and Helen Maciejewski for all of the
paperwork they’ve done and phone calls they’ve made on my behalf. I’d like to thank
the Wright lab members: the undergraduates who were eager to learn laboratory skills
and help with my project, Dr. Benoit St-Pierre and Rachel P. Smith, M.S. for their
assistance in technical problems and discussions on analysis, Laura Cersosimo for
being my sounding-block and partner in science, and Christina Kim for helping me
collect rumen samples from sheep we had to chase down in a field in the hot July sun
because literally no one else was available. I’d like to thank my collaborators and those
individuals who assisted me in sample collection, as moose parts are not as easy to
come by as one would think.
v
On a more personal note, I’d like to thank my family for their heroic attempts to
understand my work and their unfailing support for my nine grueling years of higher
education. I especially need to thank my parents, Jill and Tony Pellegrini, for instilling
in me a love of reading, organization, and learning, as those have motivated me and
proved to be essential while writing this. I’d like to thank my friends, especially Laura
Cersosimo, Rachel Smith, Amanda Ochoa, Aimee Benjamin, Mital Pandya, and Mike
Haselton, for giving me something to do outside of work, and for always being willing
to inevitably talk about work. I want to thank JP Ishaq for his support for so many
years, even when I didn’t make it easy, and for putting up with me smelling like a wide
variety of animals after work. I’d like to thank everyone who lent a proverbial shoulder
to cry on during this last year, and especially for using those shoulders to move all my
stuff multiple times up and down stairs. I want to thank Lee Warren for his support in
the last and most stressful year of my Ph.D., especially when the only thing to do was
to hand me chocolate and hope for the best, and for being a willing participant in my
adventures. Finally, I would like to thank the Windows 7 version of Word for its help
formatting this beast, and for not being the Windows 8 version of Word.
vi
TABLE OF CONTENTS
CITATIONS…………………………………………………………………………..…..ii
ACKNOWLEDGEMENTS…………………………………………...………………….iv
LIST OF FIGURES…………………………………………………………………….xiii
LIST OF TABLES…………………………………………………………..…………..xv
CHAPTER 1 COMPREHENSIVE LITERATURE REVIEW ................................ 1
1.1. Moose .................................................................................................................. 1
1.1.1 Ecology and anatomy ...................................................................................... 1
1.1.2 Diet and Nutrition ........................................................................................... 3
1.2. Microbial phylogeny and the small-subunit rRNA genes................................... 5
1.3. An overview of the rumen microbiome and its role in digestion ....................... 8
1.3.1 Bacteria ........................................................................................................... 8
1.3.2 Archaea and methanogenesis ........................................................................ 11
1.3.3 Protozoa ........................................................................................................ 14
1.3.4 Fungi ............................................................................................................. 16
1.3.5 Dietary components and volatile fatty acids ................................................. 17
1.4. Probiotics and manipulation of the rumen environment ................................... 22
1.5. Summary ........................................................................................................... 23
1.6. References ......................................................................................................... 24
1.7. Figures............................................................................................................... 42
CHAPTER 2 INSIGHT INTO THE BACTERIAL GUT MICROBIOME OF
THE NORTH AMERICAN MOOSE (ALCES ALCES). .................................................. 43
2.1. Abstract ............................................................................................................. 44
2.2. Background ....................................................................................................... 45
vii
2.3. Results ............................................................................................................... 47
2.3.1 Quantitative Real-Time PCR ........................................................................ 47
2.3.2 PhyloChip Array ........................................................................................... 47
2.3.3 UniFrac analysis............................................................................................ 50
2.4. Discussion ......................................................................................................... 51
2.5. Materials and Methods ...................................................................................... 58
2.5.1 Sample Collection ......................................................................................... 58
2.5.2 DNA extraction ............................................................................................. 59
2.5.3 Quantitative Real-Time PCR ........................................................................ 59
2.5.4 PhyloChip ..................................................................................................... 60
2.5.5 Analysis......................................................................................................... 60
2.6. Competing Interests .......................................................................................... 62
2.7. Authors’ Contributions ..................................................................................... 62
2.8. Acknowledgements ........................................................................................... 62
2.9. References ......................................................................................................... 63
2.10. Figures........................................................................................................... 67
2.11. Tables ............................................................................................................ 73
2.12. Supplemental Material .................................................................................. 75
CHAPTER 3 HIGH-THROUGHPUT DNA SEQUENCING OF THE
RUMINAL BACTERIA FROM MOOSE (ALCES ALCES) IN VERMONT, ALASKA,
AND NORWAY. 81
3.1. Abstract ............................................................................................................. 82
3.2. Background ....................................................................................................... 83
3.3. Methods............................................................................................................. 85
viii
3.3.1 Sample Collection ......................................................................................... 85
3.3.2 DNA extraction and quantification ............................................................... 87
3.3.3 Amplicon library preparation ........................................................................ 87
3.3.4 Sequencing analysis ...................................................................................... 89
3.4. Results ............................................................................................................... 91
3.4.1 Classification of taxa by sample location ..................................................... 91
3.4.2 Statistical analysis of OTUs and clustering .................................................. 93
3.5. Discussion ......................................................................................................... 96
3.5.1 Bacteroidetes:Firmicutes............................................................................... 96
3.5.2 Temperature, region, or life stage? ............................................................... 99
3.6. Conclusion ...................................................................................................... 100
3.7. Availability of Supporting Data ...................................................................... 100
3.8. Competing Interests ........................................................................................ 100
3.9. Authors’ Contributions ................................................................................... 101
3.10. Acknowledgments....................................................................................... 101
3.11. References ................................................................................................... 101
3.12. Figures......................................................................................................... 106
3.13. Tables .......................................................................................................... 109
CHAPTER 4 DESIGN AND VALIDATION OF FOUR NEW PRIMERS FOR
NEXT-GENERATION SEQUENCING TO TARGET THE 18S RRNA GENE OF
GASTROINTESTINAL CILIATE PROTOZOA. .......................................................... 111
4.1. Abstract ........................................................................................................... 112
4.2. Introduction ..................................................................................................... 113
4.3. Materials and Methods .................................................................................... 115
ix
4.3.1 Sample collection and DNA extraction ...................................................... 115
4.3.2 Primer design .............................................................................................. 115
4.3.3 PCR amplification ....................................................................................... 116
4.3.4 Sequence analysis ....................................................................................... 117
4.4. Results ............................................................................................................. 119
4.4.1 Primer set 1: P-SSU-316F + GIC758R ....................................................... 119
4.4.2 Primer set 2: GIC1080F + GIC1578R ........................................................ 121
4.4.3 Primer set 3: GIC1184F + GIC1578R ........................................................ 122
4.4.4 Comparison of the three primer sets ........................................................... 122
4.5. Discussion ....................................................................................................... 123
4.6. Acknowledgements ......................................................................................... 127
4.7. References ....................................................................................................... 127
4.8. Figures............................................................................................................. 132
4.9. Tables .............................................................................................................. 135
4.10. Supplemental Material ................................................................................ 137
CHAPTER 5 HIGH-THROUGHPUT DNA SEQUENCING OF THE MOOSE
RUMEN FROM DIFFERENT GEOGRAPHICAL LOCATION REVEALS A CORE
RUMINAL METHANOGENIC ARCHAEAL DIVERSITY AND A DIFFERENTIAL
CILIATE PROTOZOAL DIVERSITY. .......................................................................... 138
5.1. Abstract ........................................................................................................... 139
5.2. Introduction ..................................................................................................... 140
5.3. Methods........................................................................................................... 141
5.3.1 Sequence analysis ....................................................................................... 142
5.3.2 Real-time PCR ............................................................................................ 143
5.4. Results ............................................................................................................. 144
x
5.4.1 Methanogens ............................................................................................... 144
5.4.2 Protozoa ...................................................................................................... 145
5.5. Discussion ....................................................................................................... 147
5.6. Acknowledgements ......................................................................................... 151
5.7. References ....................................................................................................... 151
5.8. Figures............................................................................................................. 157
5.9. Tables .............................................................................................................. 160
CHAPTER 6 DESCRIPTION OF STREPTOCOCCUS ALCIS, SP. NOV., AND
STREPTOCOCCUS VERMONTENSIS, SP. NOV., AND PROPOSAL OF THREE
NEW SUBSPECIES OF STREPTOCOCCUS GALLOLYTICUS ISOLATED FROM
THE RUMEN OF MOOSE (ALCES ALCES) IN VERMONT....................................... 163
6.1. Summary ......................................................................................................... 164
6.2. Description of Streptococcus alcis sp. nov. .................................................... 175
6.3. Description of Streptococcus vermontensis sp. nov. ...................................... 176
6.4. Description of Streptococcus gallolyticus subsp. mannosilyticus subsp. nov. 177
6.5. Description of Streptococcus gallolyticus subsp. melibiosilyticus subsp. nov.
178
6.6. Description of Streptococcus gallolyticus subsp. ruminantium subsp. nov.... 179
6.7. Conflict of interest .......................................................................................... 179
6.8. Acknowledgements ......................................................................................... 180
6.9. References ....................................................................................................... 180
6.10. Figures............................................................................................................. 185
6.11. Tables .......................................................................................................... 190
6.12. Supplemental Material ................................................................................ 195
xi
CHAPTER 7 FIBROLYTIC BACTERIA ISOLATED FROM THE RUMEN OF
NORTH AMERICAN MOOSE (ALCES ALCES). ......................................................... 197
7.1. Abstract ........................................................................................................... 198
7.2. Introduction ..................................................................................................... 199
7.3. Methods........................................................................................................... 200
7.4. Results ............................................................................................................. 203
7.5. Discussion ....................................................................................................... 204
7.6. References ....................................................................................................... 206
7.7. Figures............................................................................................................. 210
7.8. Tables .............................................................................................................. 212
CHAPTER 8 THE EFFECTS OF ADMINISTERING A FIBROLYTIC
PROBIOTIC MADE FROM MOOSE RUMEN BACTERIA TO NEONATAL LAMBS
…………...…………………………………………………………………………….213
8.1. Abstract ........................................................................................................... 214
8.2. Introduction ..................................................................................................... 215
8.3. Methods........................................................................................................... 217
8.3.1 Probiotic ...................................................................................................... 218
8.3.2 Production ................................................................................................... 220
8.3.3 Rumen sampling ......................................................................................... 220
8.3.4 Sequencing and DNA data analysis ............................................................ 221
8.3.5 Real-time PCR ............................................................................................ 222
8.4. Results ............................................................................................................. 223
8.4.1 Probiotic ...................................................................................................... 223
8.4.2 Production ................................................................................................... 223
8.4.3 Sequencing .................................................................................................. 225
xii
8.4.4 Real-time PCR ............................................................................................ 228
8.5. Discussion ....................................................................................................... 228
8.6. Acknowledgements ......................................................................................... 230
8.7. References ....................................................................................................... 231
8.8. Figures............................................................................................................. 236
8.9. Tables .............................................................................................................. 244
8.10. Supplemental Material ................................................................................ 245
CHAPTER 9 CONCLUSION .............................................................................. 248
9.1. Summary ......................................................................................................... 248
9.2. The moose rumen: summarized findings and unanswered questions ............. 248
9.3. Fibrolytic probiotics in lambs: beneficial or bust? ......................................... 251
9.4. Molecular methodology .................................................................................. 255
9.4.1 Sequencing Platform ................................................................................... 255
9.4.2 Sequencing Target ...................................................................................... 258
9.4.3 Bioinformatics Programs and Analysis ...................................................... 260
9.5. References ....................................................................................................... 261
9.6. Figures............................................................................................................. 267
9.7. Tables .............................................................................................................. 268
CHAPTER 10 COMPREHENSIVE BIBLIOGRAPHY ....................................... 269
xiii
LIST OF FIGURES
Figure 1-1 Diagram comparing the immature ruminant to the mature ruminant. ............ 42
Figure 1-2 The frequency of variability in the bacterial 16S rRNA gene [203]. .............. 42
Figure 1-3 Variable regions of the ciliate protozoal 18S rRNA. ...................................... 42
Figure 2-1 The OTUs found common in all samples (rumen and colon). ........................ 67
Figure 2-2 Breakdown of unclassified families by phylum. ............................................. 68
Figure 2-3 A comparison of the OTUs exclusive to the rumen or the colon. ................... 69
Figure 2-4 Jackknife environment clustering in UniFrac, by sample. .............................. 70
Figure 2-5 Principal component analysis (PCA) scatterplot of the environments
using the weighted UniFrac algorithm. ............................................................................. 71
Figure 2-6 Distribution of PhyloChip OTU’s for all 14 samples. .................................... 72
Figure 3-1 A comparison of sequences per sample, using the Silva bacterial
reference taxonomy for classification. ............................................................................ 106
Figure 3-2 FastUnifrac clustering of all 17 samples. A) weighted, non-
normalized, and B) unweighted. ..................................................................................... 107
Figure 3-3 PCoA graphs colored by variable. ................................................................ 108
Figure 4-1 A map of the full-length protozoal 18S rRNA gene, including variable
(V1-V9) and rumen ciliate signature regions (SR1-SR4), and showing the
respective amplicons of the three primer sets used in the present study. ....................... 132
Figure 4-2 Taxonomy and proportion of unique pyrosequences using NCBI
(BLAST), by forward primers P-SSU-316F (Sylvester et al., 2004), GIC1080F
(present study), and GIC1184F (present study). ............................................................. 133
Figure 4-3 Distribution of sequence identity percentages to known sequences
based on BLAST by sequencing primer. ........................................................................ 134
Figure 5-1 PCoA of moose (A, C, and E) and protozoa (B, D, and F). .......................... 157
Figure 5-2 Moose rumen methanogen taxonomy of total sequences, per sample
from Alaska, Norway and Vermont ................................................................................ 158
xiv
Figure 5-3 Moose rumen protozoal taxonomy of total sequences, per sample from
Norway and Vermont. ..................................................................................................... 159
Figure 6-1 Neighbor-joining tree comparing isolates to type isolates to lactic acid
bacteria. ........................................................................................................................... 185
Figure 6-2 UPGMA trees comparing novel isolates using the housekeeping genes
gmk (A), dpr (B), parC (C), pta (D), pyrC (E), recN(F), and rpoD (G). ........................ 186
Figure 7-1 Phylogenetic comparison of 31 isolates which known sequences
(NCBI). ........................................................................................................................... 210
Figure 7-2 Growth at various temperatures (A) and pHs (B), as measured by
optical density at 600 nm. ............................................................................................... 211
Figure 8-1 Group weight (kg) means over time.............................................................. 236
Figure 8-2 Group pH means over time. .......................................................................... 237
Figure 8-3 Volatile fatty acid (VFA) and ethanol profile of groups
(E=experimental, C=control) for two time points on pasture. ........................................ 238
Figure 8-4 Acetate to propionate ratio, with SEM. ......................................................... 239
Figure 8-5 Principal component analysis of samples by sampling time: May=teal,
June=green, July=red, and October=dark blue. .............................................................. 239
Figure 8-6 Diversity at the phylum level for all sequencing time points........................ 240
Figure 8-7 Diversity at the family level for all sequencing time points. ........................ 241
Figure 8-8 Real-time PCR data for methanogens and protozoa. .................................... 242
Figure 8-9 Comparison of methanogen versus protozoal densities for all samples ....... 243
Figure 9-1 Mean rumen pH over time, with standard deviation bars. ............................ 267
xv
LIST OF TABLES
Table 2-1 Estimated densities (16S rRNA copy numbers per gram wet weight) of
bacteria in the rumen (R) of the moose in October, 2010, Vermont. ............................... 73
Table 2-2 Total number of taxa found in each sample, before screening for
analysis but after background noise was removed and including only OTUs with
> 0.92 positive fraction. .................................................................................................... 74
Table 2-3 Statistics for samples taken from moose shot in October 2010 in
Vermont during the moose hunting season. ...................................................................... 74
Table 3-1 Metadata of the 17 samples from Alaska (AK), Norway (NO), and
Vermont (VT). ................................................................................................................ 109
Table 3-2 Statistical measures using a subset of sequences per sample. ........................ 110
Table 3-3 The number of shared OTUs across different samples at a 3% genetic
distance generated using a shared OTU table in MOTHUR. .......................................... 110
Table 4-1 Gastrointestinal tract ciliate protozoal primer specifications. ........................ 135
Table 4-2 18S rRNA protozoal reference sequences used to determine genetic
distance cutoff. ................................................................................................................ 136
Table 4-3 Comparison of statistical parameters and results for three primer sets. ......... 137
Table 5-1 Statistical measures per sample for methanogens (met) and protozoa
(prot) in Alaska (AK), Norway (NO), and Vermont (VT). ............................................ 160
Table 5-2 The number of shared OTUs and unique sequences across different
samples in Alaska (AK), Norway (NO), and Vermont (VT). ......................................... 161
Table 5-3 Real-time PCR results for methanogenic archaea and ciliate protozoa in
Alaska (AK), Norway (NO), and Vermont (VT). ........................................................... 162
Table 6-1Ability of isolates to produce biogenic amines from selected amino
acids, produce lipase, metabolize citrate, produce a ropy or non-ropy
exopolysaccharide, and extracellular protein production. .............................................. 190
Table 6-2 Acid production and ability of isolates to produce an acid byproduct
from a variety of carbohydrates. ..................................................................................... 192
xvi
Table 6-3 G+C content of isolates and DNA-DNA hybridization to reference
strains Streptococcus gallolyticus gallolyticus (ATCC 700065) and S. gallolyticus
macedonicus (ATCC BAA-249)..................................................................................... 194
Table 7-1 Isolate GenBank ID, closest GenBank match with percent identity,
growth on minimal media or on high salinity, and ability to reduce nitrite.................... 212
Table 8-1 Diversity statistics per sample for each of the four sampling time points. .... 244
Table 9-1 A comparison of the Silva bacterial database vs the Ribosomal
Database Project (RDP) bacterial reference files in ability to classify 16S rRNA
gene bacterial sequences. ................................................................................................ 268
1
CHAPTER 1 COMPREHENSIVE LITERATURE REVIEW
1.1 Moose
1.1.1 Ecology and anatomy
Moose, Alces alces, also known as Eurasian Elk in Europe, are the largest browsing
ruminant of the Cervidae (deer) family. They are unique among ruminants, as they do
not form herds, but will live individually, with the exceptions being mating season and
the first 9 to 10 months of a calf’s life. At maturity they reach upwards of 1.5 to 2 meters
at the shoulder, live up to 25 years in the wild, and weigh an average of 360 kg (females)
to 450 kg (males). Several subspecies of moose are recognized, for which geographic
isolation and adaptation has caused differential characteristics, such as antler shape. For
example, moose in Alaska (A. alces gigas) and eastern Siberia (A. alces buturlini) tend to
be larger, with males reaching up to 600 kg, and moose in Scandinavia (A. alces alces)
have white legs instead of the typical brown.
However, investigations of mitochondrial DNA have revealed conflicting results as to the
genetic validity of some subspecies [1–3]. Moose originally migrated to the United
States from Asia across the Bering Strait approximately 14,000 to 11,000 years ago.
From there, they dispersed across North America and genetic subspecies were eventually
established: A. alces gigas in Alaska and the Canadian Yukon, A. a. andersoni in western
Canada and the great lakes region of the US, A. a. shirasi from the Rocky Mountains and
Colorado to Alberta, Canada, and A. a. americana from the great lakes region to the east
coast [2]. In a comparison of the four proposed subspecies in North America,
2
mitochondrial diversity was slightly higher for populations in the center and lower in the
peripheral populations along the eastern and western cost (excluding Alaska) [2, 3]. The
implication was of a large central population which only relatively recently (as recent as
the 1900s) dispersed to peripheral territories, thus the genetic diversity between
subspecies was not entirely due to geographic isolation [2, 3].
Moose were traditionally found in most boreal and subarctic areas of the northern
hemisphere, but deforestation and over-hunting has reduced their range and, in some
areas, their population [4]. They do not thrive in warmer climates, and adults will often
lose weight during an unusually hot summer, although only calf weight is adversely
affected by overly cold winters [5]. Moose prefer young hardwood forest, deciduous
mixed forest, and salt-rich wetland habitats in the summer. Like all ruminants, moose
have a specialized digestive system with a four chambered stomach: rumen, reticulum,
omasum, and abomasum (Figure 1). The rumen/reticulum fosters a complex consortia of
microorganisms (bacteria, archaea, protozoa, fungi, viruses), and the collection of these is
known as microbiota. It is these microbiota which ferment plant matter that the animal
cannot breakdown on its own [6]. The omasum resorbs water from digesta, and the
abomasum secretes pepsin and rennet, and thus functionally resembles the glandular or
“true stomach”.
Moose are characterized by having wide mouths and long, flexible tongues that have
relatively few taste buds, resulting in browse selection based largely on olfactory cues
[7]. Molars and pre-molars are sharper than in many other ruminants, indicating a
3
specialization towards crushing tougher materials rather than grinding thin grasses [7].
The salivary glands are relatively large for ruminants, increasing in size for the summer,
allowing for excess saliva (specifically serous or enzyme-containing saliva) to pass into
the digestive tract. The saliva of deer also contains tannin-binding proteins [8]. Tannins
are plant-based polyphenols which can bind to proteins in the diet and make them
inaccessible for digestion, thus tannin-binding proteins aid in increasing the digestibility
of the diet.
The rumen is relatively small compared to other browsing ruminants of comparable size,
with a large reticulum capable of filtering larger particles back into circulation for
continued fermentation, a small yet elongated omasum, and an abomasum with unusually
thick mucosa [7]. Openings between stomach chambers are unusually wide and can be
further widened [7]; with the additional saliva this allows faster passage of forage
through the system during summer when food is plentiful. Faster passage of forage
through the digestive system has been shown to reduce methane emissions in domestic
cattle [9].
1.1.2 Diet and Nutrition
Diet selection and a preference for certain plant species can be seen in moose in different
locations, but trends towards certain genera can be seen across all moose. Deciduous or
coniferous leaves, twigs and stems are most often consumed, although moose have been
known to strip bark from ash and maple species. New growth is especially sought out, as
foliage is higher in protein and minerals than grass, and the concentrations of toxic plant
4
secondary compounds is lower. In western North America, the moose diet is
overwhelmingly (75-91%) comprised of willow species (Salix spp.), but will also
incorporate alder, aspen, and birch [10, 11]. In eastern North America, maple, ash,
hemlock, pine, fir, and birch comprised the primary diet of moose [12, 13]. In
Scandinavian countries (i.e. Norway, Sweden, Finland), birch and pine tend to dominate
the diet, as well as blueberry species [13–17].
Dietary efficiency decreases from summer through autumn, especially with respect to
cellulose digestion [18, 19]. Caloric intake decreases from summer into winter as well,
not only from reduced forage quality and quantity, but also from decreased production of
volatile fatty acids in the rumen, especially propionate and butyrate [18, 19].
Interestingly, moose will voluntarily reduce feed intake in the winter regardless of quality
and quantity of feed supplied [20]. Moose commonly lose up to 20% of body weight
over winter [21], a cycle which is common to other arctic cervids, such as reindeer.
Moose, especially pregnant cows, show an increased preference for aquatic wetland plant
and algae species when they are available during the summer, and specifically for those
species with a high salt content, such as green algae, Spirogyra sp., and bladderworts,
Utricularis sp. [22]. An estimated 94-96% of sodium intake for a moose comes from
aquatic species eaten during the summer; not only can moose detect salt concentrations as
low as 1 mmol (or 100 milli-equivalent/liter), but they appear to have an effective method
of sodium retention which reduces excess excretion in urine and feces [22]. In addition
5
to salt, feeding on aquatic plants provides extra water in the diet which is required for
ruminant digestion and peristaltic movement.
1.1.2.1. Modified Diets
There has been some research done on formulated rations for captive moose with variable
success [23, 24]. Moose fed on large quantities of grass forages are prone to declining
health caused by chronic diarrhea and wasting, which can eventually lead to death [24].
Moose, like all ruminants, are also prone to lactic acidosis or “grain overload” [25]. This
is common when an animal switches from a natural cellulose-based diet to a
manufactured or otherwise highly-digestible starch-based diet. The sudden change in
food type causes a sudden shift in rumen bacterial communities, generally from gram-
negative to gram-positive bacteria, and promotes the faster replicating lactic-acid
bacterial species which prefer a starch substrate. Excess lactic acid is produced, lowering
ruminal pH below pH 5.5, which can kill naturally-occurring populations of
microorganisms, such as the rumen protozoa [25]. Not only does this decrease appetite
and feed intake, but larger amounts of ruminal acid are transported across the rumen wall
and into the bloodstream, leading to a more serious metabolic acidosis.
1.2 Microbial phylogeny and the small-subunit rRNA genes
Metagenomic studies do not usually employ culturing techniques, and many rumen
microorganisms are too recalcitrant to culture. Thus, putative identification is made
using pairwise gene sequence comparisons to known species. The small subunit of the
ribosome (SSU rRNA) provides a good platform for both current molecular methods, but
6
comparative phylogeny as well as, although the gene itself does not provide any
information about the phenotypic functionality of the organism. Overall, the rRNA genes
evolve very slowly and, since they are ubiquitous, they can be used for comparison across
wide variety of taxa.
Prokaryotes, such as bacteria and archaea, have a 16S rRNA gene which is approximately
1,600 base pairs in length. Eukaryotes, such as protozoa, fungi, plants, animals, etc.,
have an 18S rRNA gene which is up to 2,300 base pairs in length, depending on the
kingdom. In both cases, the S stands for Svedberg Units, or sedimentation rates of the
RNA molecule, and is a relative measure of weight and size. Thus, the 18S is larger than
the 16S. In both genes, there exist regions which are conserved (identical or near-
identical) across taxa, and nine variable regions (V1-V9) [26]. The variable regions are
not under functional constraint and are prone to higher evolutionary rates (Figures 2, 3),
providing a means for identification and classification through analysis [27–31]. The
conserved areas are targets for primers, as a single primer can bind universally (to all or
nearly-all) to its target taxa.
In addition to a small subunit, ribosomes also possess a large subunit (LSU rRNA), the
23S rRNA in prokaryotes, and the 28S rRNA in eukaryotes. Eukaryotes have an
additional 5.8S subunit which is non-coding, and all small and large units of RNA have
associated proteins which aid in structure and function. Taken together, this gives a
combined 70S ribosome in prokaryotes, and a combined 80S ribosome rRNA in
eukaryotes.
7
The two main challenges facing high-throughput sequencing are in choosing a target for
amplification, and being able to integrate the generated data into an increased
understanding of the microbiome of the environment being studied, both of which are
discussed further on pages 255-260. High-throughput sequencing can currently sequence
thousands to millions of reads which are up to 600 bases in length for amplicons and
1,000 bases in length for genomic DNA (e.g. Roche 454). This has forced studies to
choose which variable regions of the rRNA gene to amplify and sequence, and has
opened up an arena for debate on which variable region to choose [27].
Additionally, the ability to sequence microorganisms without culturing first has led to the
exponential growth of online sequence databases, which have variable amounts of
detailed information about the sequence entry. Indeed, many bacterial sequences in
GenBank are listed as “unclassified” or “uncultured”, making taxonomic analysis for
high-throughput methods difficult. Operational Taxonomic Units (OTUs) are a
bioinformatics tool for grouping sequences based on percent identity to known
sequences, and in this way sequences can have an assigned level of taxonomy even when
the taxonomic resolution is low due to short reads, or when sequences cannot be
putatively identified using public databases. Different metagenomic studies also assign
OTUs at different taxonomic level (97%, 98%, or 99% for bacteria), which can make
analysis across studies difficult.
8
In recent years, the advances in de novo shotgun sequencing has allowed for the large-
scale investigation of a variety of microbiomes [32, 33]. While microbiome refers to the
collective genetic material or genomes of all the microorganisms in a specific
environment, the term is often casually used interchangeably with “microbiota”, or is
used to describe only the genetic material of a specific type of microorganism (i.e.
“microbiome” instead of “bacterial microbiome”). While the same challenge of
sequencing without culturing still applies; in that you can identify which pieces of the
puzzle are present but not always how they fit together, shotgun sequencing allows for
the entire genome to be sequenced. DNA is enzymatically or physically cut into small
pieces which are sequenced, these pieces are assembled into contigs or short sections,
which themselves are then assembled to more or less recreate the entire genome. This
allows for the identification of putative genes for different enzymes, and detailed
comparisons of species across multiple loci instead of just one gene. Naturally, this
process comes with its own drawbacks of technical difficulties, extremely high data
output, and the logistical challenges of reassembling an entire genome. However, it is an
interesting way of identifying form and function in a single method, and is furthering the
field of molecular genetics.
1.3 An overview of the rumen microbiome and its role in digestion
1.3.1 Bacteria
The most important tool a scientist can possess is curiosity; however, the inventor of the
microscope and the “Father of Microbiology” was not a scientist by traditional terms.
Antonie van Leeuwenhoek was a draper, a local politician, and a lens-maker in the 1600s
9
to early 1700s, and it was using these home-made lenses that he began to observe things
on a cellular level. He was the first person to view and describe single-celled organisms,
such as bacteria, protozoa, and spermatozoa, which he referred to as “animalcules” or
“wee beasties”. To date, there are 30 valid bacterial phyla [34, 35], with several more
candidate phyla in use (i.e. OP1, TM7, etc.) [36]; however, only a selection of these are
found to colonize the rumen. Some phyla, such as those which contain aquatic or soil
bacteria (i.e. Chlorobi or Verrucomicrobia, respectively), are often found in the digestive
tract as a result of incidental ingestion, and are thought to be transient members of the
rumen. The two main phyla which tend to dominant the gastrointestinal tract (GIT) are
Bacteroidetes and Firmicutes.
Currently, the phylum Bacteroidetes contains over 7,000 species, genetically adapted to a
wide range of environments, such as soil, water, and the GIT [37]. Bacteria belong to the
phylum Bacteroidetes are gram-negative anaerobes or aerobes, and it is generally
anaerobic members that belong to the class Bacteroidia (formerly Bacteroides) that are
found in all parts of the GIT. As members of the phylum Bacteroidetes possess a wide
range of enzymes, especially those which digest carbohydrates or proteins, the species
profile for the host GIT is determined by the diet of the host. In the GIT, some of them
produce butyrate, which has been implicated in upregulating the GI immune system [38],
and can alter toxic or mutagenic compounds [39].
In healthy humans, Bacteroidetes is the dominant phyla [40–42]; however, in obese
humans Bacteroidetes bacteria are decreased and Firmicutes is the dominant phylum [43–
10
45]. This is in contrast to ruminants, which are more likely to have Firmicutes as the
dominant phylum [46–53]. However, several studies have identified Bacteroidetes as the
dominant phylum in adult ruminants [47, 54], growing ruminants [55], and ruminants
transitioning to a high-starch diet [56]. Firmicutes bacteria are gram-positive, often form
endospores, and are divided into two major classes: Clostridia and Bacilli. Bacteria
belonging to the class Clostridia are strict anaerobes, are also found in soil, and many are
characterized as cellulolytic, such as Butyrivibrio spp. [52], Clostridium spp. [57], or
Ruminococcus spp. [58]. Within the class Bacilli, the major rumen taxa of interest are
cellulolytic Bacillus species [59, 60] or lactic acid bacteria (order Lactobacilliales), such
as Lactobacillus spp., Lactococcus spp., Enterococcus spp., and Streptococcus spp. [61].
Other major phyla include Fibrobacteres, which contains cellulolytic bacteria, is common
to the GIT [62, 63], and is not well understood as a group as they are difficult to culture.
Bacteria belonging to the phylum Proteobacteria are more prevalent in the intestines or
colon [46, 64], and many are pathogenic, such as Helicobacter or Campylobacter.
However, some species of Proteobacteria have been found to be capable of breaking
down plant compounds, such as lignin [65]. Bacteria from the phylum Actinobacteria
can also be found in the GIT. Many Actinobacteria species are acetogenic, produce
antibiotics or other pharmacologically important compounds [66], or are used to create
dairy products, such as Bifidobacterium spp.
11
1.3.2 Archaea and methanogenesis
In 1990, a four page article revolutionized the way we classify microbes [67]. From
humble beginnings comes the story of archaea, which could not be correctly classified
using the Linnaean system of taxonomy, and not even the prokaryote-eukaryote division
could settle the issue. Though studies had already been done on these microorganisms
[68], they did not yet have a place on the tree of life. Thus, the Domain level of
classification was introduced [67], and the potential for microbial research on archaea
was suddenly limitless. The Archaeal domain is divided into two main phyla,
Euryarchaeota, representing methanogens and related species, and Crenarchaeota,
representing the thermophilic extremophiles, and three presumptive phyla: Korachaeota,
Nanoarchaeota, and Thaumarchaeota [69].
Despite providing a multitude of research opportunities, methanogens were quickly
singled out as a potential target for reducing the production of methane from various
agricultural and industrial sources. Methane has 25 times more potential for global
warming than carbon dioxide, 21 times more if you measure it as the combustion of
methane into carbon dioxide [70, 71]. As of 2012 in the US, enteric fermentation from
domestic livestock was the second largest source of human-related agricultural methane,
accounting for 141 Tg CO2 Eq/year (equivalent of a million metric tons of carbon
dioxide) [70]. Nitrous oxide has a potential of 298 times greater than carbon dioxide, and
agricultural soil management creates 204.6 Tg CO2 Eq emissions, while manure
management systems create 17.9 Tg CO2 Eq/year in the US [70]. Why then have we
focused on methane from enteric fermentations?
12
For domestic livestock, methanogenesis represents a loss of dietary efficiency as
compounds such as acetate or hydrogen are sequestered by methanogens instead of being
used by the host for production (i.e. live weight gain, milk production, wool production,
etc.). Much research has been done on methanogenesis and rumen microbial populations
between domestic and wild ruminants, as wild ruminants (bison, elk and deer) are
estimated to produce up to 0.37 Tg CO2 Eq/year [72, 73]. This is a drastically different
figure than that for domestic livestock, yet population differences are not the only factor.
There are, for example, an estimated 300,000 moose and 25 million white-tailed deer [74]
in the US, versus 90 million cattle registered with the USDA [75]. Thus, wild ruminants
are presumed to produce less methane based on a presumed higher dietary efficiency and
lower production demands.
Ammonia, hydrogen, and carbon dioxide gas are also produced by enteric fermentation,
and their partial pressure drives many reactions in the rumen [76]. Methane gas is
created when hydrogen, available as free protons, H2 gas or NADH and NADPH
cofactors, is used to reduce carbon dioxide. It is thermodynamically favorable, and it
prevents the accumulation of hydrogen gas in the digestive tract which can be harmful to
both microorganisms and host [76]. In addition to living freely in rumen fluid, attached
to particulate matter, or attached GIT epithelia [77], many methanogens can be found
attached to the extracellular surface or intracellularly within protozoa as symbiotic way of
capturing the hydrogen that the protozoa releases [78–80]. Methanogenic archaea
13
harness this process to generate energy, although some gamma- and alpha-proteobacteria
are methanotrophs, and are capable of using methane as their carbon source.
A few different one- or two-carbon molecules may also be used to provide the carbon
dioxide and hydrogen necessary for methanogenesis. Acetate, a volatile fatty acid (VFA)
released as a byproduct of enteric fermentation, can be used to form methane along
several different enzyme pathways. Interestingly, acetogenesis can also act as a hydrogen
sink and will inhibit methanogenesis, though it is in not thermodynamically favorable
under normal rumen conditions. The hydrogen threshold of a methanogen is up to 100
times lower than for than for the reductive acetogenesis pathway, thus a large
methanogen population will reduce the hydrogen concentration below the threshold of
acetogenesis and render it inactive [81, 82].
Formic acid can also be broken down to carbon dioxide and hydrogen, both of which can
be used to form methane, by the enzyme hydrogenlyase, known also as hydrogenase or
formate hydrogenlyase [68]. Hydrogenlyase can be found in other archaeal species like
Thermococcus, and has also been studied in the bacterium Escherichia coli, which uses
the enzyme formate hydrogenlyase (formate dehydrogenase coupled hydrogenase, FDH-
MHY) complex to generate electron acceptors under anaerobic conditions, if formate is
available [83]. Formate in the rumen is provided through consumption of fruit or honey,
dietary supplementation, or bacterial production. Various rumen bacteria, such as
Butyrivibrio, Clostridium, Fibrobacter, Lachnospira, Oxalobacter, Prevotella,
Ruminobacter, Ruminococcus, Streptococcus, or Succinovibrio [84] produce formate.
14
Methanol, a breakdown product of pectin, can also be used for methanogenesis.
Regardless of the carbon source and enzyme pathway used, the final step of
methanogenesis is catalyzed by the methyl-coenzyme M reductase (mcr) gene and is
present in all methanogens [85, 86].
The overwhelming majority of rumen methanogen diversity belongs to the genus
Methanobrevibacter (Mbr.) [87–92]. The two main species identified include Mbr.
smithii [91, 93, 94], which been shown to improve polysaccharide fermentation by
bacteria [95, 96], and Mbr. ruminantium [97], which is associated with a lower
calorie/high-forage diet [98]. Methanobrevibacter thaueri is typically low in ruminants,
but was found in reasonably high numbers in impala [99] and moose [100].
Methanosphaera stadtmanae strictly uses methanol for methanogenesis, and thus is more
prevalent in omnivorous or fruitivorous monogastrics [91, 101, 102], and ruminants with
higher pectin diets [99, 100].
1.3.3 Protozoa
After the initial discovery by Antonie van Leeuwenhoek in the 1600s, protozoa were
discovered nearly 200 years ago [103–105]. Rumen protozoa represent the largest
microbial biomass, although they are not the most abundant, and are important
contributors to plant biomass degradation [106–110]. Identification of protozoa in the
digestive tract has traditionally been accomplished via microscopic identification [79,
15
107, 111–117], or other molecular methods [118–121], although a few high-throughput
studies have recently been published [100, 122–126].
The rumen protozoa, all of which possess cilia as a means of transport, are divided into
two main orders: the Entodiniomorphida, some of which are cellulolytic and have one or
two zones or bands of cilia on the anterior end (i.e. Entodinium, Epidinium, etc.), and the
Vestibuliderida, which are completely covered in cilia, and thus, more motile (i.e.
Dasytricha, Isotricha). Common rumen protozoa include Entodinium spp., Epidinium
spp., Eudiplodinium spp., Isotricha spp., Ophryoscolex spp., and Polyplastron
multivesiculatum, [127].
Fibrolytic protozoal species include Polyplastron multivesiculatum [110], Eudiplodinium
spp. [128, 129], Enoploplastron spp. [114], and Diplodinium sp. [114], to name a few.
Entodinium spp. are a major source of starch and bacterial digestion in the rumen [130].
While total protozoal counts are higher in concentrate selectors [131], Entodinium
populations are decreased on a high-concentrate diet versus a roughage diet [131],
possible due to a shift in the bacteria populations which the Entodinium prey upon.
Protozoa are sensitive to changes in pH [132], and factors such as diet [87, 131, 133] and
weaning strategy [134] will have an effect on the diversity and quantity of rumen
protozoa. Likewise, changes in the protozoal population can alter the density of rumen
methanogens which use protozoa as a source for hydrogen in methanogenesis.
Polyplastron, Eudiplodinium, and Entodinium species have been shown to closely
16
associate with some methanogens, such as Methanosphaera stadtmanae and Mbr.
ruminantium [135–137].
1.3.4 Fungi
Despite contributing to the breakdown of plant material in the rumen [138–141],
relatively little work has been done on identifying rumen fungi or understanding their
interactions with other rumen microorganisms. Rumen fungi exist in a plant-associated
vegetative state or a free-living zoospore state, which was previously thought to be
protozoa [138]. Prior to work by C.G. Orpin in the mid-1970s [142, 143], fungi had not
been confirmed to colonize in anaerobic environments.
Currently, all identified anaerobic fungi are classified within the order Neocallimastigales
(phylum Neocallimastigomycota) [144]. Genera commonly found in the rumen include
Anaeromyces, Caecomyces, Cyllamyces, Neocallimastix, Orpinomyces, Piromyces, and
Trichoderma, all of which are fibrolytic [139, 145]. To date, fungi have been identified
in a variety of African ruminants [146], domestic ruminants [140, 146, 147], and
herbivorous reptiles [146, 148]. Fungi have also been investigated for use as a probiotic
for ruminants [149].
In vitro, co-culturing rumen fungi and the archaeal Methanobrevibacter smithii increased
xylanase activity and promoted acetate formation over lactate [96]. Likewise, some
strains of lactate-utilizing bacteria stimulated the cellulolytic capabilities of fungi in co-
culture [150], while cellulolytic bacteria inhibited it [151].
17
Typically, fungi are identified using the internal transcribed spacer (ITS) region of non-
functional DNA between regions coding for ribosomal subunits. Other potential targets
for identification, such as the rRNA genes, nuclear housekeeping genes, or mitochondrial
genes, are complicated by poor-quality PCR amplification or sequencing, products which
are too large for most current next-generation sequencing techniques, or by low gene
variability leading to insufficient resolution for identification [152]. In the case of the
phylum Neocallimastigomycota, which encompasses many genera of rumen fungi,
mitochondria are entirely lacking.
1.3.5 Dietary components and volatile fatty acids
Dietary fiber is the naturally occurring component of plants which is indigestible to
animals that lack the proper digestive enzymes. Fiber is a general term which
encompasses pectin, gums, mucilage, cellulose, hemicellulose, and lignin. Both pectin
and gums are water-soluble, but those fibers that are found in plant cells walls, such as
cellulose, hemicellulose, and lignin, are water-insoluble. Dietary fiber not only provides
bulk to the diet and aids in water-retention in the intestines, but in the case of ruminants,
plant fibers act as substrates to the fibrolytic microorganisms in the GIT, and a certain
percentage of fiber is required in the diet to maintain a healthy, functioning rumen.
Fibrolytic microorganisms use various polysaccharide-digesting enzymes, like cellulases,
hemicellulase, glucosidehydrolases, xylanase, etc., to break down plant biomass.
Cellulose is a linear polysaccharide of 15-10,000 glucose molecules connected by β-1,4
18
glycosidic linkages, and provides the structural support in cell walls, which allows for
plant growth. Thus, is in the most abundant organic polymer on Earth. As the plant
matures and grows in size, the structural components and cellulose content of the plant
are increased, leading to a decrease in the digestibility of the plant and lowering its
nutritional content. Cellulose can exist as a crystalline structure, as in cotton fibers, or as
a manufactured derivative, such as carboxymethylcellulose, which is more water-soluble.
Acidic treatment or very high temperatures can make cellulose amorphous and soluble in
water.
The crystalline structure can vary depending on the organism which created it. For
example, plants create cellulose 1β, which is often mixed with hemicelluloses and lignin
to decrease hydrophobia, while bacteria and algae create cellulose 1α, which is found in
longer strands and has a higher tensile strength. The cellulase enzyme, often also known
as β-1,4 endoglucanase, is actually a group of enzymes. Due to the differing structure of
cellulose, all endoglucanase enzymes breakdown cellulose using slightly different
actions. In the rumen, bacteria, protozoa, and fungi all produces cellulases [58–60, 106,
110, 139, 145, 153].
Hemicelluloses, also called arabinoxylans, are polysaccharides that make up the plant
wall, but are less complex (500-3,000 glucose units) than cellulose, and are found in a
branched, amorphous structure. Hemicelluloses include xylan, arabinoxylan,
glucuronoxylan, glucomannan, and xyloglucan, and as a group are much more abundant
19
than cellulose. Hemicellulase enzymes are, likewise, as varied as their substrates and are
also produced by rumen bacteria, protozoa and fungi [141, 145, 154–156].
Starch is another plant polysaccharide comprised of glucose units; however, it is more
easily digested as both microorganisms and animals possess the required enzymes.
Glucose units bound together with α-1,4 glycosidic bonds form the helical sugar amylose,
which is more resistant to digestion due to its shape. Amylopectin, which is also a
polymer of glucose units with α-1,4 glycosidic bonds, has branching which occurs at the
evenly spaced α-1,4 glycosidic bonds. Amylose and amylopectin are the two
components of starches, and while amylopectin will make up at least 70% of the starch,
there will be different proportions of each depending on the type of starch. Amylose, an
enzyme commonly found in saliva and intestines, is able to hydrolyze amylopectin. New
growth plants tend to have higher concentrations of starch, which declines as the season
progresses and the energy from stored starch is used to facilitate plant growth.
Lignin is an important component of plant cell walls, as it is covalently bonded to
hemicellulose, and fills the space in cell walls to provide flexibility and mechanical
strength to the plant. Lignin is hydrophobic, allows for water transport through the plants
vascular system without allowing it to move osmotically across every cell wall.
Although it provides a great deal of carbon, it is of no nutritional value to the ruminant.
Rumen bacteria and fungi, some of which are able to breakdown lignin, are able to
increase the dietary efficiency of the host and the digestibility of the forage [65, 141, 149,
157].
20
The products of these plant polysaccharide-targeting enzymes are smaller molecules of
cellobiose (glucose dimers) or glucose monomers, which are then fermented by the gut
microorganisms. As any free glucose in the rumen is immediately fermented by
microorganisms, the host relies on other products for energy. These microbial by-
products are primarily short-chain or volatile fatty acids (VFAs) like propionic, acetic,
and butyric acids, and to a lesser extent, isobutyrate, valerate, isovalerate, 2-
methylbutyric, hexanoic, and heptanoic acids, which are absorbed across the rumen wall
and can be used as energy by the host [158–160]. For the most part, these VFAs can be
interconverted, and will work towards equilibrium even as new VFAs are introduced into
the rumen.
Fiber digestion in the rumen increases the production of the VFA acetate, which is the
major VFA found in the rumen and accounts for the increasing proportion of acetate
production in the rumen on a higher-forage winter diet [6, 18, 19, 161]. Acetic acid is
used for adenosine triphosphate (ATP) synthesis, body fat synthesis, milk synthesis,
producing acetyl-CoA for lipogenesis, increasing blood flow to the colon, and other
associated health benefits [162].
Sugar, starch, and pectin digestion in the rumen favors the pathway to create the VFA
propionate, which accounts for the higher concentrations of propionate production in
summer as compared to autumn/winter [6, 18, 19]. Propionate is a biologically important
metabolite that is used for gluconeogenesis in the liver, for energy in milk synthesis, it
21
can induce satiety, and has a variety of other health benefits [163, 164]. The production
of propionate reduces the amount of free hydrogen in the rumen, and combined with a
drop in the methanogen-commensal protozoal populations associated with high starch
diets, this leads to a decrease in methanogenesis and total methanogen populations [133,
165]. Thus, a lower acetate to propionate ratio is indicative of increased dietary
efficiency.
Butyrate is an important VFA as it provides energy for the rumen wall itself, as well as
intestinal epithelia. It is also used in fat or milk synthesis, and has been shown to reduce
inflammation and carcinogenesis in the colon [38, 162, 166, 167]. Butyrate production is
increased with a higher fiber diet, and decreased with diets higher in gums [167].
Lactic acid, or lactate, can be used in lieu of glucose as a carbon source by lactose-
fermenting bacteria and yeast [168, 169], and is an intermediate step in the production of
other VFAs, such as propionate [168]. However, when a rapidly-fermentable
carbohydrate, such as some types of starch, is ingested by the ruminant in large
quantities, it can lead to a rapid accumulation of lactic acid, which reduces the pH to a
point where microorganisms are killed and normal rumen fermentation processes are
inhibited [170–173]. Fibrolytic bacteria and protozoa require an environmental pH of
6.3 to 7.0, amylolytic bacteria prefer pH 5.5 to 6.5, and fungi require 6.0 to 7.0.
22
1.4 Probiotics and manipulation of the rumen environment
Probiotics are live microbial cultures which are administered to promote healthy
digestive function and normal microbiota. Probiotics are typically monocultures or
comprised of a few species of bacteria [174–179], although yeast [180], and even fungi
[149] have been used as probiotics in humans and animals. Transfaunation is the process
of transferring rumen contents from one host to another, in contrast to fecal transfer,
which uses material from the intestines or feces as an inoculant and is more common in
monogastrics. In either case, transferring whole contents allows for the transfer of
bacteria, methanogens, protozoa, fungi, and viruses. Prebiotics are chemical or feed
additives which promote a healthy digestive function by improving and supporting the
growth of normal GIT microbiota [163, 181].
Probiotics and transfaunation have long been used to treat GIT dysfunction, especially
after surgery [182–185], but they are also popular as preventative methods to improve
overall health [175, 186–189]. For production animals, probiotics have been
administered to improve meat, milk, or wool output. This has been accomplished by
increasing fibrolysis in the rumen and, thus, dietary efficiency [149, 176–178, 187, 190–
194], or by reducing energy wasted in methanogenesis [82] and GIT dysfunction [183].
Rumen development in young ruminants is linked to colonization of the rumen.
Colonization begins during birth and progresses through to adulthood [195–198], after
which the rumen population may change with diet and health status, but is generally
considered to be stable [199, 200]. Host GIT epithelial cells will also adapt to normal
23
GIT microbiota. Host cells use pattern-recognition receptors to recognize conserved
microbial markers, and in response will activate pro- and anti-inflammatory responses as
well as upregulate epithelial cell signaling [201, 202]. Thus, alteration of the GIT
microbiota is difficult to achieve long-term, especially when the environment is colonized
by well-established and well-adapted microorganisms.
1.5 Summary
It was hypothesized that the moose would host novel microorganisms; that these
microorganisms would be capable of a wide variety of enzymatic functions; and that
these microorganisms could be used to improve other systems. The objectives of this
work were to identify the bacteria, archaea, and protozoa present in the rumen of moose;
to culture bacteria from the rumen of the moose in order to study their biochemical
capabilities; and to apply those cultured bacterial isolates to improve fiber digestion in
neonate lambs.
24
1.6 References
1. Cronin MA: Intraspecific variation in mitochondrial DNA of North American
cervids. J Mammal 1992, 73:70–82.
2. Hundertmark KJ, Bowyer RT, Shields GF, Schwartz CC: Mitochondrial
phylogeography of moose (Alces alces) in North America. J Mammal 2003, 84:718–
728.
3. Hundertmark KJ, Bowyer RT: Genetics, evolution, and phylogeography of moose.
Alces 2004, 40:103–122.
4. Alexander CE: The status and management of moose in Vermont. Alces 1993,
29:187–195.
5. Saether B-E: Annual variation in carcass weight of Norwegian moose in relation to
climate along a latititudinal gradient. J Wildl Manag. 1985, 49:977–983.
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42
1.7 Figures
Figure 1-1 Diagram comparing the immature ruminant to the mature ruminant.
Photo courtesy of http://veanavite.com.au/RearingGuide/Calves.aspx
Figure 1-2 The frequency of variability in the bacterial 16S rRNA gene [203].
Figure 1-3 Variable regions of the ciliate protozoal 18S rRNA.
Adapted from Ishaq and Wright, 2014 [122].
43
CHAPTER 2 INSIGHT INTO THE BACTERIAL GUT MICROBIOME OF
THE NORTH AMERICAN MOOSE (ALCES ALCES).
Suzanne L. Ishaq1,*
and André-Denis G. Wright1,2
¹ Department of Animal Science, College of Agriculture and Life Sciences, University of
Vermont, 570 Main St., Burlington, Vermont 05401
² Department of Medicine, University of Vermont, 111 Colchester Ave., Burlington,
Vermont, 05401
* Suzanne Ishaq, Department of Animal Science, University of Vermont, 203 Terrill
Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-802-656-
8196.
Email addresses:
SLI: slpelleg@uvm.edu
ADGW: adwright@uvm.edu
Keywords: colon/gut microbiome/rumen/Vermont/16S rRNA
Ishaq, S.L. and Wright, A-D.G. (2012). Insight into the bacterial gut microbiome of the
North American moose (Alces alces). BMC Microbiology, 12:212.
44
2.1 Abstract
Background: The work presented here provides the first intensive insight into the
bacterial populations in the digestive tract of the North American moose (Alces alces).
Eight free-range moose on natural pasture were sampled, producing eight rumen samples
and six colon samples. Second generation (G2) PhyloChips were used to determine the
presence of hundreds of operational taxonomic units (OTUs), representing multiple
closely related species/strains (>97% identity), found in the rumen and colon of the
moose.
Results: A total of 789 unique OTUs were used for analysis, which passed the
fluorescence and the positive fraction thresholds. There were 73 OTUs, representing 21
bacterial families, which were found exclusively in the rumen samples: Lachnospiraceae,
Prevotellaceae and several unclassified families, whereas there were 71 OTUs,
representing 22 bacterial families, which were found exclusively in the colon samples:
Clostridiaceae, Enterobacteriaceae and several unclassified families. Overall, there were
164 OTUs that were found in 100% of the samples. The Firmicutes were the most
dominant bacteria phylum in both the rumen and the colon.
Conclusions: Using PhyloTrac and UniFrac computer software, samples
clustered into two distinct groups: rumen and colon, confirming that the rumen and colon
are distinct environments. There was an apparent correlation of age to cluster, which will
be validated by a larger sample size in future studies, but there were no detectable trends
based upon gender.
45
2.2 Background
North American moose, (Alces alces), are the largest browsing ruminant of the
deer family Cervidae, and preferably inhabit young hardwood forests, deciduous mixed
forests, and salt rich wetland habitats that have an abundance of woody browse and salty
aquatic vegetation [1–4]. In northern latitudes, such as Vermont, moose have
traditionally done well, although unregulated hunting and deforested habitats caused a
severe decline in the Vermont population during the 20th
century [5]. It was not until
1993 that moose hunting became regulated again in Vermont and remains strictly
controlled by the state. Vermont provides a wide variety of habitats, with one of the most
suitable regions being in the northeastern corner of the state. Known as the Northeast
Kingdom, the area is rich in bogs and swamps, and is comprised of over 75% deciduous
or mixed forests with growth of various maturities [6]. This area also supports the
highest concentration of moose in the state [6] and traditionally has the highest hunter
success rates: ranging from 38-70% from 2006 to 2009 [7, 8], making it an excellent site
for sample collection.
Like all ruminants, moose have a specialized digestive system with a four
chambered stomach that allows a complex consortium of symbiotic microorganisms to
ferment plant matter that the animal cannot breakdown on its own, especially cellulose
[9, 10]. During the process of fermentation, hydrogen, ammonia, carbon dioxide, and
methane gas are produced [11], as well as volatile fatty acids (VFAs) such as acetate,
butyrate, and propionate. These VFAs are released into the rumen where they can be
absorbed and used by the ruminant as a source of energy [11–13].
46
Limited work has previously been done using classical microbiology to identify
organisms found in the rumen of moose [14]. One male moose from Alaska was shot in
August of 1985, and bacteria which were isolated and characterized consisted of
Streptococcus bovis (21 strains), Butyrivibrio fibrisolvens (9 strains), Lachnospira
multiparus (7 strains), and Selenomonas ruminantium (2 strains) [14].
For the present study, the second generation (G2) PhyloChip (PhyloTech Inc.,
California) was used to survey rumen and colon samples for the presence and
presumptive identification of bacteria. The G2 PhyloChip uses 16S rRNA gene
sequences to rapidly type bacteria and methanogens in a mixed microbial sample without
the use of cloning or sequencing [15, 16]. The PhyloChip contains approximately
500,000 probes on its surface, representing over 8,400 species of bacteria and roughly
300 species of archaea [17]. There are 11, 25mer, probes that are designed to hybridize
to each specific taxon, allowing for specificity in determining taxa present [17].
Depending on what the probes are designed to target, the PhyloChip can be used to
differentiate between different serotypes of Escherichia coli, or determine the presence of
a species regardless of strain. It is already a popular bacterial screening method for air
[15], water [18], and soil [19, 20], and has recently gained favor for digestive tract
samples [21, 22]. Due to their specificity and sensitivity, DNA microarrays have also
been used to categorize diseased and healthy states [22, 23].
The major objectives of the present study were to type the bacteria present in
rumen and colonic samples, and to compare these findings with other studies of
ruminants and herbivores. Given that moose are large browsing herbivores [3], it was
hypothesized that the bacterial populations in the browse-fed wild moose would be more
47
closely related to bacterial populations found in other browse/forage fed animals. This
study reports on the bacteria found in the rumen and colon of the North American moose,
as well as how these environments relate to other studies of the gut microbiome in
various species.
2.3 Results
2.3.1 Quantitative Real-Time PCR
Mean bacteria cell densities were calculated for each rumen sample using
standard curves generated by Bio-Rad’s CFX96 software. Based on a regression line
created using the bacterial standards (R2= 0.997), estimated cell density ranged from
8.46 x 1011
to 2.77 x 1012
copies of 16S rRNA/g in the rumen (Table 1).
2.3.2 PhyloChip Array
1.1.2.2.Combined rumen and colon
A total of 789 unique OTUs were used for analysis which passed the fluorescence
and the positive fraction thresholds. Total numbers for each taxonomic group found are
listed for each sample (Table 2), which represent raw data before initial screening. There
were 789 total distinct OTUs that were found in all the samples combined; 267
Firmicutes, 225 Proteobacteria, and 72 Bacteroidetes being the major phyla. Not all
OTUs were found in every sample, but out the total 789 OTUs there were 164 OTUs,
comprising 25 bacterial families, which were found across all 14 samples (Figure 1). The
most abundant of these families were unclassified, 25%; Lachnospiraceae, 20%;
Clostridiaceae, 16% and Peptostreptococcaceae, 7%. The remaining 21 families
48
represented less than 4% each of the OTUs found in all 14 samples (Figure 1). The
OTUs with unclassified families were then classified by phyla; of the 25% of OTUs with
unclassified families, the phyla Firmicutes represented 22%, Proteobacteria and
Chloroflexi were 17% each, Bacteroidetes was 15%, and all others represented 5% or less
(Figure 2a).
Many of the unclassified sequences were presumptively identified in PhyloTrac,
as well as in GenBank, based upon the environment where they were found as most of
them are uncultured, thereby providing an interesting, if subjective, means of
comparison. Unclassified sequences in the moose were related to a range of
environmental sequences including 102 “termite gut clone” OTUs, 20 “rumen clone”
OTUs, 20 “forest soil/wetland clone” OTUs, 16 “swine intestine/fecal clone” OTUs, six
“human colonic clone” OTUs, six “sludge clone” OTUs, four “penguin dropping clone”
OTUs, four “chicken gut clone” OTUs, two “human mouth clone” OTUs and a large
number of “soil clone” and “water clone” OTUs from various environments. While
many of the forest soil/wetland, soil and water clones may represent transient populations
that are picked up from the environment, these data correlate with summer diets of moose
in Vermont, namely woody browse in forested areas and aquatic plants found in bogs and
marshes.
1.1.2.3. Rumen Samples
The rumen samples contained 575 total OTUs; 192 Firmicutes, 142
Proteobacteria, and 66 Bacteroidetes being the dominant phyla. In the rumen samples,
there was a range of 308 to 465 OTUs/sample, and an average of 350 OTUs/sample
49
(Table 2). There were 237 OTUs found across all eight rumen samples and, of these, 73
OTUs were exclusive to the rumen, representing 21 families (Figure 3). The OTUs with
unclassified families were assigned by phyla (Figure 2b), with the dominant phyla being
Bacteroidetes, 27%; Proteobacteria, 19%; and Chloroflexi and NC10 with 11% each.
NC10 is a candidate phylum consisting of uncultivated and uncharacterized bacteria that
is currently named after the location where the bacteria were sampled, Nullarbor Caves,
Australia. All other phyla represented 10% or less of OTUs with unclassified families
(Figure 2b). Of the unclassified sequences found exclusively in the rumen, there were 51
termite gut clones, 36 marine, wetland, or waterway sediment clones, 13 fecal or colon
clones, 11 rumen clones, nine soil clones, and seven sludge clones.
A previous study on rumen microorganisms in the moose [14] identified
Streptococcus bovis (21 strains), Butyrivibrio fibrisolvens (9 strains), Lachnospira
multiparus (7 strains), and Selenomonas ruminantium (2 strains). The present study
found Streptococcus bovis strains ATCC 43143 and B315 in every sample except for 1C
and 2R. Butyrivibrio fibrisolvens and B. fibrisolvens strain LP1265 were found in all
samples except for 3R, 6R, 2C and 3C, whereas Butyrivibrio fibrisolvens strain WV1 was
found in 8C only. Lachnospira multiparus was not present on the chip. However, all 14
samples did contain Lachnospira pectinoschiza, as well as Selenomonas ruminantium
strains S20 and JCM6582.
1.1.2.4. Colon samples
The colon samples contained a total of 658 OTUs; 248 Firmicutes, 194
Proteobacteria and 46 Bacteroidetes. The colon samples ranged from 307 to 597
50
OTUs/sample, with an average of 413 OTUs/sample (Table 2). There were 235 OTUs
that were found across all six colon samples, and of these, 71 OTUs were exclusive to the
colon, representing 22 families (Figure 3). Again, the OTUs with unclassified families
were assigned by phyla (Figure 2c), with the dominant phyla being Firmicutes,
Proteobacteria and Unclassified, 16% each; Gemmatimonadetes and Chloroflexi, 11%
each, and Bacteroidetes, 10%. All other phyla represented 10% or less of OTUs with
unclassified families (Figure 2c). Again, many unidentified sequences were listed as
uncultured clones by location found. The unidentified sequences found exclusively in the
colon were related to52 “termite gut clone” OTUs, 20 “marine, wetland, or waterway
sediment clone” OTUs, 10 “soil clone” OTUs, eight “fecal/colon clone” OTUs, eight
“sludge clone” OTUs and five “rumen clone” OTUs.
2.3.3 UniFrac analysis
P-test significance was run using all 14 samples together and 100 permutations,
resulting in a corrected p-value of < 0.01, designating that each sample was significantly
different from each other. Environment clusters and jackknife values are provided
(Figure 4), showing a statistical measurement of the correctness of the tree created. The
weighted algorithm accounted for the relative abundance of sequences in a sample, which
is typical for environmental samples. UniFrac and PhyloTrac both clustered the rumen
and colon samples into two distinct groups: the first node was present 100% of the time
in the unweighted and weighted UniFrac clusters. The branching pattern for the rumen
group is different between UniFrac algorithm (Figure 4) and between programs (Figure
5). However, the branching pattern for the colon group is identical between PhyloTrac,
51
and the unweighted and weighted UniFrac outputs. A principal component analysis
(PCA) scatterplot (Figure 5) was also created using the weighted algorithm, which
grouped the rumen and colon samples separately.
The rumen samples also tentatively clustered by age/weight in the unweighted
UniFrac output (Figure 4a), with the youngest/lightest two grouped together (185 kg., 1-
yr old; 186.36 kg, 2-yrs old), the two 3-yr old females, grouped together (244.55 and
259.55 kg), and the three oldest/heaviest males (301.36 kg, 4-yrs old; 319.09 kg, 4-yrs
old; and 405.45 kg, 8-yrs old) grouped together with a male of unspecified age/weight.
The age/weight clusters within the rumen in the weighted UniFrac output (Figure 4b)
were not the same as with the unweighted output, nevertheless, some clusters remained
(c.f. Figures 5a and 5b).
2.4 Discussion
The major objective of this study was to identify bacteria present in the rumen and
colon content samples of the North American moose. This is the first time that the rumen
and colon bacterial populations of the moose have been evaluated on a large scale (i.e.
PhyloChip), with the last work published in 1986 [14]. While Dehority’s [14] results
give the present study an indication of the bacterial population within the rumen of
moose, the findings were limited by a sample size of one animal and the constraints of
classical microbiology. Anaerobic gut microorganisms are difficult to culture, which
continues to present a major obstacle in gut microbial identification. However, genetic
analysis, such as microarray and high-throughput sequencing, allow microbes to be
studied before they are grown in a pure culture.
52
One drawback of using the PhyloChip, and indeed with all methods that forego
culturing, is the inability to distinguish between live and dead microbes. It also cannot
distinguish between colonizing versus transient species, such as the green sulfur bacteria
in the phylum Chlorobi or green non-sulfur bacteria of Chloroflexi, both of which are
photosynthetic and picked up by the moose during feeding. Careful analysis of the data
is required to properly interpret the results. However, even dead and transient bacterial
populations can have a profound impact on the resident bacteria as well as the host,
whether by releasing harmful components when lysed, such as Lipid A, or providing
DNA which may be taken up by live cells in the rumen, as in plasmids that contain genes
that confer antibiotic resistance. Is important to take a holistic view to prevent
marginalizing potentially important species. Like all methods that rely on PCR
amplification, PhyloChip is also subject to PCR bias. This is mediated during sample
preparation by running multiple reactions per sample and minimizing the number of
cycles.
Rumen samples were consistently clustered separately from the colon samples by
PhyloTrac and UniFrac and there were 174 OTUs that were exclusive to either the rumen
or the colon; confirming that the rumen and the colon are two distinct environments.
Similar findings were reported in a study using fecal samples from sheep [24], as a non-
invasive means of modeling the rumen bacteria from captive exotic animals where it is
impractical to obtain rumen contents. It was concluded that bacterial concentrations and
species in the colon were not reliably predictive of the bacterial concentrations or species
in the rumen [24].
53
The rumen contained an average of 1.66 x 1012
copies of 16S rRNA/g (± 7.27 x
1011
SEM). This is comparable to other ruminants: 5.17 x 1011
cells/g (± 3.49 x 1011
) for
Norwegian reindeer [25], 1.86 x 1011
cells/g (± 9.68 x 1010
) and 5.38 x 1011
cells/g (±
2.62 x 1011
) for Svalbard reindeer [26] in April and October, respectively, and 1.60 x 1011
cells/g (± 1.35 x 1011
) for Canadian dairy cattle [27].
The dominant phylum in the moose rumen was Firmicutes with 192 OTUs,
followed by Proteobacteria with 142 OTUs and Bacteroidetes with 66 OTUs. Firmicutes
is often the dominant phylum in gut microbiomes, and many of those found in the moose
were of the class Clostridia, containing sulfate-reducing bacteria (SRB), which can be
pathogenic, endospore forming, and found in soil. Sundset et al. [28] reported that in
rumen samples taken from reindeer in Svalbard, the bacteria cultivated were mainly from
the class Clostridia. It was noted that Fibrobacter succinogenes, Ruminococcus albus,
and R. flavefaciens were not found in the rumen of the reindeer [28], although this may
simply be a bias of the cultivation approach. Fibrobacter and Ruminococcus are both
cellulolytic and have previously been found in the rumen of reindeer [25, 29]. However,
in the present study, F. succinogenes and R. albus were not found, despite both species
being present on the chip with multiple strains. Ruminococcus flavefaciens was detected
in several samples, but only a few of its 11 probes matched, making the result
insignificant. Ruminococcus obeum was detected in the present study.
In a recent paper studying rumen bacteria in dairy cattle, Firmicutes was the
dominant phylum in four cattle rumen samples when using full length 16S rRNA clone
libraries, but was only dominant in three samples with Proteobacteria being dominant in
one sample when using partial 16S rRNA clone libraries or environmental gene tags [30].
54
Gamma- and alpha-Proteobacteria have been shown to be type I and type II
methanotrophs, respectively, meaning they utilize methane as their source of carbon. In
the present study, the species Enterobacter cloacae, of the class gamma-Proteobacteria,
was found in the moose, and in a non-lactating Holstein cow based on PCR of the 16S
rRNA gene to target methanotrophs [31].
In a comparison between the moose rumen data and a study using the PhyloChip
and samples from the crop of the wild folivorous bird, the hoatzin [21], similarities arise.
Godoy-Vitorino et al. [17] showed that bacteria from the crop of the hoatzin clustered
into distinct groups by age: chicks (n=3), juveniles (n=3) and adults (n=3). This
correlates with the present study, as the rumen samples clustered by age/weight in the
unweighted, and to some extent, in the weighted UniFrac jackknife clustering. As in the
moose, some of the differential families found in the crop of the adult hoatzin included
Lachnospiraceae, Acidobacteriaceae, Peptostreptococcaceae, Helicobacteraceae and
Unclassified (phyla: Proteobacteria, Cyanobacteria, NC10, Chloroflexi, etc.) [17]. The
total number of taxonomic groups discovered for hoatzin chicks, juveniles and adults
ranged from 37-40 phyla, 47-49 classes, 88-90 orders, 147-152 families, 305-313
subfamilies, and 1351 to 1521 OTUs, an increase over moose, which possibly arises from
grouping three samples onto one chip, as was done with the hoatzin samples [21].
In the study by Godoy-Vitorino et al. [21], as well as the current study, OTU
cutoff level was predetermined by the PhyloTrac program (i.e. <97%). However, Godoy-
Vitorino et al. [17] used a pf=0.90 to determine if an OTU was present, meaning that
90% of the probes for that OTU were positive. When a pf value of 0.90 was applied to
the current study, effectively lowering the number of probes that needed to be positive to
55
be a match for that OTU, the average number of OTUs present rose from 350 to 488 for
the rumen and from 413 to 524 for the colon. This suggests that moose either have only a
relatively few bacterial species in large quantities, or that there is a wide variety of
bacteria found in the moose which are unique and unable to hybridize to the probes found
on the G2 PhyloChip. The PhyloChip has recently been shown to overestimate species
diversity [32]. The major drawback to using DNA microarray chips is that only known
sequences can be used as probes, thus rendering the chips ineffective for discovering and
typing new species [33]. The G2 PhyloChip was created in 2006, thus any new taxa that
have been identified since then will not be present on the chip, and any re-classification
of sequences that are currently on the chip can only be noted by using the most current
version of PhyloTrac. These data will be validated and expanded upon using high-
throughput DNA sequencing and cultures.
Despite the many similarities between bacteria found in the rumen of the moose
to the hoatzin, reindeer and the previous moose study, there are many bacterial families
found in the present study which were not mentioned in any of the previous studies.
However, many of these bacterial families have been noted in the foregut of the
dromedary camel, a pseudo-ruminant with a three chambered stomach. In a recent study
by Samsudin et al. [34], the following bacterial families were found in the foregut
dromedary camels (n=12) as well as the rumen of the moose in the present study (though
not in every rumen sample): Eubacteriaceae, Clostridiaceae, Prevotellaceae,
Lachnospiraceae, Rikenellaceae, Flexibacteraceae, Bacteroidaceae, Erysipelotrichaceae,
Bacillaceae, Peptococcoceae, and Peptostreptococcaceae. Wild dromedary camels in
Australia survive on a high fiber forage diet [34], which is closer to the diet of wild North
56
American moose. This may explain why the bacterial populations in wild camels appear
to be closer to moose than that of wild reindeer, which eat a diet rich in lichens, despite
the reindeer and the moose being members of the Cervidae family.
In the rumen, there were 51 sequences found that were listed as being related to
termite gut clones, yet many more similarities can be found between the moose and the
termite gut, which have compartmentalized guts containing microbes. Treponema
primitia strain ZAS-1, as well as five other Treponema species, were found in the moose
rumen in the present study, and 109 Treponema phylotypes and species were previously
found in the termite gut [35]. Treponema primitia, belonging to the phylum Spirochetes,
is an acetogenic microorganism capable of degrading mono- and disaccharides such as
cellulose or xylan [35]. Bacteroidetes, Chlorobi, Cyanobacteria, Firmicutes and
Proteobacteria clones were also discovered in the termite [35], as well 49 phylotypes
which represented three new candidate orders in the phylum Fibrobacteres.
To our knowledge, no studies exist using PhyloChip analysis on the fecal samples of
herbivores. However, many other colon studies exist, focusing on medically significant
pathogens in humans. In a recent study on irritable bowel syndrome, the bacterial
families in healthy rats were Rhizobiaceae, Peptococcaceae/Acidaminocoocus,
Clostridiaceae, Lachnospiraceae, Intrasporangiaceae, Succinivibrionaceae,
Alteromonadaceae, Paenibacillaceae and Flavobacteriaceae [36]. Of these, only
Peptococcaceae/Acidaminocoocus, Clostridiaceae and Lachnospiraceae were found in the
moose. In a separate study, fecal samples from cervid species in Norway were tested for
colon bacteria that were known pathogens to humans using selective culturing techniques
[37]. In that study, E. coli O103 was found in 41% of the samples, E. coli O26 and O145
57
were found in small amounts, and E. coli O111 and O157 were not found at all [37]. In
addition, no cervid fecal samples were positive for Salmonella, although one roe deer
(Capreolus capreolus) sample was positive for Campylobacter jejuni jejuni [37]. In the
present study, several samples contained Salmonella, E. coli, or Campylobacter species,
although no strains of verocytotoxic (e.g. O157:H7) or uropathogenic (e.g. CFT073) E.
coli, Shigella or Campylobacter jejuni were found. However, all of the moose colon
samples contained Citrobacter freundii, a nitrate reducing bacteria commonly found in
the environment, which is known to be an opportunistic pathogen in humans.
The moose colon contained 658 OTUs, of which 248 were Firmicutes and 46
Bacteroidetes. In a 2006 study of the mouse gut microbiome in lean and ob/ob obese
mice, it was discovered that transfaunation with microorganisms from the obese mouse
intestine into the lean mice caused increased weight gain and fat deposition [38]. It is
important to note that the bacteria in the obese mice had significantly higher proportions
of Firmicutes than Bacteroidetes [38].
The work presented here provides the first insight into the bacterial populations in
the digestive tract of the North American moose. While the G2 PhyloChip is an excellent
tool for identifying known bacteria, it contains only 300 archaeal sequences, which were
not utilized because bacterial-specific primers were used. Furthermore, there is currently
no microarray that is designed to identify protozoa or fungi. Next generation (high-
throughput) sequencing is needed to validate the bacterial population findings of the
present study, as well as identify the protozoal, archaeal and fungal populations present in
the moose rumen. The PhyloChip, like all methods that do not rely on culturing, cannot
be used to differentiate between transient and colonizing species. It can be assumed that
58
some species found in the moose are simply passing through the digestive tract, having
been picked up from the environment, and are not colonizing the tract. Despite this, these
transient bacteria may still have an impact on the dynamics within the rumen, and it is
important to take a holistic approach when looking at mixed environmental samples. It is
also possible that some of these unclassified bacteria which are presumed transient, such
as the soil or water clones, are actually colonizing the moose digestive tract and are
simply unique to moose.
2.5 Materials and Methods
2.5.1 Sample Collection
All samples were obtained with permission of licensed hunters through the
Vermont Department of Fish and Wildlife. Whole rumen (R) and colon (C) contents
were collected from moose shot during the October 2010 moose hunting season in
Vermont. Samples were collected by hunters within 2 h, if not sooner, of death and put
on ice immediately. Hunters were given a written set of instructions about sample
collection, and had been instructed verbally as well, to fill the collection containers with
material taken from well inside the rumen and colon, and to seal the container quickly to
minimize overexposure to oxygen. Samples were then transferred to the laboratory
within 24 h, and stored at -20ºC until DNA extraction. A total of eight rumen and six
colon samples (Table 3) were collected from eight moose. Twelve of the samples were
paired rumen and colon contents from the same animal, and two rumen samples did not
have corresponding colon samples. Moose were weighed and aged, by examining the
59
wear and replacement of the premolars and molars of the lower jar, by Vermont Fish and
Wildlife biologists at the mandatory reporting stations.
2.5.2 DNA extraction
Samples were fully thawed, and 0.25 gram aliquots of either rumen content or
colonic material, were used for extraction. DNA was extracted from all 14 samples using
the repeated bead-beating plus column (RBB+C) method [39], and the QIAamp DNA
Stool Mini Kit (QIAGEN, Germantown, Maryland). DNA was quantified using a
NanoDrop 2000C Spectrophotometer (ThermoScientific, California), and the purity of
the DNA extract was verified using gel electrophoresis to molecular weight. DNA
extract was also PCR amplified to test quality and verified using gel electrophoresis to
determine correct PCR amplicon length prior to quantitative real-time PCR, or
hybridization to the PhyloChip.
2.5.3 Quantitative Real-Time PCR
Real-time PCR was used to calculate bacterial concentrations in each sample, and
was performed using a CFX96 thermocycler (Bio-Rad, Hercules, CA), using universal
bacterial primers 1114-F (5’-CGGCAACGAGCGCAACCC-3’) and 1275-R (5’-
CCATTGTAGCACGTGTGTAGCC-3’) [40]. Each reaction contained 12.5μL of the iQ
SYBR Green Supermix kit (Bio-Rad, Hercules, CA): 2.5µl of each primer (40mM),
6.5µL of ddH2O, and 1µL of the initial DNA extract which was diluted to approximately
10 ng/μL. The external standard for bacteria, as previously described [40], was a mix of
Ruminococcus flavefaciens and Fibrobacter succinogenes that were serially diluted over
60
four logs. The protocol consisted of an initial denaturing at 95°C for 15 min, then 40
cycles of 95°C for 30s, 60°C for 30s, 72° for 1 min. This was followed by a melt curve,
with a temperature increase 0.5°C every 10s from 65ºC up to 95°C to check for
contamination. Data were analyzed using the CFX Manager Software v1.6 (Bio-Rad,
Hercules, CA).
2.5.4 PhyloChip
DNA (25-50 ng/μl) was sent to the University of Vermont’s Microarray Core
Facility for genotyping using the G2 PhyloChip (PhyloTech Inc., San Francisco, CA).
There, the 16S rRNA gene of bacteria was PCR amplified using the universal bacterial
primers 27F (5’-AGAGTTTGATCCTGGCTCAG-3’) and 1492R (5’-
CTACGGCTACCTTGTTACGA-3’) [41], quantified, fragmented, labeled with biotin,
and hybridized according to manufacturer’s proprietary instructions. Each amplified
sample was hybridized to its own chip, creating 14 total data sets. The analysis platform
used was an Affymetrix 7G scanner, and Gene Chip Operating System (GCOS). Data
generated is available online at ARRAYExpress.
2.5.5 Analysis
PhyloChip data were analyzed using the software program PhyloTrac v2.0
(available from www.phylotrac.org). PhyloTrac automatically removed background
noise as the average of the two least intense fluorescence signals in each chip quadrant,
and used internal standards to create a linear scale to normalize fluorescence intensity
with concentration of that sequence in the original sample [17]. The 16S rRNA
61
sequences on the chip were grouped into Operational Taxonomic Units (OTUs) based on
a 97% or greater sequence identity, which was predetermined by the program. For each
OTU, there are 11 perfect-match probes, and 11 mismatch probes, which are always
analyzed in pairs. For an OTU to be considered a positive match to a probe, the signal
intensity must be 1.3X the intensity of the mismatch probe [13]. The positive fraction is
a measure of how many perfect-match probes matched out of the total number of probe
pairs for that OTU. For this study, a positive fraction of 0.92 was used to determine the
presence of an OTU in a sample; for each OTU, 92% of the perfect-match probes were
positive. A mean intensity threshold of 100 was used, so that only OTUs with signal
intensity greater than that were included in the analysis. All 14 sample files were used in
the comparison.
Data were evaluated down to the taxonomic level of family for most analyses
since each OTU represented more than one species [32]. A heatmap (Figure 6) showing
the presence or absence, and relative intensity of each OTU was created using all 14
samples. Samples were arranged in rows and were clustered on the vertical axis. OTUs
were arranged vertically and were clustered on the horizontal axis. Clustering was done
using PhyloTrac’s heatmap option with Pearson correlation, a measure of the correlation
between two variables, and complete linkage algorithms (farthest neighbor), which
clusters based on the maximum distance between two variables.
UniFrac (available from http:// bmf2.colorado.edu/unifrac/), an online statistical
program, was used to analyze PhyloChip data [42, 43] and to confirm the clustering
functions of PhyloTrac. Data were exported from PhyloTrac for analysis using the
UniFrac statistical software. P-test significance was run using all 14 environments
62
together and 100 permutations, to determine whether each sample was significantly
different from each other. A p-value of < 0.05 states that the environments were
significantly clustered together. Two Jackknife environment clusters were performed
using 100 permutations, the weighted and unweighted UniFrac algorithms, and 307
minimum sequences to keep (UniFrac default for the specified conditions). Jackknife
counts were provided for each node, representing the number of times out of 100 that a
node was present on the tree when the tree was repeatedly rebuilt. A Jackknife
percentage of >50% is considered significant. A principal component analysis (PCA)
scatterplot was also created using the weighted algorithm, a chart which arranged two
potentially related variables into unrelated variables on a graph, revealing underlying
variance within the data.
2.6 Competing Interests
The authors declare no competing interests.
2.7 Authors’ Contributions
SI carried out all DNA extraction, PCR, PhyloTrac and Unifrac analysis, and drafted the
manuscript. AW conceived of the study and participated in its design, and edited the
manuscript. Both authors approved the final manuscript.
2.8 Acknowledgements
The author would like to acknowledge Rachel P. Smith and Dr. Benoit St-Pierre,
Department of Animal Science, University of Vermont, for technical advice; the Vermont
63
Fish and Wildlife Department for their help in sample collection logistics; and Terry
Clifford, Archie Foster, Lenny Gerardi, Ralph Loomis, Beth and John Mayer, and Rob
Whitcomb for collection of samples.
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2.10 Figures
Figure 2-1 The OTUs found common in all samples (rumen and colon).
164 OTUs found common to all samples (n=14). The Unclassified sections are broken down by phyla in
Figure 2a.
68
Figure 2-2 Breakdown of unclassified families by phylum.
(a) OTUs present in all 14 samples. There were 41 OTUs found exclusively in the rumen that were not
classified down to the family level. (b) OTUs found exclusively in the rumen. There were 22 OTUs found
exclusively in the rumen that were not classified down to the family level. (c) OTUs found exclusively in
the colon. There were 19 OTUs found exclusively in the colon that were not classified down to the family
level. Several are candidate phyla and are named by where they were discovered: AD3, soil in Virginia
and Delaware, USA; OP3 and OP10, now Armatimonadetes, Obsidian Pool hot spring in Yellowstone
National Park, USA; NC10, Null Arbor Caves, Australia; TM7, a peat bog in Gifhorn, Germany; WS3, a
contaminated aquifer on Wurtsmith Air Force Base in Michigan, USA.
69
Figure 2-3 A comparison of the OTUs exclusive to the rumen or the colon.
A comparison of the 73 OTUs exclusive in the rumen (n=8) or 71 OTUs exclusive in the colon (n=6), by
family. Families with three or more associated OTUs are labeled in the chart; all other families with two or
fewer OTUs are labeled via the legend. The Unclassified sections are broken down by phyla in Figure 2b,
and 2c, respectively.
70
Figure 2-4 Jackknife environment clustering in UniFrac, by sample.
(a) An unweighted UniFrac algorithm and (b) a weighted UniFrac algorithm were used, and were not
normalized as different evolutionary rates of gene did not need to be accounted for. Jackknife counts for
each are provided for each node. The weighted UniFrac algorithm takes into account abundance of
sequences, and is better suited to analysis of mixed bacterial samples. Samples are labeled by individual
moose (1-8) and sample type (rumen, R or colon, C), and gender, weight and age information is provided in
the legend.
71
Figure 2-5 Principal component analysis (PCA) scatterplot of the environments using the weighted
UniFrac algorithm.
Samples are labeled by number (1-8), and groups are shown.
72
Figure 2-6 Distribution of PhyloChip OTU’s for all 14 samples.
Samples (rumen and colon) are arranged in rows and are clustered on the vertical axis (y-axis). OTU’s are
arranged vertically and are on the horizontal axis (x-axis). Clustering was done for each using PhyloTrac’s
heatmap option with Pearson correlations and complete linkage algorithms.
73
2.11 Tables
Table 2-1 Estimated densities (16S rRNA copy numbers per gram wet weight) of bacteria in the
rumen (R) of the moose in October, 2010, Vermont.
All figures based on calculations using standard curves generated by the Bio-Rad CFX manager program:
bacteria (R² = 0.997).
Sample Bacterial copies of 16S rRNA/g (SEM)
1R 8.46 x 1011
2R 1.61 x 1012
3R 2.57 x 1012
4R 2.02 x 1012
5R 9.36 x 1011
6R 1.21 x 1012
7R 2.77 x 1012
8R 1.34 x 1012
Mean (SEM) 1.66 x 1012
(7.27 x 1011
)
74
Table 2-2 Total number of taxa found in each sample, before screening for analysis but after
background noise was removed and including only OTUs with > 0.92 positive fraction.
Not all OTUs were found in every sample.
Sample Phylum Class Order Family Sub-family OTU
1R 20 42 59 83 94 367
2R 21 43 63 90 103 395
3R 19 38 51 75 83 308
4R 23 44 58 80 94 374
5R 23 46 67 97 109 465
6R 23 43 56 84 97 382
7R 22 43 57 86 100 379
8R 23 45 69 98 116 432
Mean rumen 22 43 60 87 100 350
1C 16 33 45 63 72 331
2C 18 36 54 78 90 378
3C 15 30 40 54 65 307
6C 17 34 50 72 84 374
7C 26 49 82 124 146 597
8C 21 42 66 98 115 488
Mean colon 19 37 51 82 95 413
Table 2-3 Statistics for samples taken from moose shot in October 2010 in Vermont during the moose
hunting season.
Moose Sample
location
Sample
name
Gender Weight,
dressed carcass (kg)
Approx.
age (yr)
1 Rumen 1R
F 185 1 Colon 1C
2 Rumen 2R
F 244.55 3 Colon 2C
3 Rumen 3R
M 186.36 2 Colon 3C
4 Rumen 4R M N/A N/A
5 Rumen 5R M 319.09 4
6 Rumen 6R
F 259.55 3 Colon 6C
7 Rumen 7R
M 301.36 4 Colon 7C
8 Rumen 8R
M 405.45 8 Colon 8C
75
2.12 Supplemental Material
Supplementary Table 1 Genus/Identifier and GenBank # of sequences in selected
families, found in all rumen samples (n=8), sequences are non-exclusive to the rumen.
Rumen
Genus or Identifier GenBank ASCN #
Clostridiaceae
Clostridium X71852.1, AB093546.1
cow rumen clone AY244908.1
Great Artesian Basin clone AF407695.1
Forested wetland clone AF523923
Lachnospiraceae AF550610.1
Oral clone AF481208.1
sludge clone AF482434.1
Swine intestine clone AF371790.1, AF371796.1
Termite gut clone
AB100478.1, AB100483.1, AB100493.1, AB100479.1,
AB100476.1, AB100486.1, AB089030.1, AB089043.1,
AB089045.1, AB088977.1, AB089028.1, AB088965.1,
AB088951.1, AB089035.1, AB088984.1, AB089032.1
Lachnospiraceae
Butyrivibrio U41168.1, X89978.1, AF105403.1, AY178635.1
chicken clone AF376201.1, AF376218.1
Clostridium AF067965.1, AY169415.1
Eubacterium AB008552.1
Fusobacterium X85022.1
Granular sludge clone AF332711.1, AF332720.1, AF332721.1
human colonic clone AJ408957.1, AJ408972.1, AJ408993.1, AJ408989.1
Lachnospira AY169414.1
Pseudobutyrivibrio AF202260.1
Swine intestine clone AF371584.1, AF371541.1, AF371648.1
Rumen clone AB034003.1, AB034059.1
Termite gut clone
AB100463.1, AB089002.1, AB088983.2, AB088950.1,
B088993.1, AB088990.1, AB088989.1, AB088998.1,
AB088994.1, B089044.1, AB088968.1, AB088980.1,
AB088952.1, AB089040.1, B088991.1, AB089034.1
Peptostreptococcaceae
Anaerococcus AF542229.1
Finegoldia AB109771.1
municipal wastewater
treatment plant clone CR933145.1
76
oral clone AF538856.1, Y134903.1, AY134904.1
Peptostreptococcus AF481225.1
TCE-dechlorinating clone AY217429.1
termite gut clone
AB100461.1, AB062845.1, AB088986.1, AB088954.2,
AB088971.1, AB088960.2, AB088970.1
Prevotellaceae
Cow rumen clone AY244919.1, AY244931.1, AY244923.1, AY244900.1
Deep marine sediment clone AY093462.1
Prevotella AY699286.1, AY134905.1, AF481227.1
Rumen clone AB185583.1
Swine intestine clone AF371893.1
Unclassified
Arthrobacter X80744.1
Bacillus AF454298.1
Beta proteobacterium,
uncultured AY082479
chicken cecum clone,
uncultured AF376430
Chlorobi, uncultured AY118151.1
coal effluent wetland clone AF523883.1, AF523884.1
cow rumen clone AY244902.1
Cryptoendolith AY250886.1
DCP-dechlorinating clone AJ306749.1, AJ306746.2, AJ306774.1, AJ306741.2,
AJ306793.1
deep marine sediment clone AY093480.1
Delaware River estuary
clone AY274839.1
Desulfotomaculum AY084078.1, Y11573.1, Y11574.1
Elbe river clone AJ401113.1
Feedlot manure, uncultured AF317384.1
Flexistipes AF481216.1
forest soil clone AY913277.1
forested wetland clone AF523973.1, AF524015.1
G+C Gram-positive clone AF465653.1
Holophaga AJ519640
human mouth clone AY207065.1, AY134895.1
hydrothermal vent sediment
clone AF420340.1
marine sediment above
hydrate ridge clone AJ535231.1
Mono Lake clone AF507879.2, AF507860.1, AF507869.2, AF507859.1,
AF507862.1, AF507892.1
77
ocean soil, uncultured AY181050.1
Paralvinella AJ441239.1, AJ441217.1
penguin droppings sediments
clone AY218551.1
Pleurotus AY838556.1
Rocky Mountain alpine soil
clone AY192275.1 AY192273.1
rumen clone AB185532.1
sludge clone AB106352.1, AF234699.1, AF368184.1
soil clone AJ390463.1
sponge clone AJ347025.1, AJ347055.1
temperate estuarine mud
clone AY216458.1
termite gut homogenate
clone
AB088930.1, AB089097.1, AB089109.1, AB089122.1,
AB089008.1
Toolik Lake clone AF534435.1
trichloroethene-
contaminated site clone
AF529128.1
uranium mill tailings waste
clone
AJ519669.1, AJ519650.1, AJ296549.1, AJ518784.1,
AJ519396.1, AJ536867.1
vadose (subterranean water)
clone AY177763.1
vent worm enrichment clone AJ431235.1
78
Supplementary Table 2 Genus/Identifier and GenBank # of sequences in selected
families, found in all colon samples (n=6), sequences are non-exclusive to the colon.
Colon
Genus or Identifier GenBank ASCN #
Clostridiaceae
Chicken intestine clone,
uncultured AF429381.1
Chlorobenzene-degrading
clone AJ488075.1
Clostridium AY007244.1, X76750.1, X71852.1, AB093546.1
Cow rumen clone AY244908.1
Clostridiales oral clone AF481208
Equine intestine clone AJ408137.1
Forested wetland clone,
uncultured AF523923
Granular sludge clone AY261814.1, AF482434.1
Great Artesian Basin clone AF407695.1
Lachnospiraceae AF550610.1
Swine intestine clone AF371796.1, AF371790.1, AF371783.1
Termite gut clone
AB100493.1, AB100478.1, AB088977.1, AB100475.1,
AB100479.1, AB089043.1, AB089028.1, AB100486.1,
AB088951.1, AB088965.1, AB089045.1, AB089032.1,
AB100469.1, AB100483.1, B089035.1,AB089033.1,
AB088984.1, AB100476.1, AB089030.1
Enterobacteriaceae
Alterococcus AF075271.2
Citrobacter AF025365.1
Coal effluent wetland clone AF523903.1
Enterobacter AJ550468.1
Erwinia AF141891.1, AF373202.1
Escherichia NC_000913.2
Klebsiella X93216.1
Kluyvera AJ627202.1
Opitutus AY695840.1
Pantoea AF130912.1, AF373198.1
Raoultella AF181574.1
Salmonella U92194.1
Serratia AF124036.1
Soda lake clone, uncultured AF507000.1
White-tail deer rumen clone AF084835.1
Lachnospiraceae
79
Butyrivibrio U41168.1
Clostridium * AY169415.1
Chicken clone, uncultured AF376205.1, AF376218.1, AF376201.1
Fusobacterium X85022.1
granular sludge clone AF332721.1, AF332720.1, AF332711.1
human colonic clone AJ408972.1, AJ408989.1
Lachnospira AY169414.1
Roseburia AY804149.1
Rumen clone AB034059.1, AB034003.1
Ruminantium AB008552.1
Swine intestine clone AF371584.1, AF371541.1, AF371648.1
Termite gut homogenate
clone
AB088950.1, AB089040.1, AB088950.1, AB088990.1,
AB088998.1, AB088993.1, AB100463.1, AB088994.1,
AB089002.1, AB089000.1, AB089044.1, AB088952.1,
AB089036.1, AB089034.1, AB088983.2, AB088980.1,
AB088968.1, AB088991.1
Peptostreptococcaceae
Anaerococcus AF542229.1
Finegoldia AB109771.1
municipal wastewater
treatment plant clone CR933145.1
Oral clone AY134904.1
Peptostreptococcus AF481225.1
Swine manure clone AY167963.1
TCE-dechlorinating clone AY217429.1
Termite gut clone AB088971.1, AB062845.1, AB088954.2, AB088986.1,
AB088970.1
Unclassified
Anaerobic bioreactor clone AJ278169.1
Antarctic sediment clone AY250886.1, AY133397.1, AY177804.1
Arthrobacter X80744.1
Bacillus AF454298.1
Bacteroidetes, uncultured AF449785.1
Beta proteobacterium,
uncultured AY082479
Brackish mud clone,
uncultured AF211303.1
Chicken cecum, uncultured AF376430
Chlorobi clone, uncultured AY118151.1
cow rumen clone AY244902.1, AB185532.1
DCP-dechlorinating clone AJ306793.1, AJ306749.1
Delaware River estuary
clone AY274839.1
80
Desulfotomaculum Y11574.1, Y11573.1, AY084078.1
Feedlot manure clone,
uncultured AF317384.1
Ferribacter AF282254.1, AF282252.1
Forest soil clone, uncultured AY913277.1, AF507760.1
forested wetland clone AF523973.1, AF524015.1
Holophaga AJ519640
hot spring clone AF027097.1
Human mouth clone,
uncultured AF515500.1, AY207065.1
hydrothermal sediment clone AF420340.1, U15103.1
Mono Lake clone AF507859.1, AF507869.2, AF507892.1, AF507879.2
Ocean sediment clone,
uncultured AY181050.1, AY114325.1, AY093473.1
Oral clone AY134895.1
Paralvinella AJ441239.1
Penguin droppings sediment
clone AY218551.1
Plectonema AF091110.1
Rocky Mountain alpine soil
clone AY192273.1, AY192275.1
Salmonella AF029226.1
sludge clone AF234699.1
soil clone AJ390463.1
sponge clone AJ347055.1
temperate estuarine mud
clone AY216458.1
termite gut clone AB089097.1, AB089109.1, AB089074.1, AB089008.1
uranium mining waste pile
clone
AJ519397.1, AJ518784.1, AJ519663.1, AJ519396.1,
AJ532728.1
vent worm enrichment clone AJ431234.1, AJ431235.1
* This entry is included under family Lachnospiraceae in PhyloTrac, and as family
Clostridiaceae in GenBank.
81
CHAPTER 3 HIGH-THROUGHPUT DNA SEQUENCING OF THE
RUMINAL BACTERIA FROM MOOSE (ALCES ALCES) IN VERMONT,
ALASKA, AND NORWAY.
Suzanne L. Ishaq1,*
and André-Denis Wright1,2
*1 Department of Animal Science, College of Agriculture and Life Sciences, University
of Vermont, Burlington, Vermont 05401
2 Department of Medicine, University of Vermont, 111 Colchester Ave., Burlington,
Vermont, 05401
*Contact: Suzanne Ishaq, Department of Animal Science, University of Vermont, 203
Terrill Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-
802-656-8196.
Keywords: 16S rRNA/454 Roche Titanium/Alaska/Norway/rumen/Vermont
Ishaq, S.L. and Wright, A-D.G. (2014). High-throughput DNA sequencing of the
ruminal bacteria from moose (Alces alces) in Vermont, Alaska, and Norway.
Microbial Ecology, 68(2):185-195.
82
3.1 Abstract
In the present study, the rumen bacteria of moose (Alces alces) from three distinct
geographic locations were investigated. Moose are large, browsing ruminants in the deer
family, which subsist on fibrous, woody browse, and aquatic plants. Subspecies exist
which are distinguished by differing body and antler size, and these are somewhat
geographically isolated. Seventeen rumen samples were collected from moose in
Vermont, Alaska and Norway, and bacterial 16S rRNA genes were sequenced using
Roche 454 pyrosequencing with Titanium chemistry. Overall, 109,643 sequences were
generated from the 17 individual samples, revealing 33,622 unique sequences. Members
of the phylum Bacteroidetes were dominant in samples from Alaska and Norway, but
representatives of the phylum Firmicutes were dominant in samples from Vermont.
Within the phylum Bacteroidetes, Prevotellaceae was the dominant family in all three
sample locations, most of which belonged to the genus Prevotella. Within the phylum
Firmicutes, the family Lachnospiraceae was the most prevalent in all three sample
locations. The data set supporting the results of this article is available in the Sequence
Read Archive (SRA), available through NCBI [study accession number SRP022590].
Samples clustered by geographic location and by weight, and were heterogeneous based
on gender, location and weight class (p<0.05). Location was a stronger factor in
determining the core microbiome than either age or weight, but gender did not appear to
be a strong factor. There were no shared operational taxonomic units across all 17
samples, which indicates that these moose may have been isolated long enough to
preclude a core microbiome among moose. Other potential factors discussed include
differences in climate, food quality and availability, gender, and life cycle.
83
3.2 Background
The moose (Alces alces), also known as the Eurasian elk in Europe, is a large
browsing ruminant in the Cervidae (deer) family native to northern latitudes, especially
Canada, the northern United States, Scandinavia and Russia. Their diet typically includes
woody browse from a variety of hardwoods and deciduous species (i.e. willow, aspen,
ash, maple) [1, 2], but during warmer months will also include salt-rich aquatic
vegetation from wetlands and swamps [3]. As a ruminant, they possess a four-chambered
stomach (rumen, reticulum, omasum, and abomasum), of which, the rumen and reticulum
contain a diverse assemblage of microorganisms that break down their fibrous diet and
provide usable nutrients for the host [1, 4].
As many populations of moose are geographically isolated, there are several
recognized subspecies based upon color, structure of the antlers, and facial
features/structure. The present study investigated samples from three different
subspecies of moose in Vermont (VT) (Alces alces americana), Alaska (AK) (Alces alces
gigas), and northern Norway (NO) (Alces alces alces). Alces alces gigas is recognized as
the largest moose subspecies (>600kg for males, >450kg for females), A. alces
americana is mid-range (>450kg for males, >250kg for females), and A. alces alces tends
to be smaller (>250kg for males, >200kg for females). Alces alces alces also have more
distinctive white legs, and have shorter and broader antlers than the other two subspecies.
Generally, moose wean at 6 months, reach sexual maturity at just over 2 years old, and
are known to live up to 15-20 years in the wild [4].
84
Only two published studies currently exist which identify the bacteria present in
the rumen of the moose. The first used traditional culturing techniques to identify the
bacteria in a male moose from Alaska, and identified Streptococcus bovis, Butyrivibrio
fibrisolvens, Lachnospira multiparus, and Selenomonas ruminantium [5]. The second
study used the second generation (G2) PhyloChip to identify hundreds of bacteria from
the rumen and colon of eight moose from Vermont, and reported that the phylum
Firmicutes was dominant, followed by the phylum Proteobacteria [6].
The present study compares three geographic locations of moose using Roche 454
high-throughput sequencing of the 16S rRNA gene using a 500bp amplicon generated
from the universal bacterial primers 27F [7] and 519R [8]. The objectives of this
research were to classify the bacteria present in the rumen of moose from Alaska,
Vermont and Norway; to compare the samples across geographic location, gender, and
weight class to determine possible trends; and to compare samples to published studies
on wild and domesticated ruminants. To date, there has been no study using high-
throughput/next generation sequencing to determine the complexity of the bacterial
community present in the rumen of the moose, nor has there been a comparison of moose
from different geographic locations to determine the core phylotypes which exist in
moose. It was hypothesized that bacterial populations would be distinct based on
geographic location, and that previous studies using classical approaches [5] had
underestimated diversity in the rumen of moose. In previous studies, age [9, 10] and
geographic location [11] play a role in differing core microbiomes.
85
3.3 Methods
3.3.1 Sample Collection
A total of 17 samples (Table 1) were collected from three different geographic
locations over two years. In October 2010, eight whole rumen samples were collected
from moose in Vermont (VT) shot during the 2010 hunting season (October 16-21,
2010). Samples were collected by licensed hunters, during field dressing, within 2h of
death and fixed frozen. Within 24 h, samples were transported to the laboratory and
stored at -20ºC until DNA extraction at the University of Vermont (UVM), Burlington,
VT. Hunters received written and verbal instructions on sample collection to sample
from well inside the rumen and to fill the container to minimize oxygen exposure.
Institutional Animal Care and Use Committee (IACUC) approval was not required to
collect rumen samples from licensed hunters.
Likewise, in the fall of 2011, six samples were collected from licensed hunters in
Norway (NO). The Norwegian moose hunting season is much longer (September 1-
October 31) than that in the United States, thus hunters may be in the field for weeks at a
time. To accommodate this, whole rumen samples were collected during field dressing
and immediately fixed in 70% ethanol until they were brought to the Department of
Arctic Biology, University of Tromsø, Tromsø, Norway. Samples were stored at 4°C
until DNA extraction at the University of Tromsø by the corresponding author. The
DNA extract, containing 0.1 volume of 2M sodium acetate, then two volumes of 100%
ethanol, was shipped to UVM. Once there, samples were centrifuged at 14,000g for 30
min, supernatant was then poured off, and the pellet washed with 100μl of 100% ethanol.
The pellet was air dried and then suspended in 50μl of TE (Tris-EDTA, pH 8.0) buffer.
86
In August, 2012, three whole rumen samples were collected via esophageal tubing
of sedated captive, free-range wild moose at the Moose Research Center, Soldotna,
Alaska (AK) (IACUC protocol #11-021, UVM; ACUC protocol #2011-026, Department
Fish and Game, Alaska). Wild moose there live in an approximately 2 square mile
enclosure where they can forage naturally. Rumen samples were immediately fixed with
70% ethanol and shipped to UVM for DNA extraction. Care was taken to prevent
contamination of rumen digesta sample with saliva. In all samples, approximately 50 g
of whole rumen digesta sample was collected. Previously, it was shown that different
methods of rumen sample collection do not affect the rumen community structure [12].
Vermont samples were collected from October 16-23, 2010 when temperatures
are historically 2-12°C (low/high), however, in 2010 most areas were unusually warm
with daytime highs around 21°C [13]. Norwegian samples were collected between
September 26-October 6, 2011, with temperatures ranging from (low high) 6-13°C in
September, (historically 3-9°C), and 0.8-5°C in October (historically 0-5°C) [13].
Alaskan samples were collected on August 31, 2012, with temperatures ranging from 9-
12°C (historically 5-15°C) [13]. It is important to note that Vermont moose were
sampled during summer-like temperatures, hotter than either Alaskan or Norwegian
moose, despite being sampled at the latest time point in the year. In 2010, Vermont also
received nearly twice the annual average rainfall [14], in 2011, Troms County, Norway
received its highest annual rainfall since 1983 [13]; and in 2012, the region around
Soldotna, Alaska had its highest annual rainfall in six years [13].
87
3.3.2 DNA extraction and quantification
Samples were fully thawed and 0.25 gram aliquots of whole contents (liquid and
particle associated) were used for extraction. DNA was extracted from all 17 samples
individually using he repeated bead-beating plus column (RBB+C) method [14],
combined the QIAamp DNA Stool Mini Kit (QIAGEN, Maryland) and/or the Powersoil
DNA Isolation Kit (MO BIO Laboratories, California). Samples were homogenized
using zirconia beads for 3 min, then incubated with lysis buffer [15] at 70°C for 15 min,
followed by centrifugation at 4°C for 5 min at 16,000G. This was performed twice, and
the supernatant from each was combined and treated with an inhibitex tablet from the
QIAGEN kit. The remainder of the DNA extraction followed the manufacturer’s
instructions. Final elutions were made into 200 μl of TE (Tris-EDTA, pH 8.0) buffer,
and DNA was quantified using a NanoDrop 2000C Spectrophotometer
(ThermoScientific, California). PCR was performed on a C1000 ThermoCycler (Bio-
Rad, California) using the iTaq kit (Bio-Rad, California) to measure the quality of DNA
from the mixed sample of bulk nucleic acids. All PCR results were run on a 1% agarose
gel at 100 volts for 60 min, and imaged on a ChemiDoc XRS+ gel imager (Bio-Rad,
California).
3.3.3 Amplicon library preparation
The variable regions V1-V3 of the bacterial 16S rRNA were recently determined
to be the overall best region to estimate species-level richness using genetic distances of
0.03 and 0.04 for cultured and uncultured bacterial sequences, while providing an optimal
amplicon size of approximately 500b [16]. DNA was PCR amplified with universal
88
bacterial primers (IDT, California): 27F [7], (5’-AGAGTTTGATCCTGGCTCAG -3’)
and 519R [8], (5’-GWATTACCGCGGCKGCTG-3’). These primers were selected to
amplify the first three variable regions (V1-V3) of the 16S rRNA gene in bacteria,
creating an amplicon of ~500bp. The iProof High Fidelity DNA polymerase kit (Bio-Rad,
California) was used: 10µl of 5X High Fidelity buffer which includes MgCl2, 1.0µl of
10mM dNTP mix, 2.5µl each of forward and reverse primer 0.5µl of iProof DNA
polymerase and 31.5µl of ddH2O. For each sample, 2µl of DNA template were added
once the master mix had been aliquoted, to a total reaction volume of 50µl. A PCR
procedure was developed to optimize amplification, as follows: initial denaturing at
98°C for 4 min, then 34 cycles of 98°C for 10 s, 50°C for 30 s, 72° for 2 min, followed
by a final extension step of 72°C for 10 min. All PCR results were run on a 1% agarose
gel, and each sample was run in duplicate or triplicate.
The bands from each moose sample were excised from the agarose gel, combined
per sample, and purified using the QIAGEN QIAQuick Gel Extraction Kit (QIAGEN,
Maryland) according to manufacturer’s instructions. The gel-extracted DNA was re-
eluted into 30µl Buffer EB, and was quantified using a NanoDrop 2000C
Spectrophotometer (ThermoScientific, California) to a minimum required final
concentration of 20ng/µl per 20µl sample. The DNA amplicons were frozen and shipped
overnight to Molecular Research, LP (MR DNA) for Roche 454 pyrosequencing with
Titanium chemistry.
89
3.3.4 Sequencing analysis
Sequences were deposited online in the Sequence Read Archive (SRA) though
NCBI, under study accession number SRP022590. To analyze the DNA sequencing data,
the open-source computer software program MOTHUR ver.1.29 [17, 18] was used.
Sequences from all three locations were processed together using the original standard
flowgram format (sff) output file from the sequencer. Flow grams were denoised using
“shhh.flows”, (i.e. the MOTHUR-integrated version of the PyroNoise algorithm [19]).
The barcode and forward primer were removed, and sequences which contained any of
the following conditions were discarded: < 300 bases, >550 bases, contained
homopolymer runs >8 bases, or contained any mismatches in the barcode. After
trimming, identical sequences were grouped into “unique” sequences using MOTHUR,
which allowed for a comparison of total sequences, as well as those sequences which
were differentiated by at least one base.
Sequences were aligned using the Needleman-Wunsch global alignment
algorithm [20], 8b kmer searching, match reward +1, mismatch penalty -1, and gap
open/extend penalty -2. A reference alignment for bacteria, which had been created and
optimized for this type of data set in the laboratory, was used to align the candidate
sequences. The alignment was then filtered to remove gap-only columns, and sequences
were trimmed to a common length of 392 characters. The alignment was checked for
chimeras using the MOTHUR-integrated version of the program UCHIME [21]; using
abundance as a reference. These putative-chimeric sequences were classified against a
Silva bacterial taxonomy [22, 23], and only those putative-chimeric sequences which had
less than 80% similarity to known sequences were removed from the alignment.
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The remaining aligned sequences were all classified using the Silva reference
taxonomy and an 80% cutoff. Genetic distance was calculated, sequences clustered into
operational taxonomic units (OTUs) at 0.03% and 0.05% genetic distance using the
nearest neighbor method, and a representative sequence chosen for each cluster/OTU at
each distance. Sequences were subsampled from each moose rumen sample, and
diversity was compared using CHAO [24], ACE [25], Good’s Coverage [26] and the
Shannon-Weiner Index [27]. Good’s Coverage, C = 1 - N1/n, where C is the coverage of
a random sample of size n, and N1 is the numbers of “classes” observed once. A large
number of “classes” observed only once will create a value of C approaching 0. Shared
OTUs were generated using the make.shared command in MOTHUR and manual
interpretation of the table. Shared OTUs were also compared using the
get.coremicrobiome command.
A relaxed neighbor-joining tree was calculating using the Clearcut tree making
program within MOTHUR, and then used to run a weighted and unweighted Unifrac
within MOTHUR was run using random sampling. The distance file created from the
weighted Unifrac was used to create a Principal Component Analysis (PCoA) and then
analyzed for population differentiation using an analysis of molecular variance
(AMOVA) test. Unifrac tests were also run online using FastUnifrac [28] to verify
sample structure via clustering, as well as using PCoA plots (viewed in 3D with
Kineimage online), P test significance, and Unifrac significance of all samples.
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3.4 Results
3.4.1 Classification of taxa by sample location
The breakdown of phyla per sample is presented in Figure 1, with the statistical
analysis of the sample populations as follows. The phyla Bacteroidetes, Firmicutes, and
Proteobacteria, and the group “Unclassified” were found in each sample location.
Overall, the phylum Bacteroidetes was dominant in the AK (69.1% of total sequences)
and NO samples (40.4% of total sequences), but not from VT samples (25.7% of total
sequences) (Figure 1). Within the phylum Bacteroidetes, Prevotellaceae was the
dominant family in all three sample locations, with 10,522 unique sequences (33,099
total sequences) across all 17 samples. Within the Prevotellaceae family, 8,526
sequences were identified as belonging to the genus Prevotella: 5,511 sequences from
AK moose (50.4% of unique sequences), 2,625 sequences from NO moose (17.3% of
unique sequences), and 390 sequences (5.2% of unique) from VT. The second largest
group in the phylum Bacteroidetes was the group “RC9” (family Rikenellaceae), with
495 unique sequences (1,827 total sequences) across all samples.
Bacteria belonging to the phylum Firmicutes were dominant in the VT samples
(56.4% of total sequences), were the second most prevalent in NO samples (32.8% of
total sequences), and third most prevalent in AK samples (9.3% of total sequences)
(Figure 1). Lachnospiraceae was the most prevalent family within the phylum Firmicutes
with 6,677 unique sequences (21,252 total) across all samples, followed by
Ruminococcaceae with 1,303 unique sequences (3,018 total). The largest groups at the
genus-level were as follows: Butyrivibrio: 457 unique sequences (1706 total),
Syntrophococcus- 186 unique sequences (514 total), Butyrivibrio-Pseudobutyrivibrio-
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110 unique sequences (402 total), Ruminococcus- 60 unique sequences (155 total),
Mitsuokella- 50 unique sequences (84 total), Moryella- 37 unique sequences (123 total),
Mogibacterium- 30 unique sequences (47 total), and Lachnospira- 24 unique sequences
(64 total).
Uncharacterized and unclassified bacteria at the phylum level represented a large
proportion of sequences: 12.8% unique sequences (18.7% of total) in AK, making it the
second largest group in those samples, 19.5% unique sequences (19.1% of total) in NO
and 14.8% unique sequences (14.7% of total) in VT (Figure 1). Representatives of the
phylum Proteobacteria were the fourth most prevalent bacteria across all 17 samples in
each of the three sample locations. Within this phylum, the most prevalent genera were
Acinetobacter: 173 unique sequences (542 total), and Pseudomonas: 137 unique
sequences (1,247 total). The phyla Cyanobacteria and Actinobacteria were also found in
each sample location, but they were much more prevalent in NO moose (2% and 1% of
sequences, respectively) than in AK or VT moose (<1% and <0.4% of sequences each).
The phyla Lentisphaerae, Spirochaetes, and Synergistetes, as well as the candidate
division “TM7” were found in all three sample locations, with each representing <0.4%
of sequences in any sample location. Fusobacteria was only found in NO samples,
Acidobacteria and Chloroflexi were only found in VT samples, and candidate division
“SR1” was found in NO and VT samples, with <0.4% of sequences in any sample
location.
The following 68 genera were also identified, but with low frequency (i.e. <100
unique sequences): Acetitomaculum, Acetobacter, Acidovorax, Adlercreutzia, Afipia,
Anaerobiospirillum, Anaerococcus, Anaerostipes, Ancalomicrobium, Aquabacterium,
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Atopobium, Barnesiella, Blastomonas, Blautia, Bradyrhizobium, Campylobacter,
Catonella, Caulobacter, Citrobacter, Clostridium, Comamonas, Coprococcus,
Corynebacterium, Desulfovibrio, Duganella, Empedobacter, Eubacterium,
Flavobacterium, Fusobacterium, Howardella, Hydrogenoanaerobacterium, Kurthia,
Lactobacillus, Lactococcus, Leuconostoc, Macrococcus, Massilia, Methylobacterium,
Microbacterium, Mycobacterium, Oerskovia, Olsenella, Oribacterium, Oscillibacter,
Oscillospira, Paenibacillus, Parvimonas, Phascolarctobacterium, Ralstonia, Rhizobium,
Rhodobium, Robinsoniella, Schwartzia, Sediminibacterium, Selenomonas,
Solobacterium, Sphingomonas, Spiroplasma, Stenotrophomonas, Streptococcus,
Succiniclasticum, Succinivibrio, Sutterella, Treponema, Variovorax, Veillonella,
Victivallis, and Xylanibacter.
3.4.2 Statistical analysis of OTUs and clustering
Overall, a total of 109,643 sequences were generated from the 17 samples. Of
these, a total of 37,831 sequences from the three Alaskan samples (AK1R-AK3R)
revealed 10,936 unique sequences, 51,459 total sequences from the six Norwegian
samples (NO1R-NO6R) revealed 15,211 unique sequences, and, 20,353 total sequences
from the eight Vermont samples (VT1R-VT8R) revealed 7,475 unique sequences. The
number of total sequences per sample (Table 1), which passed the quality control and
processing steps, and which were subsequently used in the analysis, ranged from 483 to
19,583. Of the 33,622 unique sequences, 28,111 were classified to phylum (not including
“Unclassified”), 21,122 down to family, and 10,642 down to genus. The unique and total
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number of sequences for each sample location at the family level of classification is
provided (see Supplemental Table 1).
Using a genetic distance of 3%, the 109,662 total sequences were assigned to
17,774 OTUs, of which 15,271 contained a single sequence. Owing to the wide range of
sequences per sample (483 to 19,583), a random subsample of the sequences was
selected, using the smallest sample size as the subsample size, and diversity indices
measured. The CHAO [24] and ACE [25] richness estimators, Good’s [26] coverage,
and Shannon-Weiner [27] diversity index were calculated based a 3% genetic distances
for each sample (Table 2). For the entire dataset, at a 3% genetic distance, and using a
subsample consisting of 483 sequences (i.e. 391 OTUs), the estimated number of OTUs
which should have been observed were CHAO=3,279 and ACE=8,420, Good’s [26]
coverage was 0.261, likely low due to the high proportion of OTU singletons, and
Shannon-Weiner [27] index was 5.726.
No OTUs were shared across all 17 samples, using either get.coremicrobiome or a
shared OTU table (Table 3) at a 3% genetic distance. Overall, only two OTUs were
found at a relative abundance of greater than 1% and were found in at least 10 samples.
No OTUs were present, in any abundance, in 11 or more samples. The Alaskan samples
shared the greatest number of OTUs (n=92), most of which belonged to the genus
Prevotella (Table 3). Among the NO samples (n=6), there were 8 shared OTUs, and
among the VT samples (n=8) there was only 1 shared OTU (Table 3).
When comparing gender, all female samples (n=11) shared 1 OTU, and all male
samples (n=6) shared 6 OTUs (Table 3). When compared by weight, only 12 samples
were taken into account. Five samples were discounted because the three AK samples
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only had estimated live weights, whereas the other 12 samples reported dressed carcass
weight, and samples NO4R and VT4R did not have any recorded weights. The largest
grouping of shared OTUs was seen in the smallest weight class, 0-100kg (NO1R, NO6R),
which shared 67 OTUs, followed by the largest weight class, 301-400kg (VT5R, VT7R,
VT8R) (Table 3). Weight class 101-200kg (NO2R, VT1R, VT3R) shared 26 OTUs
containing 740 unique sequences, and weight class 201-300kg (NO3R, NO5R, VT2R,
VT6R) shared 5 OTUs (Table 3).
Sample clustering was evaluated using weighted and unweighted FastUnifrac
(Figure 2A and B, respectively). For the weighted Unifrac, there was a Unifrac
significance of p=1.0e-03 (corrected), meaning that there is no probability that the branch
lengths would be seen by chance, and a P-Test Significance of p=0.0 (corrected),
meaning that samples were significantly clustered. In both the weighted and unweighted
Unifrac, the three AK samples (AK1R-AK3R) clustered together, and six VT samples
(VT3R-VT8R) clustered together (Figure 2). The remaining two VT samples and the six
NO samples clustered differently between the weighted and unweighted Unifrac. In the
weighted Unifrac, NO1R and NO4R clustered with the large VT clade, while the other
four NO samples clustered separately with VT1R (Figure 2A). Samples NO2R, NO3R,
NO5R, NO6R, and VT1R were all between calf age and approximately 3 years of age. In
the unweighted Unifrac, all six NO samples clustered together, along with VT1R and
VT2R (Figure 2B). The NO moose were all <4 years of age, and VT1R and 2R were 1
year and 3 years old, respectively. However, this is not exclusive, as VT3R and VT6R
were aged 2 years and 3 years, respectively, yet clustered with older and heavier moose.
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In both weighted and unweighted Unifrac, five out of six males clustered together
excluding NO5R, the only male NO moose sample. Additionally, VT6R (female)
clustered with the males both times, and VT2R (female) clustered with males in the
weighted analysis. The five males and two females mentioned above were also the seven
heaviest animals, with the exception of the one male from Norway which clustered with
the five female NO moose samples.
According to PCoA, samples clustered most significantly by geographic location
(Figure 3A), and males clustered significantly, though females did not (Figure 3B).
There was not a strong clustering based on weight class (Figure 3C) or age (data not
shown). According to AMOVA, when comparing diversity across different factors, it
was shown that groups were statistically heterogeneous based on gender (F-
statistic=2.10077, P=0.042), geographic location (Fs=4.63938, P=<0.001), and weight
class (Fs=2.01592, P=0.003).
3.5 Discussion
3.5.1 Bacteroidetes:Firmicutes
Bacteroidetes was the dominant phylum in rumen samples from AK and NO, and
Firmicutes was the dominant phylum in samples from VT, the latter has been previously
demonstrated [6]. Firmicutes was the dominant phylum in Thompson’s gazelle, Grant’s
gazelle, and eland [29]; in Norwegian reindeer [11], and in dromedary camels in
Australia [30]. There are two studies on rumen bacteria from Svalbard reindeer; one
study reporting Bacteroidetes to be dominant in reindeer on a winter diet [31] and the
other reporting Firmicutes to be dominant in reindeer on a late summer diet [11]. This is
97
contrary to a another study using traditional culturing of bacteria from arctic Svalbard
reindeer, which found that Streptococcus bovis (phylum Bacteroidetes) were more
abundant in summer, along with increased starch utilization, proteolysis and lactate
utilization by rumen microbes, whereas fiber digestion, cellulolysis and xylanolysis were
increased during the winter, along with the cellulolytic bacteria Butyrivibrio fibrisolvens
(phylum Firmicutes) [32]. This shift in bacterial phyla dominance reflects the change in
quality and consistency of seasonal diets, as high starch diets and high fiber diets favor
different rumen bacteria.
In the present study, the Lachnospiraceae represented the largest family in the
phylum Firmicutes for all three sample locations, and it was the most abundant family in
the rumen of VT moose. Rumen Lachnospiraceae are a family of bacteria which produce
butyrate, a short-chain fatty acid, which is readily absorbed and metabolized by rumen
epithelial cells [33]. Butyrate reduces the side effects of gastrointestinal inflammation,
and stimulates rumen development by increasing rumen epithelial papillae growth [34].
The prevalence of Lachnospiraceae has been observed previously in studies of the
Tammar wallaby, an Australian herbivorous marsupial [35], dairy cows [36], North
American moose [6], and various arctic ruminants [27]. Furthermore, Lachnospiraceae
was the second-most abundant bacterial family in dromedary camels in Australia [30]. In
the folivorous bird, the Hoatzin, chicks had the highest proportion of Lachnospiraceae,
which decreased as age increased [9]. In the present study, the observed number of
Lachnospiraceae per sample were plotted against age using the statistical package JMP
ver.9.0, and while there appeared to be an inverse relationship between increase in age
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and decrease in the family Lachnospiraceae, the correlation was not significant (R2=0.20)
(data not shown).
Bacteroidetes has previously been shown to be dominant in growing ruminants
[10], or ruminants transitioning from a high-fiber diet to a high-starch/high-digestibility
diet [37], hibernating ground squirrels [38], in the oral cavity of pregnant women [39],
and has been associated with increased fat deposition [40, 41]. Studies involving fecal
transfers from pregnant women to gnotobiotic mice increased the proportion of the phyla
Proteobacteria and Actinobacteria and decreased the proportion of the phyla Firmicutes
and Bacteroidetes, which mirrored the change in women over the course of gestation
[41]. In the present study, only one female moose, NO4R (age and weight unknown),
was confirmed to have a calf, and all other females had an unknown reproductive status.
Proteobacteria was not elevated in this particular sample, but it had the second highest
prevalence of Actinobacteria, after sample NO2R (female, 1.5 year, 120kg dressed
carcass weight).
Previously, it was shown using the G2 PhyloChip microarray that the rumen of
VT moose was largely made up of bacteria in the phylum Firmicutes, followed closely by
bacteria in the phylum Proteobacteria [6]. In the present study, Proteobacteria
represented 4% of total sequences for NO moose, 2.5% of total sequences for AK moose,
and only 1.2% of total sequences for VT moose. This discrepancy is most likely due to
the bias inherent in the G2 PhyloChip, which was created using 16S rRNA
oligonucleotide probes, most of which are designed to target multiple taxa [40], and
which likely produced a large number of false positives [6].
99
3.5.2 Temperature, region, or life stage?
The samples in the present study were collected during unusually rainy seasons in
all three sample locations, and unusually warm seasons in Vermont and Norway [13, 14].
Previously, it has been shown that hot and rainy summers, and not cold summers or
winters, decreased average moose weight in Norway [43]. We speculate that this would
cause plants to mature faster and transition more quickly during the growing season from
a high proportion of starch to a high proportion of structural carbohydrates. Plant starch
is more nutritious, and is likely to be associated with a higher proportion of ruminal
Bacteroidetes, while structural carbohydrates (i.e. cellulose, hemicellulose, lignin), are
very fibrous and are likely be associated with a higher proportion of ruminal Firmicutes
[37, 44]. The unusually mild fall temperatures and heavy rainfall in Vermont may have
increased the cellulose content of forage and, therefore, resulted in a high proportion of
the primarily cellulolytic phylum Firmicutes in the VT moose rumen. This may explain
why the VT moose had a different microbial population than the AK or NO moose.
Moreover, the cooler temperatures in Alaska may have led to a higher starch content in
forage, resulting in moose which had a high proportion of the phylum Bacteroidetes.
AK samples consistently clustered together and shared the greatest number of
OTUs and unique sequences. This is unsurprising, as these moose cohabited the same 2
square mile enclosure for years, were likely consuming a similar diet, and were roughly
the same age. However, the VT and NO samples each clustered separately with a large
amount of consistency, which was not observed among age or weight groups across all
sample locations. This suggests that geographic location and, thus, available forage,
plays a large role in defining the core microbiome in the three isolated populations in the
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present study [11]. Age/life stage may play a larger role in defining the core microbiome
within a sample location and account for individual variation [6, 9, 41]. While males did
cluster on PCoA graphs and Unifrac, and shared six OTUs, this was not seen in females,
potentially due to their different reproductive stages. Although there was significant
clustering of females based on weight/age using Unifrac, it was not corroborated using
PCoA, and they shared only one OTU. This discrepancy could be due to the low number
of samples per age/weight group.
3.6 Conclusion
The present study found that samples taken from Vermont (USA), Alaska (USA),
and Norway differ from each other in terms of phylogenetic diversity with respect to
geographical location, gender, and weight of the host animal. The observed clustering
trends, between moose populations, are likely due to different quality of diet between
populations, which may be due to differing location, climate, and sampling season
between the three groups.
3.7 Availability of Supporting Data
The data set supporting the results of this article is available in the Sequence Read
Archive (SRA), available through NCBI [study accession number SRP022590].
3.8 Competing Interests
The authors declare no competing interests.
101
3.9 Authors’ Contributions
SLI performed all laboratory procedures, excluding Roche 454 pyrosequencing, analyzed
the dataset, and wrote the manuscript. ADW conceived of the project, facilitated
Norwegian sample collection, funded all work and edited the manuscript.
3.10 Acknowledgments
The authors would like to acknowledge: the Vermont Fish and Wildlife Dept. for
sample collection logistics; Terry Clifford, Archie Foster, Lenny Gerardi, Ralph Loomis,
Beth and John Mayer, and Rob Whitcomb for collection of Vermont moose samples; Dr.
Even Jørgensen, University of Tromsø, and Dr. Helge K. Johnsen, University of Tromsø,
for collection of Norwegian moose samples; Dr. Monica A. Sunset, University of
Tromsø, for facilitating sample collection and storage, as well as for providing DNA
extraction materials for the Norwegian samples; Dr. John Crouse and Dr. Kimberlee
Beckmen, both of the Alaska Dept. of Fish & Game for collection of Alaskan moose
samples; and Dr. Benoit St-Pierre, University of Vermont for assistance with MOTHUR
and Perl programming.
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3.12 Figures
Figure 3-1 A comparison of sequences per sample, using the Silva bacterial reference taxonomy for
classification.
Alaska (AK): 37,831 total; Norway (NO): 51,459 total; Vermont (VT): 20,353 total; overall: 109,643 total.
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Figure 3-2 FastUnifrac clustering of all 17 samples. A) weighted, non-normalized, and B)
unweighted.
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Figure 3-3 PCoA graphs colored by variable.
A) geographic location: red=AK, blue=NO, yellow=VT, B) gender: red=female, blue=male, C) weight
class: pink=not available, red=0-100 kg, light blue=101-200kg, yellow=201-300 kg, green=301-400 kg,
and purple=400+ kg for live weights.
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3.13 Tables
Table 3-1 Metadata of the 17 samples from Alaska (AK), Norway (NO), and Vermont (VT).
Sample Sample Site Collection
m-d-y Sex
Weight
(kg)1
Approx
. age2
# Seqs used
for analysis3
AK-1R Soldotna, AK
60°29′N 151°4′W 08-31-12 F
485 (live
wt.)
10y
3mo 5,695
AK-2R “ ” 08-31-12 F 487 (live
wt.)
10y
3mo 12,550
AK-3R “ ” 08-31-12 F 506 (live
wt.)
11y
3mo 19,586
NO-1R Troms County, NO
69°N 20°E 09-26-11 F
61
(dressed) Calf 6,028
NO-2R “ ” 09-26-11 F 120
(dressed) 1.5y 18,543
NO-3R “ ” 09-26-11 F 211
(dressed) >4.5y 3,122
NO-4R “ ” 09-30-11 F N/A N/A4 3,037
NO-5R “ ” 09-27-11 M 290
(dressed) 2-3y 17,624
NO-6R Andørja, Ibestad, NO
68°N 17°E 10-08-11 F
77
(dressed)
Calf,
6-8 mo. 3,105
VT-1R Averill, VT
44°59'N, 71°42'W 10-16-10 F
185
(dressed) 1y 3,484
VT-2R East Haven, VT
44°39’N, 71°53’W 10-16-10 F
244.6
(dressed) 3y 1,744
VT-3R North Danville, VT
44°27’N, 72°5’W 10-17-10 M
186.4
(dressed) 2y 3,405
VT-4R Canaan, VT
44°59’N, 71°32’W 10-16-10 M N/A N/A 3,679
VT-5R Ferdinand, VT
44°42.7’N, 71°45.19’W 10-20-10 M
319.1
(dressed) 4y 3,261
VT-6R Brighton, VT
44°48.3’ N, 71°51.3’W 10-23-10 F
259.6
(dressed) 3y 483
VT-7R Walden, VT
44°26.3’N, 72°13.4’W 10-23-10 M
301.3
(dressed) 4y 2,305
VT-8R Wheelock, VT
44°35.28’N, 72°5.33’W 10-23-10 M
405.5
(dressed) 8y 1,992
1AK moose were weighed live, VT and NO moose carcasses were field dressed and
weighed at reporting stations. 2 AK moose had birthdates, VT and NO moose age was
estimated using wear on teeth. 3 Unique sequences = 33,622
4Moose had a bull calf.
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Table 3-2 Statistical measures using a subset of sequences per sample.
Sample # OTUs in
sample CHAO ACE
Good’s
Coverage
Shannon-Weiner
Index
AK_1R 962 6,012 11,389 0.576 5.700
AK_2R 1,707 9,846 22,158 0.554 6.523
AK_3R 2,374 15,861 45,718 0.642 5.787
NO_1R 1,329 7,737 20,686 0.381 6.813
NO_2R 2,926 18,244 42,501 0.538 7.047
NO_3R 563 3,253 3,792 0.380 5.779
NO_4R 730 4,459 10,654 0.327 6.364
NO_5R 3,554 25,415 62,870 0.409 7.654
NO_6R 774 6,318 18,613 0.273 6.433
VT_1R 987 6,630 15,544 0.279 6.690
VT_2R 539 3,179 3,393 0.268 6.149
VT_3R 992 6,230 15,364 0.282 6.765
VT_4R 1,106 7,430 12,943 0.294 6.77
VT_5R 958 5,776 14,374 0.307 6.649
VT_6R 148 2,122 3,450 0.113 4.957
VT_7R 669 4,407 8,443 0.303 6.335
VT_8R 686 5,607 5,544 0.185 6.471
Table 3-3 The number of shared OTUs across different samples at a 3% genetic distance generated
using a shared OTU table in MOTHUR.
Samples Compared OTUs Shared,
3% distance
Shared Unique
Sequences
AK samples (n=3) 92 4,510
NO samples (n=6) 8 380
VT samples (n=8) 1 136
All 17 samples 0 0
All Females (n=11) 1 114
All Males (n=6) 6 314
Weight: 0-100 kg (NO1R, NO6R) 67 433
Weight: 101-200 kg (NO2R, VT1R, VT3R) 26 740
Weight: 201-300 kg (NO3R, NO5R, VT2R, VT6R) 5 417
Weight: 301-400 kg (VT5R, VT7R, VT8R) 28 276
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CHAPTER 4 DESIGN AND VALIDATION OF FOUR NEW PRIMERS FOR
NEXT-GENERATION SEQUENCING TO TARGET THE 18S RRNA GENE
OF GASTROINTESTINAL CILIATE PROTOZOA.
Suzanne L. Ishaq and André-Denis G. Wright
Department of Animal Science, College of Agriculture and Life Sciences, University of
Vermont, 570 Main St., Burlington, Vermont 05401
Contact: Suzanne Ishaq, Department of Animal Science, University of Vermont, 203
Terrill Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-802-
656-8196.
Keywords: Alaska/Entodiniomorphida/ciliophora/moose/protist/rumen/Vestibuliferida
Ishaq, S.L. and Wright, A-D.G.. (2014). Design and validation of four new primers for
next-generation sequencing to target the 18S rRNA gene of gastrointestinal ciliate
protozoa. Applied and Environmental Microbiology, 80(17): ahead of print.
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4.1 Abstract
Four new primers and one published primer were used to PCR amplify hyper-
variable regions within the protozoal 18S rRNA gene to determine which primer pair
provided the best identification and statistical analysis. PCR amplicons of 394 to 498
bases were generated from three primer sets, sequenced using Roche 454 pyrosequencing
with Titanium, and analyzed using the BLAST (NCBI) database and MOTHUR ver.
1.29. The protozoal diversity of rumen contents from moose in Alaska was assessed. In
the present study, primer set 1, P-SSU-316F + GIC758R (amplicon = 482 bases) gave the
best representation of diversity using BLAST classification, and amplified Entodinium
simplex and Ostracodinium spp., which were not amplified by the other two primer sets.
Primer set 2, GIC1080F + GIC1578R (amplicon = 498 bases), had similar BLAST results
and a slightly higher percentage of sequences that identified with a higher sequence
identity. Primer sets 1 and 2 are recommended for use in ruminants. However, primer set
1 may be inadequate to determine protozoal diversity in non-ruminants. Amplicons
created by primer set 1 were indistinguishable for certain species within the genera
Bandia, Blepharocorys, Polycosta, Tetratoxum, or between Hemiprorodon
gymnoprosthium and Prorodonopsis coli, none of which are normally found in the
rumen.
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4.2 Introduction
Rumen ciliate protozoa represent important functional members of the rumen
environment, as most have some cellulolytic or amylolytic abilities (1–3). Most studies
of rumen ciliate protozoa are performed using microscopy and traditional culturing
techniques (2, 4–10), quantitative PCR (11, 12), denaturing gradient gel electrophoresis
(13), and full-length 18S rRNA clone libraries (13, 14). A few studies of rumen ciliate
protozoa use high-throughput sequencing, although primer selection remains a problem,
as some studies use universal eukaryotic primers, primers which target only one ciliate
protozoa signature region, or primers which produce unsuitable long amplicons for
current high-throughput technology (15–20).
The 18S rRNA gene ranges from 1.5 kb to over 4.5 kb (21), and in rumen ciliate
protozoa it is generally 1.5 kb to 1.8 kb in length. Like the 16S rRNA gene of
prokaryotes, the 18S rRNA gene of eukaryotes has nine hyper-variable regions (V1–V9)
which can be used for genus/species identification. Four gut ciliate signature regions
exist within the rumen protozoal 18S rRNA gene, which represent areas of high
variability that can improve identification down to species level (22,23). Signature
region 1 occurs between 440–460bp (within V3), signature region 2 occurs between 590-
620bp (between V3 and V4), signature region 3 occurs between 1220–1260bp (within
V6), and signature region 4 occurs between 1560–1580bp (after V8) (Figure 1).
Additionally, rumen ciliate protozoa have a slightly different 18S rRNA secondary
structure from non-rumen ciliates, in that rumen protozoa are missing helix E23–5 from
the V4 region and other helices in the region are shorter (21-23). Previously, the V9
region (15) or the V5–V7 regions (13) have been amplified for phylogenetic analysis
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using high-throughput techniques. Ciliated protozoa found in the gastrointestinal tract of
animals belong to the phylum Ciliophora, class Litostomatea, subclass Trichostomatia,
and the orders Entodiniomorphia and Vestibuliferida. The vast majority of rumen
ciliated protozoa belong to the Ophryoscolecidae, the largest family (both in numbers of
species and genera) within the Entodiniomorphia.
In the present study, four new primers were designed to specifically target
conserved 18S rRNA gene regions for ciliate protozoa, which are normally found in the
gastrointestinal tract of herbivores. Using our protocol, these primers did not amplify
other eukaryotic, bacterial, or archaeal species, or non-ciliated protozoa which are not
normally found in a healthy gastrointestinal tract environment. The strategy for the
pairing of the forward and reverse primers was to create amplicons which included at
least one of the four signature regions of the rumen ciliate protozoal 18S rRNA gene.
Current limitations of the Roche 454 and MiSeq ver. 3.0 (with 2 x 300 base paired ends)
platforms, along with few reliable conserved regions, exclusive to ciliate protozoa,
prevent the inclusion of all four signature regions, which was possible when the full 18S
rRNA gene was sequenced using Sanger sequencing technology.
The first objective of the present study were to test these primer pairs on rumen
samples from the North American moose (Alces alces) to determine their suitability and
validity for rumen ciliate identification. The second objective was to compare the primer
sets using CHAO, ACE, Shannon-Weaver, Inverse Simpson, Good’s Coverage, and
Unifrac in order to make a recommendation of the most suitable primer set for rumen
protozoal 18S rRNA gene amplification.
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4.3 Materials and Methods
4.3.1 Sample collection and DNA extraction
On August 31, 2012, whole rumen samples were collected via esophageal tubing
of three captive, free-range wild moose at the Moose Research Center, Soldotna, Alaska
(AK) (IACUC protocol #11-021, University of Vermont; ACUC protocol #2011-026,
Department Fish and Game, Alaska). All three moose were females between 10-11 years
of age. Rumen samples were mixed with 70% ethanol and shipped to the University of
Vermont (Burlington, Vermont, USA) where they were stored at 4°C. To confirm the
sequencing results, all three moose samples were visual inspected using light microscopy
to identify genera of rumen ciliates.
To extract DNA, a 5 ml aliquot of whole rumen contents in ethanol was
centrifuged for 5 min at 16,000 x G, and ethanol was removed by pouring off the liquid
fraction. From the remaining whole contents of all the samples, 0.25 g aliquots of whole
contents (liquid and particle associated) were used for extraction. DNA was extracted
from the three rumen samples using the repeated bead-beating plus column (RBB+C)
method (24), combined with the QIAamp DNA Stool Mini Kit (QIAGEN, Maryland).
The final elutions were made using 200 μl of TE buffer (1M Tris-HCL, 0.5M EDTA, pH
8.0), and eluted DNA was quantified using a NanoDrop 2000C Spectrophotometer
(ThermoScientific, California).
4.3.2 Primer design
The new forward and reverse primers were designed to target signature regions
unique to gastrointestinal tract ciliate protozoa within the 18S rRNA gene. Protozoal 18S
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rRNA gene reference alignments were created and used to select areas, which were
highly conserved among the rumen ciliate protozoa. Four conserved regions were
selected, and a potential primer sequence identified from each of those regions. The four
new primers were given the prefix “GIC” for gastrointestinal ciliates, and are as shown in
Table 1 with specifications. Along with a previously described rumen protozoal primer,
P-SSU-316F (5’-GCTTTCGWTGGTAGTGTATT-3’) (12), primer sequences were
compared to known sequences of gastrointestinal ciliates in GenBank (NCBI) (Table 2)
to determine specificity to amplify only gastrointestinal tract ciliate protozoa.
Primer set 1, P-SSU-316F (12) and GIC758R, created an amplicon of 482 bases
(primers not included) which encompassed variable regions V3-V4, and rumen ciliate
signature regions 1-2 (Figure 1). Primer set 2, GIC1080F and GIC1578R, created an
amplicon of 498b, which encompassed V6-V8 and signature regions 3-4 (Figure 1).
Primer set 3, GIC1184F and GIC1578R, created an amplicon of 394b, which also
encompassed V6-V8, and rumen ciliate signature regions 3-4 (Figure 1).
4.3.3 PCR amplification
The Phusion High-Fidelity DNA polymerase kit (ThermoScientific,
Massachusetts) was used for PCR: 10 µl of 5X High Fidelity buffer (including MgCl2),
1.0 µl of 10 mM dNTP mix, 2.5 µl each of forward and reverse primer at 10 mM
concentration, 0.5 µl of Phusion DNA polymerase (2U/μl), and 31.5 µl of ddH2O. DNA
templates (2 µL of 10-50ng/µL concentration) were added once the master mix had been
aliquoted, to a total reaction volume of 50 µl. The PCR protocol was adapted from
previous literature (12); 94°C for 4 min hot start, followed by 30 cycles of 94°C for 30 s,
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55°C for 30 s, and 72°C for 1 min, with a final extension of 72°C for 6 min on the last
cycle. All PCR results were run on a 1% agarose gel at 100 volts for 60 min, and imaged
on a ChemiDoc XRS+ gel imager (Bio-Rad, California).
DNA bands of the correct amplicon size were excised out of the agarose gel for
DNA purification, using the QIAQuick Gel Extraction Kit (QIAGEN, Maryland)
according to the manufacturer’s instructions. For each primer set, all gel bands from each
of the three moose samples were filtered through the same column. The gel–extracted
DNA from each primer set was quantified using a NanoDrop 2000C Spectrophotometer
(ThermoScientific, California), at a minimum final concentration of 20 ng/µl, at a volume
of 20 µl. The DNA amplicons from the three test primer sets were frozen and shipped
overnight to Molecular Research DNA (MR DNA), Shallowater, Texas, USA, for Roche
454 pyrosequencing with Titanium chemistry.
4.3.4 Sequence analysis
Sequences were deposited online in the Sequence Read Archive (SRA) though
NCBI, under study accession number SRP034591. To analyze the DNA sequencing data,
the open-source computer software program MOTHUR ver.1.29 (25) was used.
Sequences from all three primer sets were processed independently using the original
standard flowgram format (sff) output file from the sequencer. Flow grams were
denoised using the MOTHUR-integrated version of the PyroNoise algorithm (26), which
also creates phylotypes, which is a unique sequence representing multiple identical
sequences. Unique sequences are not equivalent to singletons, which are operational
taxonomic units (OTUs) containing a single sequence. The barcode and primer
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sequences were removed, and sequences which contained any of the following conditions
were discarded: <400 bases for primer set 1 and 2 or <375 bases for primer set 3, >500
bases, homopolymer runs >8 bases, or any mismatches in the barcode.
To determine the genetic distance cutoffs for species-level comparisons, 51 full-
length 18S rRNA valid protozoal reference sequences were obtained from NCBI (Table
2, Supplemental Figure 4). These reference sequences were then trimmed using the three
test primer sets as trim points. BLAST sequences were manually aligned and pairwise
distances were calculated using PHYLIP (ver. 3.69) using a Kimura 2-parameter model
(Table 3). A total of 51 pairwise species (within genus) and 2,926 pairwise distances
between genera were compared using validly recognized species to determine genetic
distances.
Sequences were aligned using the Needleman-Wunsch global alignment
algorithm (27), 8 base kmer searching, match reward +1, mismatch penalty -1, and gap
open/extend penalty -2. An 18S rRNA gene reference alignment, featuring rumen and
non-rumen ciliate protozoal sequences downloaded from NCBI, was created in the
laboratory to provide a better alignment of candidate sequences. The reference alignment
contained 219 full-length 18S rRNA sequences for all available gastrointestinal tract
(rumen, forestomach, cecum, and colon) ciliates sequences, as well as non-ruminant
ciliates and non-ciliate protozoal sequences from BLAST. The reference alignment
contained all 51 sequences previously used to determine genetic distance cutoffs. The
candidate alignment was then filtered to remove gap-only columns, and any sequences
which would not align (<10 sequences per data set). The candidate alignment was
checked for chimeras using the MOTHUR-integrated version of the program UCHIME
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(28); using the ciliate 18S rRNA gene sequence reference alignment which was created in
our laboratory. To determine the specificity of the primers, unique sequences were
classified using BLAST.
Sequences from the three primer sets were trimmed to a uniform length per
library (Table 3), and clustered using the Nearest Neighbor method to determine
observed number of OTUs per library. Libraries were then subsampled equal to the
smallest library (n=424 sequences per library), and Shannon-Weaver Diversity index
(29), Good’s Coverage (30), Inverse Simpson (31), CHAO (32), and ACE (33) were
calculated for each library based on the recommended genetic distance. Like Simpson’s
Diversity, Inverse Simpson measures number and abundance of species. However, it
weights rare species lower than Simpson to prevent a dramatic increase in diversity with
the addition of rare species. Additionally, using MOTHUR, relaxed neighbor-joining
trees were created from trimmed sequences (375 bases) using CLEARCUT, and trees
were clustered using weighted and unweighted Unifrac as a measure of similarity of
abundance and structure between libraries.
4.4 Results
4.4.1 Primer set 1: P-SSU-316F + GIC758R
A total of 12,326 sequences passed quality assurance measures and were used for
sequence analysis. Of these, 769 sequences were unique (Table 3). Using aligned
sequences of valid protozoa to generate pairwise genetic distances (see Supplemental
Figure 1), the species and genus-level cutoffs were determined to be 0.036 and 0.087,
respectively. So, a 4% species-level cutoff and a 9% genus-level cutoff were comparable
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to cutoffs for near full-length gene sequences. Sequences were trimmed to 450 bases, and
various diversity indices calculated for the data set. At a 4% species-level cutoff, 48
species-level OTUs were observed, and at 9% genus-level cutoff, 15 genus-level OTUs
were observed (Table 3). ACE, CHAO, Shannon-Weaver and Inverse Simpson values
can be found in Table 3.
Using BLAST, the most prevalent taxon was Polyplastron multivesiculatum,
which represented nearly 60% of the unique sequences, followed by the genus
Entodinium, which represented just over 20% of unique sequences (Figure 2). The most
prevalent species of Entodinium were Ent. furca dilobum (7% of unique sequences) and
Ent. nanellum (5% of unique sequences). Epidinium caudatum represented 5% of unique
sequences (Figure 2). Primer set 1 amplified Ent. simplex, Ostracodinium gracile, and
other Ostracodinium spp., which were not amplified by other primer sets. The percent
identity to known sequences ranged from 95-100% for primer set 1, with 66% of
sequences having a 99% identity to a known sequence in BLAST (Figure 3). However,
there were six sequences that had a 99-100% identity on only 93-95% of the query
sequence. The average percent identity to Ostracodinium gracile was 98.2% (range 97-
99%). There were 21 unique (63 total) sequences, which had <96% identity to a known
sequence.
During the calculation of genetic distances using pairwise comparisons, it was
noted that the amplicon created by primer set 1 could not differentiate between
Blepharocorys microcorys (AB794975) and Blepharocorys uncinata (AB530162),
between Hemiprorodon gymnoprosthium (AB795028) and Prorodonopsis coli
(AB795029), between Tetratoxum excavatum (AB794971) and Tetratoxum parvum
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(AB794969), between Bandia deveneyi (AY380823) and Bandia smalesae (AF298822),
and between Polycosta roundi (AF298819) and Polycosta turniae (AF298818).
4.4.2 Primer set 2: GIC1080F + GIC1578R
A total of 6,070 sequences for this primer set passed quality assurance measures
and were used for sequence analysis. Of these, 697 sequences were unique (Table 3).
Using aligned sequences of valid protozoa to generate pairwise genetic distances (see
Supplemental Figure 2), the species and genus-level cutoffs were determined to be 0.039
and 0.079, respectively. For statistical analysis, sequences were trimmed to a uniform
length of 450 bases. At a 4% species-level genetic distance cutoff, 25 species-level
OTUs were observed, and at 8% genus-level cutoff, 14 genus-level OTUs were observed
(Table 3). ACE, CHAO, Shannon-Weaver and Inverse Simpson values can be found in
Table 3.
Sequences from this primer set represented over 60% Polyplastron
multivesiculatum (Figure 2). The next predominant genus was Entodinium with 30% of
unique sequences and, of that, Ent. nanellum represented approximately two-thirds of the
genus (20% of unique sequences) (Figure 2). Diploplastron affine and Epidinium
caudatum were the third most prevalent taxa, with 5% of unique sequences each. The
percent identity to known sequences ranged from 94-100% for primer set 2, with 67% of
sequences having a 99% identity to a known sequence in BLAST (Figure 3). Only 1
unique (9 total) sequence had <96% identity to known sequences.
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4.4.3 Primer set 3: GIC1184F + GIC1578R
A total of 8,265 total sequences passed quality assurance measures and were used
for sequence analysis. Of these, 424 sequences were unique and used for BLAST (Table
3). Using aligned sequences of valid protozoal to generate pairwise genetic distances
(see Supplemental Figure 3), the species and genus-level cutoffs were determined to be
0.042 and 0.096, respectively. For statistical analysis, sequences were trimmed to a
uniform length of 375 bases. At a 4% species-level genetic distance cutoff, 20 species-
level OTUs were observed, and at 10% genus-level cutoff, 12 genus-level OTUs were
observed (Table 3). ACE, CHAO, Shannon-Weaver and Inverse Simpson values can be
found in Table 3.
Over 75% of unique sequences in the primer set 3 dataset were classified as
Polyplastron multivesiculatum using BLAST (Figure 2). The next predominant genus
was Entodinium, representing approximately 15% of the unique sequences (Figure 2).
Epidinium was the third most prevalent genus, with <5% of the unique sequences. The
percent identity to known sequences ranged from 95-99% for primer set 3, with 76% of
sequences having a 98% identity to a known sequence in GenBank (Figure 3). There
were 2 unique sequences, which had <96% identity to a publically available sequence.
4.4.4 Comparison of the three primer sets
Primer set 1 (P-SSU-316F + GIC758R) had the highest number of observed
OTUs, as well as the highest ACE, CHAO, Shannon-Weaver and Inverse Simpson values
of all three primer sets, indicating the highest amount of diversity of the three amplicon
libraries (Table 3). Primer set 1 had the lowest Good’s coverage (0.95). Primer set 2
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(GIC1080F + GIC1578R) had the second largest number of observed OTUs, and second
largest CHAO. However, primer set 2 had the lowest ACE, Shannon-Weaver, and
Inverse Simpson values, indicating a low amount of diversity (Table 3). Primer set 3 had
the lowest number of observed OTUs, as well as the lowest CHAO estimate (Table 3).
However, primer set 3 had the second highest ACE, Shannon-Weaver, and Inverse
Simpson values (Table 3). Weighted and unweighted Unifrac analyses were also run
using MOTHUR. Primer sets were not significantly different based on weighted (0.96 –
1.0), or unweighted (0.98 – 1.0, p<0.001) Unifrac. There was no correlation between
sequence length and % identity to known sequences in BLAST for any of the three data
sets.
Genera of rumen ciliates were confirmed using light microscopy. Various species
of Entodinium, as well as Polyplastron multivesiculatum and Epidinium cattanei were
found in abundance in all three samples. Isotricha were found in two samples, and
Ostracodinium was found in one sample.
4.5 Discussion
This study validated three primer sets for the amplification of gastrointestinal tract
ciliate protozoa for use in high-throughput sequencing, as well as determined the
diversity of moose rumen protozoa from Alaska, USA. All three test primer sets were
able to amplify 18S rRNA protozoal sequences. The 18S rRNA gene is highly conserved
among eukaryotes, and finding potential primer sites, which are specific to certain taxa
can be challenging. Using the new primers reported in the present study, under the same
amplification parameters (i.e. PCR annealing temperature, removal of short amplicons),
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only 18S rRNA genes from gastrointestinal tract (rumen, forestomach, cecum and colon)
ciliate protozoa should be targeted for amplification.
Previously used primers for high-throughput sequencing were often universal
eukaryotic primers (15-19), or primers which targeted only one signature region for the
ciliate protozoa (18, 20). In several studies, this resulted in sequences which were not
ciliate or protozoan in nature (17, 19), or which were too short (<200 bases), thereby
increasing the risk for misidentification (18) given the overall high degree of
conservation of the 18S gene across eukaryotic taxa. In the present study, no non-
protozoal eukaryotic sequences (i.e. plant, fungal or host DNA) were amplified.
Previously, using classical microbiology, Dehority (6) identified just five species
of protozoa from the rumen of Alaskan moose, Sládeček (4) identified four species from
moose, and Westerling (34) identified just two species from moose in Finland. In the
present study, 12 species representing 7 genera were found across the three Alaskan
moose. Previously, between 16 to 24 rumen ciliate species, represented by 1 to 9 genera,
were found in in studies of wild reindeer (9, 35–39), wild musk ox (Ovibos moschatus)
(6), wildebeest (Connochaetes spp.) (40), Kafue lechwe antelope (Kobus leche kafuensis)
(41), Sassaby antelope (Damaliscus lunatus) (10), and tsessebe (Damaliscus lunatus
lunatus) (42).
Only one study exists, which investigated the rumen protozoa from three bull-
moose in Alaska, USA, using culturing and microscopy techniques (6). Previously,
Entodinium alces and Entodinium exiguum were reported to be the two dominant species
in moose rumen contents, whereas Entodinium dubardi, Entodinium simplex, and
Entodinium longinucleatum were present in one moose (6). Additionally, Entodinium
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dubardi and Epidinium caudatum were identified in moose rumen samples from Finnish
Lapland (34), and Entodinium dubardi, Entodinium simplex, Ostracodinium obtusum,
and Epidinium ecaudatum were isolated from moose in Slovakia (4). Eudiplodinium
neglectum was also first identified in a moose from Canada (5).
Based on the previous studies which identified the rumen ciliate protozoa in the
moose, it was surprising that Polyplastron are the dominant species in the present study.
Polyplastron produce xylanases, carboxymethylcellulases, and various other
endoglucanases, which digest fiber in the rumen. While the presence of Polyplastron
was validated using light microscopy in the present study, a large number of sequences
related to Polyplastron may be explained by rRNA copy numbers in ciliates, which could
be highly variable from one species to another. Also, there is a lack of publically
available sequences for the rumen ciliates, especially closely related genera to
Polyplastron, such as Elytroplastron and Eudiplodinium. This is also true of Entodinium
alces, Entodinium exiguum, Ostracodinium obtusum, Epidinium ecaudatum, and
Eudiplodinium neglectum, all of which were previously found in moose (4–6), but no
representative sequences exist for these species. This makes identification at a species
level very difficult until additional sequences from all described species are elucidated.
There were 74 total sequences (24 unique sequences), which had <96% identity to
publically available sequences. Given that the genetic distance between Epidinium
caudatum and Epidinium ecaudatum is 1.3%, some sequences in the present analysis with
genetic distances between 1.0-1.5% to Epi. caudatum may represent other species of
Epidinium, such as Epidinium cattanei, which was observed under light microscopy.
Similarly, given that Polyplastron multivesiculatum has 98% sequence identity to
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Ostracodinium gracile and Ostracodinium clipoleum, the large number of sequences
which have <98% identity to P. multivesiculatum, may in fact represent other closely
related species or genera. As we stated previously, more representative sequences from
other rumen ciliates, such as Epi. cattanei, are needed to confirm these interpretations of
the data.
Based on the analysis in the present study, the primer set which gave the best
representation of diversity using BLAST was primer set 1, P-SSU-316F + GIC758R.
Primer set 1 amplified Entodinium simplex and Ostracodinium spp., which were not
amplified by either of the other two primer sets. However, primer set 2 had a slightly
higher percentage of sequences classified at a higher % identity in BLAST than primer
set 1. Both primer sets produced an amplicon of greater than 400 bases. Primer set 1 (P-
SSU-316F + GIC758R) had the highest number of observed OTUs, as well as the highest
ACE, CHAO, Shannon-Weaver and Inverse Simpson values of all three primer sets,
indicating the highest amount of diversity of the three amplicon libraries. Primer set 3
had the second highest ACE, Shannon-Weaver, and Inverse Simpson values. While
primer sets 2 and 3 target the same variable and signature regions, primer set 2 spans a
larger area of conserved region, which may account for the lower estimated diversity than
primer set 3.
It is important to note that primer set 1 (P-SSU-316F + GIC758R) produced
amplicons which could not differentiate between the pairs Blepharocorys microcorys and
Blepharocorys uncinata, Hemiprorodon gymnoprosthium and Prorodonopsis coli,
Tetratoxum excavatum and Tetratoxum parvum, Bandia deveneyi and Bandia smalesae,
and Polycosta roundi and Polycosta turniae. The aforementioned Blepharocorys spp.
127
(43), Hemiprorodon gymnoprosthium (44), Prorodonopsis coli (45), and Tetratoxum
spp. (46) have previously been found in the hind gut of the horse, and Bandia deveneyi,
B. smalesae, Polycosta roundi, and P. turniae in Australian marsupials (47). Since these
ciliate species mainly occur in non-ruminants, either P-SSU-316F + GIC758R or
GIC1080F + GIC1578R could be used in ruminants, but only GIC1080F + GIC1578R
should be used in non-ruminants. However, in order to bring about standardization of the
amplification of rumen ciliates and to better enable comparison across studies, GIC1080F
+ GIC1578R seems to be the better choice for a general gut ciliate primer set.
4.6 Acknowledgements
The authors would like to acknowledge Dr. John Crouse and Dr. Kimberlee Beckmen of
the Alaskan Department of Fish and Game for their assistance in rumen sample
collection.
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4.8 Figures
Figure 4-1 A map of the full-length protozoal 18S rRNA gene, including variable (V1-V9) and rumen
ciliate signature regions (SR1-SR4), and showing the respective amplicons of the three primer sets
used in the present study.
133
Figure 4-2 Taxonomy and proportion of unique pyrosequences using NCBI (BLAST), by forward
primers P-SSU-316F (Sylvester et al., 2004), GIC1080F (present study), and GIC1184F (present
study).
All sequences used passed all quality assurance steps outlined in Methods.
134
Figure 4-3 Distribution of sequence identity percentages to known sequences based on BLAST by
sequencing primer.
135
4.9 Tables
Table 4-1 Gastrointestinal tract ciliate protozoal primer specifications.
Primer
Name Sequence (5’3’)
Tm*
(50mM
NaCl)
Dimer
Formation
Hairpin
Formation
End
Stability
GIC758R CAACTGTCTCTATKAAYCG 47.4°C 2 bp 2 bp Medium
GIC1080F GGGRAACTTACCAGGTCC 53.6°C 3 bp 3 bp Medium
GIC1184F TGTCTGGTTAATTCCGA 47.2°C 4 bp 3 bp High
GIC1578R GTGATRWGRTTTACTTRT 42.1°C 2 bp 2 bp High
*Melting temperature. K=G/T Y=C/T R=A/G W=A/T
136
Table 4-2 18S rRNA protozoal reference sequences used to determine genetic distance cutoff.
Species Accession
#
Species Accession
#
Alloiozona trizona AB795026 Epidinium ecaudatum AM158465
Amylovorax dehorityi AF298817 Eremoplastron dilobum AM158472
Amylovorax dogieli AF298825 Eremoplastron neglectum AM158473
Balantidium
ctenopharyngodoni
GU480804 Eremoplastron rostratum AM158469
Balantidium entozoon EU581716 Eudiplodinium maggii U57766
Bandia cribbi AF298824 Gassovskiella galea AB793783
Bandia deveneyi AY380823 Helicozoster indicus AB794981
Bandia smalesae AF298822 Hemiprorodon
gymnoprosthium
AB795028
Bandia tammar AF298823 Isotricha intestinalis U57770
Bitricha tasmaniensis AF298821 Isotricha prostoma AF029762
Blepharoconus hemiciliatus AB795027 Latteuria media AB794983
Blepharocorys angusta AB794976 Latteuria polyfaria AB794982
Blepharocorys curvigula AB534184 Macropodinium ennuensis AF298820
Blepharocorys jubata AB794977 Macropodinium yalabense AF042486
Blepharocorys microcorys AB794975 Neobalantidium coli AF029763
Blepharocorys uncinata AB530162 Ochoterenaia appendiculata AB794973
Bozasella sp AB793744 Ophryoscolex caudatus AM158467
Bundleia benbrooki AB555711 Ophryoscolex purkynjei U57768
Bundleia nana AB555712 Ostracodinium clipeolum AB536717
Bundleia postciliata AB555709 Ostracodinium gracile AB535662
Buxtonella sulcata AB794979 Paraisotricha colpoidea EF632075
Circodinium minimum AB794974 Paraisotricha minuta AB794984
Cochliatoxum periachtum EF632078 Parentodinium sp. AB530164
Cycloposthium bipalmatum AB530165 Polycosta roundi AF298819
Cycloposthium edentatum EF632077 Polycosta turniae AF298818
Cycloposthium ishikawai EF632076 Polydiniella mysorea AB555710
Dasytricha ruminantium U57769 Polyplastron multivesiculatum U57767
Didesmis ovalis AB795025 Prorodonopsis coli AB795029
Diplodinium dentatum U57764 Pseudoentodinium elephantis AB794972
Diploplastron affine AM158457 Raabena bella AB534183
Ditoxum funinucleum AB794091 Spirodinium equi AB794092
Entodinium caudatum U57765 Sulcoarcus pellucidulus AB795024
Entodinium dubardi AM158443 Tetratoxum parvum AB794969
Entodinium longinucleatum AB481099 Triadinium caudatum AB530163
Entodinium nanellum JX876561 Tripalmaria dogieli EF632074
Entodinium simplex AM158466 Triplumaria selenica AB533538
Epidinium caudatum U57763 Troglodytella abrassarti AB437346
137
Table 4-3 Comparison of statistical parameters and results for three primer sets.
P-SSU-
316F
GIC758R
GIC1080F
GIC1578R
GIC1184F
GIC1578R
Total sequences before quality assurance steps 19,886 10,143 8,611
Total sequences after quality assurance steps 12,326 6,070 8,265
Unique sequences used for BLAST 769 697 424
Trimmed sequence length (bases) 450 b 450 b 375 b
Subsampled unique sequences used for
statistical analysis 424 424 424
Species-level distance within genera1 0.036 0.039 0.042
Recommended % cutoff for species-level
OTUs 4% 4% 4%
Observed species-level OTUs 48 25 20
CHAO 112 58 42
ACE 226 92 145
Shannon-Weaver 2.36 1.02 1.37
Good’s Coverage 0.94 0. 96 0.97
Inverse Simpson 4.69 1.71 2.59
Genus-level distance across genera2 0.087 0.079 0.096
Recommended % cutoff for genera-level OTUs 9% 8% 10%
Observed genus-level OTUs 15 14 12 1 Using near full-length 18S rRNA gene sequences from valid species, the species-level cutoff was
calculated to be 0.031. 2 Using near full-length 18S rRNA gene sequences, the genus-level cutoff was calculated to be 0.071.
4.10 Supplemental Material
Supplemental Material from this publication includes four lower triangle charts of genetic
distance comparisons, which are too large to be included in this text. Supplemental
Material can be accessed from the journal Applied and Environmental Microbiology:
http://aem.asm.org/content/early/2014/06/23/AEM.01644-14/suppl/DCSupplemental
138
CHAPTER 5 HIGH-THROUGHPUT DNA SEQUENCING OF THE MOOSE
RUMEN FROM DIFFERENT GEOGRAPHICAL LOCATION REVEALS A
CORE RUMINAL METHANOGENIC ARCHAEAL DIVERSITY AND A
DIFFERENTIAL CILIATE PROTOZOAL DIVERSITY.
Suzanne L. Ishaq1,*
, Monica A. Sundset2, John Crouse
3, and André-Denis G. Wright
1,4
*1 Department of Animal Science, University of Vermont, Burlington, Vermont, 05401
2 Department of Arctic and Marine Biology, University of Tromsø, Tromsø, Norway,
9019
3 Alaska Department of Fish and Game, Soldotna, Alaska, 99669
4 Present address: School of Animal and Comparative Biomedical Sciences, University
of Arizona, Tucson, Arizona 85721
*Contact: Suzanne Ishaq, Department of Animal Science, University of Vermont, 203
Terrill Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-
802-656-8196.
Keywords: 16S rRNA/ 18S rRNA/ 454 Roche Titanium/ Alaska/ MiSeq/ Norway/
rumen/ Vermont
139
5.1 Abstract
Moose rumen samples from Vermont, Alaska, and Norway were investigated for
methanogenic archaeal and protozoal density using real-time PCR, and diversity using
high-throughput sequencing of the 16S rRNA and 18S rRNA gene, respectively.
Vermont moose showed the highest protozoal and methanogen densities. Alaskan
samples had the highest percentages of Methanobrevibacter smithii, followed by the
Norwegian samples. One Norwegian sample contained 43% Methanobrevibacter thaueri,
while all other samples contained <10%. Vermont samples had large percentages of
Methanobrevibacter ruminantium, as did two Norwegian samples. Methanosphaera
stadtmanae represented one third of sequences in three samples. Samples were
heterogeneous based on gender, geographic location, and weight class using AMOVA,
but did not cluster significantly using PCoA or Unifrac. Two Alaskan moose contained
>70% Polyplastron multivesiculatum, and one contained >75% Entodinium sp. Protozoa
from Norwegian moose belonged predominantly (>50%) to the genus Entodinium,
especially Ent. caudatum. Norwegian moose also contained a large proportion of
sequences (25-97%) which could not be classified beyond Ophryoscolecidae. Protozoa
from Vermont samples were predominantly Eudiplodinium rostratum (>75%), with up to
7% Diploplastron affine. Four of the eight Vermont samples also contained 5-12%
Entodinium spp. Samples were heterogeneous based on AMOVA, PCoA, and Unifrac.
Previously, Alaskan moose were speculated to consume a higher starch diet than
Vermont moose, which were presumably consuming a higher forage diet.
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5.2 Introduction
Previous investigations into the microorganisms in the rumen of the moose have focused
on bacteria using cultivation [1] and high-throughput sequencing techniques [2, 3], or on
protozoa using light microscopy [4–7] and high-throughput sequencing [8].
Methanogenic archaea in the rumen of moose have not been previously identified, nor
have methanogens or protozoa from moose been compared across samples from different
geographic locations. Methanogens and protozoa in the rumen are often found in
intracellular or extracellular symbiotic associations involving hydrogen transfer from
protozoa to methanogens. Previously, protozoa from the genera Entodinium,
Polyplastron, Epidinium, and Ophryoscolex have been shown to interact with
methanogens from the orders Methanobacteriales and Methanomicrobiales [9].
The objectives of this research were to identify the methanogens and protozoa present in
the rumen of moose from Alaska, Vermont, and Norway; to measure the density of
methanogens and protozoa in these samples; to compare samples across geographic
location, gender, and weight class to determine possible trends; and to compare samples
to published studies on wild and domesticated ruminants. It was hypothesized that moose
may have fewer total methanogens than domestic ruminants due to a fast rate of passage
through the gastrointestinal tract [10]. In previous studies, age [3, 11, 12] and geographic
location [3, 13] have played a role in differentiating core bacterial microbiomes, and it
was also hypothesized that this would hold true for methanogens in the moose rumen.
141
However, reindeer in various geographic locations have been shown to have similar
protozoal diversity, indicating that the host species may have been isolated long enough
to develop a common profile regardless of geographic location of the host [14].
5.3 Methods
A total of 17 samples were collected from the rumen of moose in Vermont, USA (n=8)
(Oct 2010), Troms County, Norway (n=6) (Sept-Oct 2011), and Soldotna, Alaska (n=3)
(Aug 2012). Sample collection and DNA extraction were previously described [3].
Metadata for each sample collected, including gender, weight, approximate age, and
coordinates of sample collection have also been published elsewhere [3]. Pooled samples
from Alaska (n=3) were previously sequenced and described [8]. Samples were
identified by location (Alaska=AK, Norway=NO, and Vermont=VT), host (m=moose),
individual moose (1-8), and by sample material (r= rumen), consistent with previous
publications [2, 3, 8].
PCR was performed on a C1000 ThermalCycler (Bio-Rad, Hercules, CA) using the
Phusion kit (ThermoScientific, CA) to amplify rDNA. For methanogenic archaea, the V1
to V3 region of the archaeal 16S rRNA gene was amplified using primers 86F (5’-
GCTCAGTAACACGTGG-3’) [15] and 471R (5’-GWRTTACCGCGGCKGCTG-3’)
[16]. The protocol was as follows: initial denaturing at 98°C for 10 min, then 35 cycles
of 98°C for 30s, 58°C for 30s, 72°C for 30s, then a final elongation step of 72°C for 6
142
min. For ciliate protozoa, the V3-V4 and signature regions 1-2 of the 18S rRNA gene
were amplified using primers P-SSU-316F (5’-GCTTTCGWTGGTAGTGTATT-3’) [17]
and GIC758R (5’-CAACTGTCTCTATKAAYCG-3’) [8] following previously described
conditions [8]. PCR amplicons were verified on an agarose gel (100V, 60 min), and
DNA bands were excised and purified as previously described [3]. Amplicons were sent
to MR DNA Laboratories (Shallowater, TX) for MiSeq ver. 3 (methanogens) or Roche
454 pyrosequencing with Titanium (protozoa).
5.3.1 Sequence analysis
All sequences were analyzed using MOTHUR ver. 1.31 [18]. For methanogens,
sequence analysis was as previously described [3], with the following modifications.
Sequences were trimmed to a uniform length of 436 alignment characters (minimum 350
bases), and candidate sequences were aligned against the Ribosomal Database Project
(RDP) reference alignment integrated into MOTHUR with the bacterial sequences
removed. Sequences were classified using the k-nearest neighbor method against the full
RDP alignment, which had been modified to include species-level taxonomy. A 2%
genetic distance cutoff was used to designate species. For protozoa, sequence analysis
was as previously described for primer set 1, using a 4% genetic distance cutoff to
designate species [8]. For each sample, sequences were subsampled, and CHAO [19],
ACE [20], Good’s Coverage [21] and the Shannon-Weiner Index [22] were calculated.
143
An analysis of molecular variance (AMOVA) and Unifrac [23] were used to compare the
heterogeneity of samples.
5.3.2 Real-time PCR
Real-time PCR was used to calculate archaeal and protozoal densities in whole samples.
DNA was amplified using a CFX96 Real-Time System (Bio-Rad, CA) and a C1000
ThermalCycler (Bio-Rad, CA). Data were analyzed using CFX Manager Software ver.
1.6 (Bio-Rad, CA). The iQ SYBR Green Supermix kit (Bio-Rad, CA) was used: 12.5µL
of mix, 2.5µl of each primer (40mM), 6.5µL of ddH2O, and 1µL of the initial DNA
extract diluted to approximately 10 ng/μL. For methanogens, the primers targeted the
methyl coenzyme-M reductase A gene (mcrA), following the protocol by Denman et al.
[24]. The internal standards for methanogens were a mix of Methanobrevibacter smithii,
M. gottschalkii, M. ruminantium and M. millerae (R2=0.998).
For protozoa, the primers, PSSU316F and PSSU539R [17], targeted the 18S rRNA gene,
following the protocol by Sylvester et al. [17], and the internal standards for protozoa
were created in the laboratory using fresh rumen contents which were filtered through
one layer of cheesecloth to remove large particles, and then the protozoa were allowed to
separate for two hours at 39°C. Once a protozoal pellet was visible, 50 ml were drawn
from the bottom of the funnel, and 1 volume of ethanol was added to fix the cells and
DNA. The mix was centrifuged for 5 min at 2,000 x G, the pellet was washed with TE
buffer (1MTris-HCl, 0.5 M EDTA, pH 8.0) and then centrifuged again. Cells were
144
counted microscopically using a Thoma Slide following the protocol by Dehority [5],
(R2=0.998). Both protocols were followed by a melt curve, with a temperature increase
0.5°C every 10s from 65ºC up to 95°C to check for contamination.
5.4 Results
5.4.1 Methanogens
A total of 141,368 sequences, of which, 47,370 were unique sequences, passed quality
assurance steps. For each sample, between 22 and 330 OTUs were assigned using a 2%
genetic distance cutoff, giving a total of 1,942 non-redundant OTUs. CHAO, ACE,
Good’s Coverage and Shannon-Weaver Diversity for each sample are provided in Table
1. The Vermont samples showed the highest Shannon index, CHAO, and ACE, while the
Norwegian samples showed the highest Good’s Coverage. The Alaskan samples showed
the highest observed OTUs. Although there were few shared OTUs among samples,
these shared OTUs represented a large number of shared sequences (Table 2).
Comparing all 17 samples across different factors using AMOVA, groups were
heterogeneous based on gender (p<0.001), geographic location (p=<0.001), and weight
class (p<0.001). In contrast, samples did not cluster significantly based on gender or
weight class using PCoA (Figure 1 A,C,E), although Vermont clustered separately from
Norway and Alaska. When comparing samples using Unifrac, all samples again did not
cluster significantly using either weighted (0.17, p<0.001) or unweighted (0.91, p=0.20)
145
parameters. However, 16 out of 136 pairwise sample comparisons were significantly
different (p<0.001).
Vermont samples contained the highest mean density of methanogens at 1.3E+10,
followed by Alaskan samples and Norwegian samples (5.19E+09 and 3.58E+09,
respectively) (Table 3). Alaskan samples had the highest percentages of
Methanobrevibacter (Mbr.) smithii (16 to 36%), followed by the Norwegian samples (10
to 24%) (Figure 2). The Norwegian sample NO1R, contained the highest percentage of
Mbr. thaueri (43% of total sequences), while all other samples contained <10%.
Vermont samples had large percentages of Mbr. ruminantium (27-51% of total
sequences), as did the Norwegian samples NO3R and NO4R (40 and 41%, respectively)
(Figure 2). Methanosphaera stadtmanae was highest in NO5R (36%), VT8R (35%), and
NO6R (34%) (Figure 2). Less than 36 sequences total were found of each of the
following: Methanocella, Methanospirillum, Methanolobus, Methanosarcina,
Picrophilus, Methanobacterium, Mbr. curvatus, Mbr. cuticularis, or Unclassified at the
genus level (“Other”, Figure 2).
5.4.2 Protozoa
A total of 499,152 sequences, of which, 72,091 were unique sequences, passed quality
assurance steps. For each sample, between 1 and 31 OTUs were estimated using a 4%
genetic distance cutoff, giving a total of 110 non-redundant OTUs. CHAO, ACE, Good’s
146
Coverage and Shannon-Weaver Diversity index for each sample are provided in Table 1.
Both Norwegian and Vermont samples had extremely high coverage (>0.97%), yet low
Shannon diversity, CHAO and ACE values. Although there were few shared OTUs
among samples, these shared OTUs represented a large number of shared sequences
(Table 2). When comparing samples using Unifrac, samples clustered significantly using
weighted (0.71, p<0.001) and unweighted (0.93, p<0.001) parameters. When comparing
the Norway and Vermont samples across different factors using AMOVA, groups were
heterogeneous based on gender (p<0.001), geographic location (p=<0.001), and weight
class (p<0.001). This was also confirmed using PCoA for gender, location, and weight
class (Figure 1B, D, F).
Vermont samples contained the highest mean density of protozoa at 4.70E+06, followed
by Alaskan samples and Norwegian samples (3.83E+06 and 5.17E+04, respectively)
(Table 3). Using a previously described reference alignment and taxonomy of valid
protozoal sequences [8], protozoa were identified (Figure 3). Two Alaskan moose
contained >70% Polyplastron multivesiculatum, and one contained >75% Entodinium sp.
Protozoa from Norwegian moose belonged predominantly (>50% of total sequences) to
the genus Entodinium, especially Ent. caudatum (Figure 3). Norwegian moose also
contained a large proportion of sequences (25-97% of total sequences) which could not
be classified beyond the Ophryoscolecidae family (Figure 3). Protozoa from Vermont
samples were predominantly composed of Eudiplodinium rostratum (>75% of total
147
sequences). Vermont samples also contained up to 7% Diploplastron affine (Figure 3).
Many other species were identified in moose, with <1% each of the following identified:
Anoplodinium denticulatum, Dasytricha spp., Diplodinium dentatum, Enoploplastron
triloricatum, Entodinium bursa, Ent. dubardi, Ent. furca dilobum, Ent. furca monolobum,
Ent. longinucleatum, Ent. simplex, Epidinium caudatum, Epi. ecaudatum caudatum,
Epidinium spp., Eremoplastron dilobum, Eremoplastron rostratum, Eudiplodinium
maggii, Isotricha intestinalis, Isotricha prostoma, Metadinium medium, Metadinium
minorum, Ophryoscolex purkynjei, Ophryoscolex spp., Ostracodinium clipeolum,
Ostracodinium dentatum, Ostracodinium gracile, and Ostracodinium spp.
5.5 Discussion
The present study represents the first insight into the methanogenic archaeal diversity in
the rumen of the moose. Two of three Alaskan moose, as well as two of six Norwegian
moose had a larger proportion of methanogens belonging to the SGMT clade (Mbr.
smithii, Mbr. gottschalkii, Mbr. millerae, and Mbr. thaueri). All eight Vermont moose,
one Alaskan moose and four Norwegian moose had greater proportions of members of
the RO clade (Mbr. ruminantium and Mbr. olleyae). Previously, the SGMT clade was
show to be prevalent in alpaca [25], sheep [26], and reindeer [27]. As with bacteria in a
previous study [3], Alaskan moose shared a large number of methanogenic sequences,
followed by the Norwegian samples, and females shared more archaeal and protozoal
148
sequences than males. Unlike previously, the 202-300 kg weight class shared the greatest
number of archaeal and protozoal sequences of all the weight classes.
Methanobrevibacter smithii, unlike many other methanogens, has been shown to grow at
less than neutral pH [28], is often associated with high-calorie diets, has been shown to
influence weight gain in rats [29], and has been shown to improve polysaccharide
fermentation by bacteria [30, 31]. Conversely, Mbr. ruminantium has been associated
with a low-energy (high forage) diet [32]. Previously, Alaskan moose were speculated to
be on a higher starch/energy diet than those of Vermont moose, presumably on a higher
forage/lower energy diet [2], which may account for the relatively high proportions of
Mbr. smithii in Alaskan moose and high proportions of Mbr. ruminantium in Vermont
moose in the present study. Methanosphaera stadtmanae has previously been associated
with diets involving fruit, as they require methanol which is a byproduct of pectin
fermentation, as has been previously seen in omnivores [33, 34] and ruminants [16, 35,
36]. Though distinct in terms of proportion of taxa present in each of the three moose
populations, the samples were not statistically different between populations. This
suggests that moose have a core methanogen microbiome, as has been suggested for
protozoa in other host species [14].
In the present study, protozoa from Alaska, Norway, and Vermont were distinctly
different. Norwegian samples were dominated by Entodinium spp., while Vermont
149
samples were dominated by Polyplastron multivesiculatum and Eudiplodinium maggii.
The previously published data are limited by the fact that protozoal sequences were
generated using mixed amplicons from three Alaskan moose, not sequenced individually
[8].
Previously, using light microscopy, moose were shown to have primarily Entodinium
spp., including Ent. dubardi and Ent. longinucleatum in Alaska [5], Ent. dubardi and
other Entodinium spp. from Slovakia, and Ent. dubardi and Epi. caudatum in Finish
Lapland [7]. More recently using high-throughput sequencing, moose in Alaska were
shown to have a high percentage of Polyplastron multivesiculatum, and well as a variety
of Entodinium and other species [8], which was also shown in the present study. The
Norwegian samples had a high percentage of Ent. caudatum, Ent. furca dilobum, and
other Entodinium species, giving them a similar profile to moose samples from Alaska
[5], Finland [7], and Slovakia [6] using light microscopy. The Norwegian samples also
contained a large proportion of sequences which could not be identified beyond the
family level, indicating that these moose host novel ciliate species, or that no 18S rRNA
sequences exist for previously identified species.
Given the markedly different protozoal populations found in Alaska, Vermont, and
Norway, as well as the AMOVA analysis confirming statistically different groups, it may
be concluded that moose do not have a typical protozoal diversity as do reindeer [14].
150
Factors such as diet [27, 37, 38], and weaning strategy [39] have an effect on numbers
and type of protozoa. Previously, total protozoal counts were shown to be elevated in
concentrate selectors [38], while Entodinium populations were decreased in animals fed a
higher concentrate diet over those fed a roughage diet [38]. Entodinium spp. are a major
source of starch digestion in the rumen, as well as bacterial digestion [40]. Polyplastron
multivesiculatum produces xylanase and other carbohydrate-degrading enzymes [41],
which allows it to break down hemicellulose in plant cell walls and contribute to fiber
digestion. Eudiplodinium spp. also preferentially ingest structural carbohydrates [42, 43].
It has been shown that protozoal density affects methanogen density [37, 44], as the two
microbial communities are often symbiotically associated with one another. In particular,
Polyplastron, Eudiplodinium maggii, and Entodinium caudatum have been shown to have
>40% association with methanogens [45]. More specifically, Polyplastron was recently
shown to associate with Methanosphaera stadtmanae and Mbr. ruminantium [46].
Methanogen and protozoal densities in reindeer from Norway [47] averaged very closely
to densities found in Norwegian moose, but lower than in Alaskan and Vermont moose.
Domestic steers fed a roughage diet had an average density of 1.34E+09 for
methanogens, which were predominantly Methanobrevibacter spp. [24], and which was
lower than the present study. Holstein dairy cattle on a high-forage diet had an average
density of 6.04E+05 for protozoa [17], which were 2 logs less than densities in moose. It
151
was also shown that densities decreased on a low-forage diet, and the dominant genus
was Entodinium spp. [17]. Roughage diets in livestock have been shown to increase
methane emissions [48], even when the roughage diets are not associated with altered
methanogen densities [32, 49].
5.6 Acknowledgements
Acknowledgments The authors would like to acknowledge the Vermont Fish and
Wildlife Department for sample collection logistics; Terry Clifford, Archie Foster, Lenny
Gerardi, Ralph Loomis, Beth and John Mayer, and Rob Whitcomb for collection of
Vermont moose samples; Dr. Even Jørgensen, University of Tromsø, and Dr. Helge K.
Johnsen, University of Tromsø, for collection of Norwegian moose samples; and Dr.
Kimberlee Beckmen of the Alaska Department of Fish & Game for collection of Alaskan
moose samples.
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5.8 Figures
Figure 5-1 PCoA of moose (A, C, and E) and protozoa (B, D, and F).
A, B are colored for gender (red=female and blue=male) for methanogens and protozoa, respectively. C, D
are colored for location (red=Alaska, green= Norway, and blue=Vermont) for methanogens and protozoa,
respectively. E, F are colored for weight class (na= red, 1-100 kg= dark blue, 101-200= right facing green,
201-300=down facing green, 301-400= yellow, 400+= light blue) for methanogens and protozoa,
respectively.
158
Figure 5-2 Moose rumen methanogen taxonomy of total sequences, per sample from Alaska, Norway
and Vermont
“Other” represents the following taxa which has <1% Methanocella, Methanospirillum, Methanolobus,
Methanosarcina, Picrophilus, Methanobacterium, Mbr. curvatus, Mbr. cuticularis, or Unclassified at the
genus level.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
AK
M1R
AK
M2R
AK
M3R
NO
M1R
NO
M2R
NO
M3R
NO
M4R
NO
M5R
NO
M6R
VT
M1R
VT
M2R
VT
M3R
VT
M4R
VT
M5R
VT
M6R
VT
M7R
VT
M8R
Other
Mbr. wolinii
Mbr. woesei
Mbr. sp.ATM
Mbr.
arboriphilus
Msph.
stadtmanae
Mbr.
gottschalkii
Mbr. millerae
Mbr. thaueri
Mbr. smithii
Mbr. olleyae
Mbr.
ruminantium
159
Figure 5-3 Moose rumen protozoal taxonomy of total sequences, per sample from Norway and
Vermont.
Other species constitute <1% each of the following: Anoplodinium denticulatum, Dasytricha spp.,
Diplodinium dentatum, Enoploplastron triloricatum, Entodinium bursa, Ent. dubardi, Ent. furca dilobum,
Ent. furca monolobum, Ent. longinucleatum, Ent. simplex, Epidinium caudatum, Epi. ecaudatum caudatum,
Epidinium spp., Eremoplastron dilobum, Eremoplastron rostratum, Eudiplodinium maggii, Isotricha
intestinalis, Isotricha prostoma, Metadinium medium, Metadinium minorum, Ophryoscolex purkynjei,
Ophryoscolex spp., Ostracodinium clipeolum, Ostracodinium dentatum, Ostracodinium gracile, and
Ostracodinium spp.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
AK
M1R
AK
M2R
AK
M3R
NO
M1R
NO
M2R
NO
M3R
NO
M4R
NO
M5R
NO
M6R
VT
M1R
VT
M2R
VT
M3R
VT
M4R
VT
M5R
VT
M6R
VT
M7R
VT
M8R
Other
Diploplastron
affine
Entodinium
nanellum
Entodinium
caudatum
Entodinium
unclassified
Ophryoscolecidae
unclassified
Polyplastron
multivesiculatum
Eudiplodinium
rostratum
160
5.9 Tables
Table 5-1 Statistical measures per sample for methanogens (met) and protozoa (prot) in Alaska (AK),
Norway (NO), and Vermont (VT). Samples were subsampled using the smallest group for methanogens and protozoa. Species-level cutoff
was 2% for methanogens and 4% for protozoa.
Subsampled Sequences
Sample Total
seqs
Total
OTUs OTUs CHAO ACE
Good’s
Coverage
Shannon-
Weiner
Methanogens
AKM1R 4366 152 18 161 14 0.93 0.47
AKM2R 537 23 20 200 0 0.92 0.52
AKM3R 53648 292 6 17 10 0.98 0.15
Mean 19517 156 15 126 8 0.94 0.38
NOM1R 506 22 22 232 0 0.91 0.56
NOM2R 1830 79 19 163 26 0.93 0.48
NOM3R 19990 70 6 16 5 0.98 0.14
NOM4R 1355 33 15 115 0 0.94 0.39
NOM5R 17130 293 12 56 39 0.96 0.30
NOM6R 7106 70 9 32 41 0.97 0.24
Mean 7986 95 14 102 19 0.95 0.35
VTM1R 2351 102 26 262 328 0.90 0.70
VTM2R 1803 63 23 213 105 0.91 0.59
VTM3R 12855 99 11 46 111 0.96 0.31
VTM4R 4477 149 22 219 47 0.91 0.56
VTM5R 1180 82 38 470 675 0.85 1.02
VTM6R 3142 155 29 325 275 0.89 0.77
VTM7R 790 43 28 389 0 0.89 0.73
VTM8R 8302 330 31 359 538 0.88 0.81
Mean 4363 128 26 285 260 0.90 0.69
Protozoa
AKM1R 81387 31 1 1 0 1.00 0.01
AKM2R 57698 31 1 1 0 1.00 0.01
AKM3R 16200 12 1 1 0 1.00 0.01
Mean 51762 25 1 1 0 1.00 0.01
NOM1R 24605 1 1 1 0 1.00 0.00
NOM2R 15468 4 2 2 0 0.99 0.05
NOM3R 20351 9 3 4 0 0.97 0.14
NOM4R 5354 1 1 1 0 1.00 0.00
NOM5R 35189 7 2 2 0 0.99 0.06
NOM6R 30145 7 2 2 0 0.99 0.08
161
Mean 21852 5 2 2 0 0.99 0.06
VTM1R 24635 2 2 2 0 0.99 0.08
VTM2R 27901 6 2 2 0 0.99 0.06
VTM3R 41131 8 4 7 2 0.96 0.25
VTM4R 27612 3 1 1 0 0.99 0.03
VTM5R 30065 5 3 4 0 0.97 0.15
VTM6R 8334 3 3 3 0 0.98 0.12
VTM7R 27742 2 2 2 0 0.99 0.04
VTM8R 25335 1 1 1 0 1.00 0.00
Mean 26594 4 2 3 0 0.98 0.09
Table 5-2 The number of shared OTUs and unique sequences across different samples in Alaska
(AK), Norway (NO), and Vermont (VT).
Cutoff values of 2% for methanogens and 4% for protozoa were used to generate OTUs.
Methanogens Protozoa
Samples Compared Shared
OTUs
Unique
Seq
Shared
OTUs
Unique
Seq
All samples (n=17) 1 44967 1 48850
AK samples (n=3) 2 19888 2 45572
NO samples (n=6) 2 16227 2 1771
VT samples (n=8) 2 11255 2 1635
All Females (n=11) 2 31300 2 47400
All Males (n=6) 2 16070 2 1578
0-100 kg (NO1R, NO6R) 2 2684 2 519
101-200 kg (NO2R, VT1R, VT3R) 4 4804 2 528
201-300 kg (NO3R, NO5R, VT2R,
VT6R) 2 14007 2 1384
301-400 kg (VT5R, VT7R, VT8R) 2 3729 2 541
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Table 5-3 Real-time PCR results for methanogenic archaea and ciliate protozoa in Alaska (AK),
Norway (NO), and Vermont (VT).
Sample Corrected cells/ml rumen digesta archaea Corrected cells/ml rumen digesta
protozoa
AKM1R 3.33E+09 3.60E+06
AKM2R 1.91E+09 4.72E+05
AKM3R 1.03E+10 7.43E+06
Mean
(SE) 5.19E+09 (4.51E+09) 3.83E+06 (3.48E+06)
NO1R 8.66E+07 5.92E+03
NO2R 1.54E+08 1.10E+04
NO3R 1.95E+08 5.46E+04
NO4R 1.38E+08 7.26E+03
NO5R 2.17E+10 1.67E+05
NO6R 8.25E+08 6.45E+04
Mean
(SE) 3.58E+09 (8.76E+09) 5.17E+04 (6.20E+04)
VT1R 3.87E+09 2.14E+06
VT2R 1.88E+10 3.00E+06
VT3R 4.26E+10 9.02E+06
VT4R 1.98E+10 5.70E+06
VT5R 7.68E+09 6.53E+06
VT6R 8.93E+08 5.08E+05
VT7R 4.54E+09 5.50E+06
VT8R 6.02E+09 5.18E+06
Mean
(SE) 1.3E+10 (1.38E+10) 4.70E+06 (2.70E+06)
Mean
all (SE) 7.36E+09 (4.95E+09) 2.86E+06 (2.47E+06)
163
CHAPTER 6 DESCRIPTION OF STREPTOCOCCUS ALCIS, SP. NOV., AND
STREPTOCOCCUS VERMONTENSIS, SP. NOV., AND PROPOSAL OF
THREE NEW SUBSPECIES OF STREPTOCOCCUS GALLOLYTICUS
ISOLATED FROM THE RUMEN OF MOOSE (ALCES ALCES) IN
VERMONT.
Suzanne L. Ishaq1*, Doug G. Reis2, Hannah M. Lachance1, and André-Denis G.
Wright1,3
1 Department of Animal Science, College of Agriculture and Life Sciences, University of
Vermont, 570 Main St., Burlington, Vermont 05405
2 Department of Microbiology and Molecular Genetics, College of Agriculture and Life
Sciences, University of Vermont, 95 Carrigan Drive., Burlington, Vermont 05405
3 Present Address: School of Animal and Comparative Biomedical Sciences, College of
Agriculture and Life Sciences, University of Arizona, 1117 E. Lowell Street, Tucson,
Arizona. 85721
* Suzanne Ishaq, Department of Animal Science, University of Vermont, 203 Terrill
Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-802-656-
8196.
Email addresses: SLI: slpelleg@uvm.edu, DR: dreis@uvm.edu, HL:
hannah.lachance@uvm.edu, ADGW: adwright@email.arizona.edu
Contents Category: New Taxa (Firmicutes)
Keywords/Cross-reference: 16S rRNA gene, anaerobic culturing, bacteria
GenBank ASCN: KP009806-KP009843
164
6.1 Summary
Standard anaerobic and aerobic culturing techniques were used to isolate,
characterize, and investigate the functional abilities of 37 isolates of Streptococcus
bacteria from the rumen of the North American moose. Isolates were able to grow at
higher temperatures and salinities than previously described cultivars, and at a wider
range of pH. All 37 isolates produced acid from fructose, galactose, glucose, glycerol,
lactose, maltose, mannitol, and sucrose. Variable numbers of isolates produced acid from
N-acetylglucosamine, arabinose, cellobiose, cellulose, inulin, mannose, melibiose,
raffinose, and salicin. Twenty-nine isolates produced a ropy exopolysaccharide, three
reduced tellurite, and one isolate produced indole from tryptophan. Two isolates did not
produce biogenic amines from amino acids. Twenty-four isolates are new strains of S.
gallolyticus subsp. gallolyticus, and can produce acid from glycogen, inulin, mannitol,
melibiose, and raffinose. Three isolates are new strains of S. gallolyticus subsp.
macedonicus, which are unable to produce acid from glycogen, inulin, mannitol,
melibiose, and raffinose. Nine isolates were not able to produce acid from glycogen or
raffinose. However, some were able to produce acid from inulin, mannitol or melibiose.
Based on the differential biochemical capabilities, DNA-DNA hybridizations, seven
house-keeping genes, and genetic distances, based upon 16S rRNA gene sequence, of 10
isolates, two new species: S. alcis sp. nov., and S. vermontensis sp. nov.; and three new
subspecies of S. gallolyticus are proposed: S. gallolyticus subsp. mannosilyticus subsp.
165
nov., S. gallolyticus subsp. melibiosilyticus subsp. nov., and S. gallolyticus subsp.
ruminantium subsp. nov.
This study used classical culturing techniques to isolate and characterize isolates of
Streptococcus gallolyticus from the rumen of the North American moose (Alces alces). It
was hypothesized that isolates from the moose rumen would be functionally distinct from
previously identified bacteria, and that they might be appropriate for food production.
Only a few studies have been published on the bacteria in the ruminal environment of
moose (Ishaq & Wright, 2014, 2012; Dehority, 1986).
Several species of the lactic acid bacteria (LAB) Streptococcus are non-
pathogenic and have been extremely important economically in the production of dairy
food products due to the secretion of an exopolysaccharide (EPS) that gives dairy
byproducts desired textures (Bolotin et al., 2004; Georgalaki et al., 2000; McSweeney,
2004; Papadimitriou et al., 2012; Tsakalidou et al., 1998; Vincent et al., 2001).
Streptococcus gallolyticus can tolerate high-salinity environments, like those found in
cheese making (Beresford et al., 2001). Many species of Streptococcus possess
decarboxylase enzymes, which make them capable of producing biogenic amines (i.e.
biologically active molecules) from different precursor amino acids. Biogenic amines
can cause a variety of adverse gastrointestinal and cardiovascular symptoms depending
on the amine and the dose. Streptococcus gallolyticus isolates which produced one or
166
more of these amines would be considered unfit candidates for food production
applications (Ladero et al., 2010; McSweeney, 2004).
Isolates were cultured from whole rumen digesta samples, which were collected
fresh, during the October 2010 hunting season in Vermont, with permission of licensed
hunters through the Vermont Department of Fish and Wildlife. For information on the
moose age and weight, see Ishaq and Wright (2012). All isolations were performed on
M8 agar (Bryant & Robinson, 1961; Dehority & Grubb, 1976) plates inside an anaerobic
chamber (90% nitrogen, 5% hydrogen, 5% carbon dioxide) (COY Laboratories,
Michigan, US). Samples were serially diluted, plated with 5 replicates, and monitored
for up to 1 week. Colonies were picked and re-isolated on fresh media until pure using
gram staining and colony morphology measurements, and monocultures were identified
using near full-length 16S rRNA gene sequencing performed at the University of
Vermont Cancer Center DNA Analysis Facility (Burlington, Vermont, US). The
bacterial 16S rRNA gene was amplified using the universal bacterial primers 27F and
1494R (Lane, 1991).
PCR was performed using the iTaq DNA Polymerase kit (Bio-Rad, California,
US) per kit instructions. PCR conditions were: initial denaturation of 94°C for 5 min,
then 33 cycles of 94°C for 30 s, 50°C for 30 s, and 72°C for 1 min, followed by a final
extension of 72°C for 6 min. PCR was performed on a C1000 thermal cycler (Bio-Rad,
California, US). Recalcitrant isolates were first extracted using the DNA extraction
protocol in the QIAamp DNA Stool Mini Kit (QIAGEN, Maryland, US).
167
Amplification was verified by 1% agarose gel electrophoresis (100V for 60
min), and the remaining PCR product was enzymatically cleaned with ExoSAP-IT
(Affymetrix, California, US). Cycle sequencing primers used included 27F, 1492R,
1494R, 907R (Lane, 1991), and 907F (Blackall et al., 1995). Sequences were proofread
using ChromasPro ver. 1.7.5 (Technelysium Pty. Ltd., Australia), and aligned using the
CLUSTALW algorithm in MEGA ver. 5.05 (Tamura et al., 2011). The alignment was
refined by eye, and then used to calculate pairwise genetic distance using the Kimura 2-
parameter model (Kimura, 1980). Sequences were identified using GenBank’s Basic
Local Alignment Search Tool (BLAST) (Altschul et al., 1990), and compared to
published sequences of lactic acid bacteria from NCBI using a neighbor-joining tree
generated with MEGA (Figure 1).
Near full-length sequences were generated for each isolate and deposited in
NCBI under accession numbers KP009806-KP009843. Sequences had 99% identity to
known sequences of S. gallolyticus subsp. macedonicus using BLAST. When clustered
using a neighbor-joining tree, 37 isolates clustered along with S. gallolyticus subsp.
macedonicus(T)
(Figure 1). Mean genetic identity among the isolates was 99.7% (range
97.7–100%). The mean sequence identity between individual isolates and S. gallolyticus
subsp. macedonicus(T)
was 99.5% (range 98.4–99.7%), while the mean sequence identity
between individual isolates and S. gallolyticus subsp. gallolyticus(T)
was 99% (range
97.6–99.27%). Thirty-six of 37 isolates had a higher percent identity to S. gallolyticus
subsp. macedonicus(T)
than to S. gallolyticus subsp. gallolyticus(T)
, the exception being
168
VTM3R19T. The novel isolates had the following sequence identity to S. gallolyticus
subsp. gallolyticus(T)
(VTM3R19T, 99%; VTM4R28
T, 99.2%; VT1R31
T, 95.5%;
VTM3R37T, 94.8%; VTM1R54
T, 95.4%) and S. gallolyticus subsp. macedonicus
(T)
(VTM3R19T, 99.3%; VTM4R28
T, 99.4%; VT1R31
T , 99.2; VTM3R37
T, 98.5%;
VTM1R54T, 98.8%).
Five isolates which were proposed new taxa were also classified based on seven
housekeeping genes as previously described [204]: guanylate kinase, gmk (AB829357-
AB829373); peroxide resistance, dpr (AB829337-AB829356); DNA topoisomerase IV
subunit A, parC (AB829398-AB829412); phosphate acetyltransferase, pta (AB829413-
AB829429); dihydrotase, pyrC (AB829430-AB82944); DNA repair protein, recN
(AB829451-AB829472); and RNA polymerase sigma factor, rpoD (AB829374-
AB829397). Isolates clustered separately from reference sequences for gmk, parC, pta,
recN (Figures 2A, 2C, 2D, 2F), and three of five clustered separately for rpoD (Figure
2G).
Monocultures were maintained on M8 media plates with sodium azide to
prevent potential contamination growth of gram negative species, then transferred to
MRS media (Downes & Ito, 2001; De Mann et al., 1960) for the duration of testing.
Before each test, isolates were subcultured in MRS broth (1% v/v inoculation) for 24 h,
and tests were run in triplicate. Stock aliquots of isolates were mixed with 80% glycerol
and stored at -80°C. Isolates were given unique identifiers (i.e. VTM3R11) containing
the following abbreviations: Vermont (VT), moose (M), individual number (1–4), and
169
rumen (R), as well as isolate number. All isolate colonies showed similar morphology:
small, white, irregular to round colonies with an opaque, glistening and butyrous
appearance. Cell morphologies were consistently non-motile, gram-positive cocci in
small chains or groups. All isolates were catalase negative.
Optimal growth parameters were determined by incubating isolates for 24 h at
various temperatures (25–49°C), pH (5.0–10.0) (adjusted prior to autoclaving), or
salinities (0–9% NaCl). Optical density (absorbance, 600 nm) was used to determine
relative growth using a Spectronic 200 (ThermoScientific, CA) (Georgalaki et al., 2002).
Optimal growth ranges were set as isolates measuring >0.5% absorbance. Optimal
temperature ranged from 31°C to 39°C, optimal salinity ranged from 0 to 3% NaCl, and
optimal pH ranged from pH 5.7 to 7.7 (Supplemental Figure 1). Six isolates were able to
grow above 1% absorbance at 25°C (VTM3R15, VTM1R33, VTM3R37T, VTM4R46,
VTM4R49, VTM4R51), and seven isolates were able to grow above 0.5% at 49°C
(VTM3R11, VTM3R26, VTM1R44, VTM4R46, VTM4R49, VTM1R50, VTM4R54).
Six isolates were able to grow above 0.5% at pH 5.0 and above 1% absorbance at pH
10.0 (VTM3R15, VTM2R16, VTM3R37T, VTM3R40, VTM4R46). Only three isolates
were able to grow above 0.5% at 9% NaCl (VTM1R54T, VTM3R42, VTM4R13). In the
present study, isolates tolerated high salinity environments, very high and low pH ranges,
and high and low temperatures: higher than previously described S. macedonicus (sic)
isolates (Tsakalidou et al., 1998).
170
Heat tolerance was tested by incubating 48 h old cultures in a 60°C water bath
for 30 min, then inoculating onto MRS agar plates and incubating at 37°C for up to 72 h
to observe for growth. Six isolates showed no change in growth after heat shock
(VTM1R14, VTM3R15, VTM4R46, VTM4R49, VTM4R51, VTM4R54), and three
isolates grew minimally (VTM1R44, VTM1R48, VTM3R32).
Ruthenium red (RR) plates (Stingele & Mollet, 1995) were used to determine if
isolates produced a ropy exopolysaccharide, which prevents RR staining the cell wall of
isolates. Because RR was ineffective at differentiating isolates if added to the media
before autoclaving as specified previously (Stingele & Mollet, 1995), an additional 0.2
g/L RR was added after autoclaving (i.e. 0.28 g/L). Twenty-nine isolates exhibited a
ropy exopolysaccharide, which is preferable in dairy byproducts (Table 1).
Isolates which produced a ropy exopolysaccharide then had extracellular protein
quantified using skimmed milk medium (SMM) (Dabour & LaPointe, 2005; De Vuyst et
al., 1998). The combined protocol is as follows: cultures were heat treated at 90°C for 15
min to inactivate enzymes, then centrifuged at 12,000 x g for 20 min at 4°C to pellet
bacterial cells, and 1 volume of 20% trichloroacetic acid was added to the supernatant to
precipitate protein. The supernatant was centrifuged at 16,000 x g for 20 min at 4°C to
pellet proteins. The supernatant was removed, the pellet air-dried, and then suspended in
ddH2O for the protein assay. The protein assay was performed using the Bio-Rad Protein
Assay Kit, (Bio-Rad, California, US), following the manufacturer’s instructions. Casein
171
was used to make protein standards, and assays were read using a Spectronic 200
(ThermoScientific, California, US).
Thirteen isolates produced between 0.5–1 mg/ml of protein each (Table 1). Data
are visualized in Supplemental Figure 2. The quality and quantity of EPS produced by
cultures are important for a successful consumer food product, as it contributes to product
structure, mouth feel, and texture (Folkenberg et al., 2005), especially in low-fat dairy
products, as it maintains the texture and structure that would normally be provided by fat,
and can be used in applications where stabilizers are unavailable for use (Patel &
Prajapati, 2013). In previous studies, some isolates produced no EPS (Georgalaki et al.,
2000).
To measure acid production, isolates were subcultured in skim milk (10% w/v),
and acid production was recorded as the pH value at 1 h, 6 h and 24 h (Georgalaki et al.,
2000), (Table 2), and is visualized in Supplemental Figure 3. In the present study, isolates
produced a similar amount of acid after 6 h of incubation as previously described isolates
(Georgalaki et al., 2000). Isolates were subcultured onto MRS agar plates containing the
pH indicator chlorophenol red, to test for acidic byproducts from different carbohydrates
(Georgalaki et al., 2000). All isolates produced acidic byproducts from D-fructose,
galactose, D+-glucose, glycerol, lactose, maltose and sucrose, and a variable number
produced acids from D-mannose, D-arabinose, salicin, N-acetylglucosamine, cellobiose,
melibiose, inulin, D-raffinose, and cellulose (Table 2). Streptococcus gallolyticus has
previously been shown to utilize cellobiose (Chamkha et al., 2002), and a presumptive
172
gene resembling that of a Ruminococcus albus endoglucanase has previously been
identified in S. gallolyticus (Rusniok et al., 2010). Streptococcus gallolyticus subsp.
gallolyticus can produce acid from glycogen, inulin, mannitol, melibiose, pullulan and
raffinose, all of which previous strains of S. gallolyticus subsp. macedonicus were unable
to do (Osawa et al., 1995; Schlegel, 2003; Tsakalidou et al., 1998).
Isolates were tested on mannitol media for their ability to metabolize mannitol
and tolerate potassium tellurite. All isolates fermented mannitol, and two reduced tellurite
and produced black precipitate (VTM3R11, VTM3R17). One isolate did not tolerate
potassium tellurite and was unable to grow (VTM1R33). Isolates were grown for 14 d to
test for the production of indole from tryptophan using Kovac’s reagent (Kovacs, 1928)
added to the culture broth. No isolates produced indole from tryptophan.
To determine whether isolates could hydrolyze esculin (and produce a black
precipitate), strains were plated on esculin media with and without the presence of bile
salts. Three isolates could not tolerate bile salts and exhibited no growth (VTM1R27,
VTM1R33, VTM1R50), while 35 isolates tolerated bile salts and hydrolyzed esculin.
Without bile salts, all 37 isolates were capable of hydrolyzing esculin. Streptococcus
gallolyticus subsp. gallolyticus can hydrolyze esculin (Osawa et al., 1995; Schlegel,
2003; Tsakalidou et al., 1998).
Isolates were subcultured into Simmon’s Citrate slants (Simmons, 1926) for 7d,
and observed for bacterial growth and color change, to indicate the ability use citrate as a
carbon source and ammonia as a nitrogen source (Georgalaki et al., 2000). Fifteen
173
isolates used citrate as their sole source of carbon and ammonium ions as their source of
nitrogen (Table 1). To test ability to reduce nitrate to nitrite, isolates were subcultured
into nitrate broth for 3 and 7 d and then tested for color change using potassium iodine
strips moistened with 1N HCl. Three isolates showed variable ability to produce nitrite
from nitrate after 3 d, and six more (n=12) isolates were positive after 7 d. Twenty-five
isolates showed lipase activity (Table 1), as determined by halo formation on MRS agar
plates (pH 6.8) with tributyrin (1% v/v) and arabic gum (1% w/v) (Georgalaki et al.,
2000).
To test biogenic amine production, isolates were inoculated on media containing
a precursor amino acid (2% w/v, ornithine, histidine, lysine, tyrosine) (Joosten &
Northolt, 1989), and observed for blue/green color formation around colonies
(Georgalaki et al., 2000). Most isolates produced biogenic amines from some precursor
amino acids, 11 isolates produced all four amines, and two produced none (Table 1).
Biogenic amines may be used to create functional foods, as some are involved in immune
response, cell growth, and homeostasis regulation (Ladero et al., 2010). However,
certain biogenic amines can be toxic in high concentrations and their presence in certain
foods is not preferred (Ladero et al., 2010). In the present study, isolates created
biogenic amines from histidine, lysine, ornithine, and tyrosine. In a previous study,
strains of Streptococcus produced little to no biogenic amine (Georgalaki et al., 2000).
Using biochemical profiles, as well as 16S sequencing, the present study
classified 24 isolates as S. gallolyticus subsp. gallolyticus and 3 isolates as S. gallolyticus
174
subsp. macedonicus. Based on the differential biochemical capabilities, DNA-DNA
hybridizations, seven house-keeping genes, and 16S rRNA genetic distances of 10
isolates, two new species, S. alcis sp. nov. and S. vermontensis sp. nov., and three new
subspecies of S. gallolyticus are proposed: S. gallolyticus subsp. mannosilyticus subsp.
nov., S. gallolyticus subsp. melibiosilyticus subsp. nov., and S. gallolyticus subsp.
ruminantium subsp. nov.
For the novel isolates, the type strain was tested for hemolysis pattern using 5%
sheep’s blood on tryptic soy agar (TSA) plates (ThermoScientific, California, US). Of
the two proposed novel species and three proposed novel subspecies, four were alpha-
hemolytic, and S. gallolyticus subsp. melibiosilyticus subsp. nov. (VTM3R37T) was non-
hemolytic. Each type strain was also genotypically characterized by DNA-DNA
hybridization. G+C content and DNA-DNA hybridization were calculated using a C1000
thermal cycler with CFX96 real-time system (Bio-Rad, California, US) and previously
published protocols (Bowman et al., 1998; Moreira et al., 2011). The reference strains
Streptococcus gallolyticus subsp. gallolyticus(T)
(ATCC 700065) (Osawa et al., 1995) and
S. gallolyticus subsp. macedonicus(T)
(ATCC BAA-249) (Tsakalidou et al., 1998) were
used. DNA-DNA hybridization was calculated using the change in melting temperature
(ΔTm) between the reference and hybrid strains (Moreira et al., 2011) using regression
equations created with previously published DNA-DNA hybridization data (Schlegel at
al., 2003). DDH, GC content, and ΔTm are presented in Table 3. G+C content ranged
from 37.7 to 38.1%, ΔTm was between 0.3 and 2.6°C, and % DNA-DNA hybridization
175
to reference strains was between 73 and 91%. The species-level cutoff for DNA-DNA
hybridization is 70%. However, previously published data on DNA-DNA hybridization
ranged from 50–100% for strains of S. gallolyticus subsp. gallolyticus, and 54–100% for
strains of S. gallolyticus subsp. macedonicus (Schlegel et al. 2003), indicating a high
degree of genetic variability even within a subspecies.
6.2 Description of Streptococcus alcis sp. nov.
Streptococcus alcis (al’cis. N.L. gen. n. alcis named after the moose, Alces alces, the
source of the type strain). Cells are Gram-positive cocci, occurring in pairs or short
chains, non-motile, non-sporulating, and catalase-negative. Colonies are circular, 1 mm
in diameter after 24 h at 37 °C, and white to unpigmented. Growth is enhanced in a 5%
CO2 atmosphere, and occurs in MRS broth without gas production. No growth in
6±0.5% (w/v) NaCl broth. Alpha hemolytic on 5% blood agar. The type strain of S.
alcis VTM1R28T
(= ATCC-00408-01T
= DSM XXXXT
=NCBI KP009833) was isolated
from the rumen of a 1-year old female moose in Vermont, USA. Produces acid from N-
Acetylglucosamine, arabinose, cellobiose, cellulose, fructose, galactose, glucose,
glycerol, glycogen, inulin, lactose, maltose, mannose, melibiose, raffinose, salicin and
sucrose. Exopolysaccharide is ropy in consistency. Biogenic amines produced from
histidine and lysine. Lipase is produced. It is tolerant of bile salts and can hydrolyze
esculin. It can use citrate as a sole carbon source and ammonium ions as a sole nitrogen
176
source. Characteristics useful in their differentiation from related organisms and also in
the delineation between the two subspecies are listed in Tables 1–3.
6.3 Description of Streptococcus vermontensis sp. nov.
Streptococcus vermontensis (ver.mont.en’sis. N.L. masc. adj. vermontensis named after
the U.S. state where the moose were captured, the source of the type strain). Cells are
Gram-positive cocci, occurring in pairs or short chains, non-motile, non-sporulating, and
catalase-negative. Colonies are circular, 1 mm in diameter after 24 h at 37 °C, and white
to unpigmented. Growth is enhanced in a 5% CO2 atmosphere, and occurs in MRS broth
without gas production. No growth in 6±0.5% (w/v) NaCl broth. Alpha hemolytic on
5% blood agar. The type strain of S. vermontensis VTM3R19T
(= ATCC-00408-06T
=
DSM XXXXXT =NCBI KP009835) was isolated from the rumen of a 2-year old male
moose in Vermont, USA. Produces acid from N-acetylglucosamine, arabinose,
cellobiose, fructose, galactose, glucose, glycerol, lactose, maltose, mannose, melibiose,
salicin and sucrose. Exopolysaccharide is non-ropy in consistency. Biogenic amines
produced from histidine, lysine, and ornithine. It is tolerant of bile salts and can
hydrolyze esculin. Characteristics useful in their differentiation from related organisms
and also in the delineation between the two subspecies are listed in Tables 1–3.
177
6.4 Description of Streptococcus gallolyticus subsp. mannosilyticus subsp. nov.
Streptococcus gallolyticus subsp. mannosilyticus (man.no.si.ly'ti.cus. N.L. neut. n.
mannosum mannose; N.L. masc. adj. lyticus (from Gr. neut. adj. lutikos), able to loosen,
able to dissolve; N.L. masc. adj. mannosilyticus breaking down mannose). Cells are
Gram-positive cocci, occurring in pairs or short chains, non-motile, non-sporulating, and
catalase-negative. Colonies are circular, 1 mm in diameter after 24 h at 37 °C, and white
to unpigmented. Growth is enhanced in a 5% CO2 atmosphere, and occurs in MRS broth
without gas production. Some growth in 6±0.5% (w/v) NaCl broth. Alpha hemolytic on
5% blood agar. The type strain of S. gallolyticus subsp. mannosilyticus VTM1R31T
(=ATCC-00408-03T
= DSM XXXXXT =NCBI KP009837) was isolated from the rumen
of a 1-year old female moose in Vermont, USA. Produces acids from fructose, galactose,
glucose, glycerol, lactose, maltose, mannose, and sucrose. Acid production from N-
Acetylglucosamine, arabinose, cellobiose, cellulose, and salicin is variable.
Exopolysaccharide is ropy or non-ropy in consistency. Biogenic amines produced from
lysine, and variably from histidine, ornithine, and tyrosine. Lipase is variably produced.
It is tolerant of bile salts and can hydrolyze esculin. Ability to use citrate as a sole carbon
source and ammonium ions as a sole nitrogen source is variable. Three strains of this
subspecies were also isolated from the moose rumen: VTM3R15, VTM1R44, and
VTM4R49. Characteristics useful in their differentiation from related organisms and also
in the delineation between the two subspecies are listed in Tables 1–3.
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6.5 Description of Streptococcus gallolyticus subsp. melibiosilyticus subsp. nov.
Streptococcus gallolyticus subsp. melibiosilyticus (me.li.bi.o.si.ly'ti.cus. N.L. neut. n.
melibiosum melibiose; N.L. masc. adj. lyticus (from Gr. neut. adj. lutikos), able to
loosen, able to dissolve; N.L. masc. adj. melibiosilyticus breaking down melibiose). Cells
are Gram-positive cocci, occurring in pairs or short chains, non-motile, non-sporulating,
and catalase-negative. Colonies are circular, 1 mm in diameter after 24 h at 37 °C, and
white to unpigmented. Growth is enhanced in a 5% CO2 atmosphere, and occurs in MRS
broth without gas production. Some growth in 6±0.5% (w/v) NaCl broth. Non (gamma)
hemolytic on 5% blood agar. The type strain of S. gallolyticus subsp. melibiosilyticus
VTM3R37T (=ATCC-00408-04
T = DSM XXXXX
T =NCBI KP009841) was isolated
from the rumen of a 1-year old female moose in Vermont, USA. Produces acid from
arabinose, cellobiose, cellulose, fructose, galactose, glucose, glycerol, lactose, maltose,
mannose, melibiose, salicin and sucrose. Acid production from N-Acetylglucosamine is
variable. Exopolysaccharide is ropy in consistency. Biogenic amines produced from
lysine, and variably from histidine, ornithine, and tyrosine. Lipase is variably produced.
It is tolerant of bile salts and can hydrolyze esculin. Ability to use citrate as a sole carbon
source and ammonium ions as a sole nitrogen source is variable. One strain of this
subspecies was also isolated from the moose rumen, VTM3R23. Characteristics useful in
their differentiation from related organisms and also in the delineation between the two
subspecies are listed in Tables 1–3.
179
6.6 Description of Streptococcus gallolyticus subsp. ruminantium subsp. nov.
Streptococcus gallolyticus subsp. ruminantium (ru.mi.nan’ti.um. L. part adj. ruminans -
antis, ruminating; N.L. pl. gen. n. ruminantium, of ruminants) named after the ruminant
rumen/forestomach where the bacteria resided. Cells are Gram-positive cocci, occurring
in pairs or short chains, non-motile, non-sporulating, and catalase-negative. Colonies are
circular, 1 mm in diameter after 24 h at 37 °C, and white to unpigmented. Growth is
enhanced in a 5% CO2 atmosphere, and occurs in MRS broth without gas production.
Some growth in 6±0.5% (w/v) NaCl broth. Alpha hemolytic on 5% blood agar. The type
strain of S. gallolyticus subsp. ruminantium VTM1R54T (=ATCC-00408-05
T = DSM
XXXXXT =NCBI KP009842) was isolated from the rumen of a 1-year old female moose
in Vermont, USA. Produces acid from arabinose, fructose, galactose, glucose, glycerol,
lactose, maltose, and sucrose. Acid production from cellulose and melibiose is variable.
Exopolysaccharide is ropy or non-ropy in consistency. Biogenic amines produced from
lysine, ornithine, and tyrosine. Lipase is produced. It is tolerant of bile salts and can
hydrolyze esculin. One strain (VTM4R54) of this subspecies was also isolated from the
rumen of moose in Vermont, US. Characteristics useful in their differentiation from
related organisms and also in the delineation between the two subspecies are listed in
Tables 1–3.
6.7 Conflict of interest
The authors declare no conflict of interest.
180
6.8 Acknowledgements
The authors would like to thank Sam Rosenbaum, Ken Wesley, and Emma Hurley for
their help in preparing culture media, collecting optical density data, and for general lab
maintenance; the Vermont Fish and Wildlife Department for their help in rumen sample
collection logistics; and Terry Clifford, Archie Foster, Lenny Gerardi, Ralph Loomis,
Beth and John Mayer, and Rob Whitcomb for collection of rumen samples.
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185
6.10. Figures
Figure 6-1 Neighbor-joining tree comparing isolates to type isolates to lactic acid bacteria.
Tree was generated using MEGA ver. 5.05 (Tamura et al., 2011) and the Kimura 2-parameter model
(Kimura, 1980). (T) = type strain, and numbers at the nodes represent bootstrap values. Lactobacillus
acidophilus (AB680529) and Enterococcus faecium (AJ301830) were used as out-groups.
186
Figure 6-2 UPGMA trees comparing novel isolates using the housekeeping genes gmk (A), dpr (B),
parC (C), pta (D), pyrC (E), recN(F), and rpoD (G).
187
Figure 6-2 UPGMA trees comparing novel isolates using the housekeeping genes gmk (A), dpr (B),
parC (C), pta (D), pyrC (E), recN(F), and rpoD (G).
188
Figure 6-2 UPGMA trees comparing novel isolates using the housekeeping genes gmk (A), dpr (B),
parC (C), pta (D), pyrC (E), recN(F), and rpoD (G).
189
Figure 6-2 UPGMA trees comparing novel isolates using the housekeeping genes gmk (A), dpr (B),
parC (C), pta (D), pyrC (E), recN(F), and rpoD (G).
190
6.11 Tables
Table 6-1Ability of isolates to produce biogenic amines from selected amino acids, produce lipase,
metabolize citrate, produce a ropy or non-ropy exopolysaccharide, and extracellular protein
production.
For biogenic amine production from ornithine, histidine, tyrosine and lysine, and lipase production results
are presented as positive (+), slight positive (~), and negative (-). Simmon’s Citrate results are presented as
positive (+) or negative (-) for both butt (anaerobic) and slant (aerobic) portions, as well as color change
(B). Exopolysaccharide results are presented by type: ropy or non-ropy (NR).
Isolates O
rnit
hin
e
His
tid
ine
Tyro
sin
e
Lysi
ne
Lip
ase
Sim
mon
s
(b/s
)
EP
S t
yp
e
Pro
tein
(mg/m
L)
Streptococcus gallolyticus subsp. gallolyticus
VTM3R11 - - + + + -/- Ropy 0.24
VTM3R12 + - - + + -/- Ropy 0
VTM4R13 + - + + - +/- Ropy n/a
VTM1R14 + - + + + -/- Ropy 0.32
VTM3R17 ~ - + + + +/- NR n/a
VTM4R20 + - + + - -/- Ropy 0.69
VTM3R21 + - + + + -/- Ropy 0.48
VTM3R22 + + + + + -/- Ropy 0.98
VTM3R24 + + + + - -/- Ropy 0.07
VTM1R25 - - - - + +B/- Ropy 0.59
VTM3R26 + - + + + -/- Ropy 0.91
VTM1R27 + + + + + + Ropy n/a
VTM1R29 + + + + + -/- Ropy 0.74
VTM3R32 + ~ + + ~ -/- Ropy 0.63
VTM1R35 + + - + - + Ropy 0.45
VTM1R38 - - - - ~ +/- Ropy 0.69
VTM1R41 ~ - + + - +/- Ropy 0.72
VTM3R42 + + + + + + Ropy 0.76
VTM2R45 + - ~ + - + Ropy n/a
VTM4R46 + - + + + +B/- Ropy 0.43
VTM2R47 + + + + + + NR n/a
VTM1R48 + + + + - -/- Ropy 0
VTM1R50 + + + + - + Ropy 0.3
VTM2R55 + - + + + -/- Ropy 0.69
Streptococcus gallolyticus subsp. macedonicus
VTM1R33 + + - - + -/- NR n/a
191
VTM2R39 + + - + + -/- Ropy 0.63
VTM4R51 + - + + - +B/+B NR n/a
Streptococcus alcis sp. nov.
VTM1R28T - + - + + +B/+ Ropy 0.41
Streptococcus vermontensis sp. nov.
VTM3R19T + - + + - -/- NR n/a
Streptococcus gallolyticus subsp. mannosilyticus subsp. nov.
VTM3R15 - - - + ~ -/- NR n/a
VTM1R31T + ~ + + - -/- Ropy 0.38
VTM1R44 + - + + + + Ropy 0.27
VTM4R49 + - + + + +B/+B NR n/a
Streptococcus gallolyticus subsp. melibiosilyticus subsp. nov.
VTM3R23 + + + + - -/- Ropy 0.72
VTM3R37T - - - + ~ +B/+B Ropy 0.41
Streptococcus gallolyticus subsp. ruminantium subsp. nov.
VTM1R53 + - + + + -/- NR n/a
VTM4R54T + - + + + -/- Ropy 0.63
Total (+)
isolates 31 15 28 34
25
15
29
192
Table 6-2 Acid production and ability of isolates to produce an acid byproduct from a variety of
carbohydrates. Acid production in skim milk was measured as pH over time. Positive acid production results (+) were
indicated by a color change. All isolates produced acid from D-fructose, galactose, D+-glucose, glycerol,
lactose, maltose and sucrose (data not shown).
Isolate Acid production
(pH) Acid production from carbohydrates
6hr 24hr
N-A
cet
ylg
luco
sam
ine
D-a
rab
inose
Cel
lob
iose
Cel
lulo
se
Gly
cogen
Inu
lin
D-M
an
nose
Mel
ibio
se
D-r
aff
inose
Sali
cin
Streptococcus gallolyticus subsp. gallolyticus
VTM3R11 5.83 4.72 + + + - + + + + + +
VTM3R12 6.14 5.11 + + + + + + + + + +
VTM4R13 6.35 5.34 + + + + + + + + + +
VTM1R14 6.13 5.11 + + + + + + + + + +
VTM3R17 6.11 5.38 + + + - + + + + + +
VTM4R20 5.95 4.70 + + + + + + + + + +
VTM3R21 6.15 5.07 + + + + + + + + + +
VTM3R22 5.88 4.69 + + + + + + + + + +
VTM3R24 5.91 4.71 + + + - + + + + + +
VTM1R25 6.04 4.84 + + + + + + + + + +
VTM3R26 6.12 5.12 + + + + + + + + + +
VTM1R27 5.57 4.25 + + + - + + + + + +
VTM1R29 5.95 4.61 + + + + + + + + + +
VTM3R32 6.01 4.96 + + + + + + + + + +
VTM1R35 6.13 4.92 + + + - + + + + + +
VTM1R38 6.25 4.80 + + + + + + + + + +
VTM1R41 5.84 4.47 + + + + + + + + + +
VTM3R42 5.79 4.84 + + + + + + + + + +
VTM2R45 6.07 4.74 + + + + + + + + + +
VTM4R46 6.05 5.57 + + + - + + + + + +
VTM2R47 5.97 4.44 + + + - + + + + + +
VTM1R48 5.91 4.61 + + + - + + + + + +
193
VTM1R50 6.08 5.52 - + + + + + + + + +
VTM2R55 5.88 4.82 + + + - + + + + + +
Streptococcus gallolyticus subsp. macedonicus
VTM1R33 6.07 4.98 - - - - - - - - - -
VTM2R39 5.88 4.57 - + - - - - - - - -
VTM4R51 6.08 5.52 + + - - - - - - - -
Streptococcus alcis sp. nov.
VTM1R28T 5.88 4.64 + + + + + + + + + +
Streptococcus vermontensis sp. nov.
VTM3R19T 6.11 5.09 + + + - - - + + - +
Streptococcus gallolyticus subsp. mannosilyticus subsp. nov.
VTM3R15 6.18 5.85 + - - - - - + - - -
VTM1R31T 5.96 4.61 - + - - - - + - - +
VTM1R44 6.08 5.30 - - - - - - + - - -
VTM4R49 6.10 4.56 + - + - - - + - - +
Streptococcus gallolyticus subsp. melibiosilyticus subsp. nov.
VTM3R23 5.98 5.08 - + + + - - + + - +
VTM3R37T 6.06 5.85 + + + + - - + + - +
Streptococcus gallolyticus subsp. ruminantium subsp. nov.
VTM1R53 6.22 6.21 - + - - - - - - - -
VTM4R54T 6.14 5.67 - + - + - - - + - -
Total (+) isolates 29 33 29 19 25 25 32 29 25 30
194
Table 6-3 G+C content of isolates and DNA-DNA hybridization to reference strains Streptococcus
gallolyticus gallolyticus (ATCC 700065) and S. gallolyticus macedonicus (ATCC BAA-249).
DNA-DNA hybridization (DDH) was calculated based on ΔTm between reference and hybrid strains, and
regression equations generated from previously published DHH data for S. gallolyticus gallolyticus
(R2=0.734) and S. gallolyticus macedonicus (R2=0.481) (Schlegel at el., 2003).
% G+C
Content
S. gallolyticus
gallolyticus
S. gallolyticus
macedonicus
Isolate ΔTm
°C
%
DDH
ΔTm
°C
%
DDH
VTM1R28T S. alcis sp. nov. 38.0 1.0 84.2 1.2 83.0
VTM3R19T S. vermontensis sp. nov. 37.9 1.2 82.2 0.4 90.6
VTM1R31T
S. gallolyticus
mannosilyticus subsp.
nov.
37.9 1.9 77.4 2.6 70.0
VTM3R37T
S. gallolyticus
melibiosilyticus subsp.
nov.
38.1 2.0 76.7 2.0 75.4
VTM1R54T
S. gallolyticus
ruminantium subsp. nov. 38.1 2.4 73.7 1.0 84.9
195
6.12 Supplemental Material
Supplemental Figure 1 Growth of isolates at varying temperatures (A), salinities (B) and pH (C),
measured as absorbance at 600 nm.
196
Supplemental Figure 2 Protein production of ropy-strain isolates, measured as protein precipitate at
750nm. Casein standards were used to generate a standard curve (R2=0.995).
Supplemental Figure 3 Acid production of isolates in skim milk media incubated at 37°C. The pH of
cultures was measured at 1, 6 and 24 hours to determine acid production over time. Initial pH of the
media was calculated using a sterile blank as control.
0.0
0.5
1.0
1.5
2.0
2.5
0 0.5 1 1.5
mg/m
l p
rote
in
Absorbance at 750nm
Casein
Isolates
0
1
2
3
4
5
6
7
1 h 6 h 24 h
pH
Control
197
CHAPTER 7 FIBROLYTIC BACTERIA ISOLATED FROM THE RUMEN
OF NORTH AMERICAN MOOSE (ALCES ALCES).
Suzanne L. Ishaq*,1
, Doug Reis2, and André-Denis G. Wright
1,3
1 Department of Animal Science, College of Agriculture and Life Sciences, University of
Vermont, Burlington, Vermont 05405
2 Department of Microbiology and Molecular Genetics, College of Agriculture and Life
Sciences, University of Vermont, Burlington, Vermont 05405
3 Present address: School of Animal and Comparative Biomedical Sciences, College of
Agriculture and Life Sciences, University of Arizona, Tucson, Arizona 85721
*Suzanne Ishaq, Department of Animal Science, University of Vermont, 203 Terrill
Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-802-656-
8196.
Keywords: Bacillus/bacteria/fibrolytic/moose/probiotic
198
7.1 Abstract
Fibrolytic bacteria were isolated from the rumen of North American moose
(Alces alces), which eat a high-fiber diet of woody browse. Thirty-one isolates were
cultured from moose rumen digesta samples collected in Vermont. Using Sanger
sequencing of the 16S rRNA gene, culturing techniques, and optical densities, isolates
were identified and screened for biochemical properties important to plant carbohydrate
degradation. The 31 isolates had the following percent identities to known sequences in
the NCBI database: Bacillus licheniformis, 98–100% (n=22); B. foraminis, 98% (n=1); B.
firmus, 98% (n=1); B. flexus, 100% (n=1); B. niabensis, 98% (n=1); Paenibacillus
woosongensis, 98% (n=1); and Staphylococcus saprophyticus, 99–100% (n=4). Isolates
were able to digest cellulose (n=31), cellobiose (n=28), xylan (n=26), starch (n=21),
carboxymethylcellulose (n=21), and lignin (n=18) under minimal nutritional conditions.
Fifteen isolates were able to digest all six carbohydrates or plant components tested.
Isolates were able to tolerate up to 10% (n=16) salinity, between pH 4.0 (n=27) and pH
10.0 (n=27), and between 20°C (n=28) and 55°C (n=30). Isolates were tolerant to
sodium azide (n=30), could reduce potassium tellurite (n=3), metabolize mannitol (n=29),
produce indole from tryptophan (n=4), and all isolates could use citrate or propionate as a
sole carbon source, as well as ammonium ions for nitrogen.
199
7.2 Introduction
Fibrolytic bacteria in the digestive tract of ruminants are instrumental in the
digestion of plant matter for the host. The North American moose (Alces alces) is a large
cervid, which consumes a high-fiber diet of woody browse: mainly willow, pine, maple,
and fir (Belovsky and Jordan, 1981; Shipley, 2010). They also consume seasonally
available aquatic vegetation, which is higher in sodium that arboreal vegetation
(Belovsky and Jordan, 1981). This diet provides several nutritional challenges for which
the moose has adapted. Moose produce tannin-binding salivary proteins to reduce the
digestibility-reducing effects of tannins (Austin et al., 1989), and have a large liver: body
size which may help them detoxify secondary metabolites found in willow and conifers
(Shipley, 2010). Species of rumen bacteria that are resistant to secondary metabolites
have been identified in some ruminants (Odenyo and Osuji, 1998; Dailey et al., 2008;
Sundset et al., 2008), but have not yet been described in moose.
Few studies have identified the rumen bacteria of moose (Ishaq and Wright,
2012, 2014), or used culturing techniques to isolate bacteria from the rumen of moose
(Dehority, 1986). Previously, it was shown that moose from Vermont contained a higher
proportion of bacteria belonging to the phylum Firmicutes, which are mostly fibrolytic
(Ishaq and Wright, 2014).
200
7.3 Methods
Fresh rumen samples were collected during the October 2010 hunting season in
Vermont, with permission of licensed hunters through the Vermont Department of Fish
and Wildlife. Hunters were given written and verbal instructions to collect samples from
well inside the rumen, and to seal the container quickly to reduce oxygen exposure.
Whole rumen samples (i.e. fluid and particulate matter) collected during field dressing
were frozen within 2 h of death, and were transferred to the laboratory within 24 h, where
they were mixed with an equal volume of 80% glycerol and stored at -80°C until
culturing. Additional information regarding the hosts can be found in Ishaq & Wright
(2012). Isolates were given unique identifiers (i.e. VTM3R11) containing the following
abbreviations: Vermont (VT), moose (M), individual number (1–4), and rumen (R), as
well as isolate number.
Bacteria were isolated on M8 agar plates (Bryant and Robinson, 1961; Dehority
and Grubb, 1976), with an added 2 g/L of cellulose and cellobiose, inside an anaerobic
chamber (COY Laboratories, Michigan, US). Whole rumen contents were serial diluted,
and all dilutions (10-1
to 10-9
) were plated with five replicates. Plates were monitored for
up to 7 d, and colonies were picked and re-isolated on fresh media until colonies were
shown to be pure using gram staining and colony morphology measurements. A total of
31 isolates were cultured from four individual moose rumen samples, and stock aliquots
of each isolate were stored at -80°C. Isolates were tested for their catalase reaction
(Gordon et al., 1973).
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Monocultures were identified using automated cycle sequencing at the
University of Vermont DNA Analysis Facility. The bacterial 16S rRNA gene was
amplified using the universal bacterial primers 27F and 1494R (Lane, 1991). PCR was
performed using the iTaq DNA Polymerase kit (Bio-Rad, California, US) following the
manufacturer’s instructions. PCR conditions were: initial denaturation of 94°C for 5 min,
then 33 cycles of 94°C for 30 s, 50°C for 30 s, and 72°C for 1 min, followed by a final
extension of 72°C for 6 min. PCR was performed on a C1000 thermal cycler (Bio-Rad,
California, US). Recalcitrant isolates were first extracted using the DNA extraction
protocol in the QIAamp DNA Stool Mini Kit (QIAGEN, Maryland, USA). Sequences
were proofread using ChromasPro ver. 1.7.5, and aligned using the CLUSTALW
algorithm in MEGA ver. 6.0. The alignment was visually inspected, and then used to
calculate pairwise genetic distance using the Kimura 2-parameter model (Tamura et al.,
2011). Sequences were classified using BLAST (NCBI) and compared to published
sequences of fibrolytic bacteria from NCBI, and a neighbor joining tree was generated
using MEGA.
As cellulose in the broth media prevented accurate optical density
measurements, isolates were subcultured into 10 ml of tryptic soy broth (TSB) (1%
vol/vol inoculation), and then incubated for 24 h at various temperatures or pH (adjusted
prior to autoclaving). Optical density was used to determine relative growth using a
Spectronic 200 (ThermoScientific, California, US), with absorbance measured 600 nm
(Georgalaki et al., 2002). All samples were run in triplicate, and optimal ranges were set
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as all isolates measuring >0.5% absorbance. Optimal salinity was measured as growth on
tryptic soy agar (TSA) media with 4-15% NaCl. Heat tolerance was tested by immersing
48 h old cultures in a 60°C water bath for 30 min, then inoculating TSA plates (1%
vol/vol inoculation) and incubating at 37°C for up to 72 h to observe for growth. Isolates
which were able to survive >55°C were tested for their ability to tolerate sodium azide.
Isolates were grown on azide dextrose media (tryptone, 15g/L; beef extract, 4.5g/L;
glucose, 7.5g/L; sodium chloride, 7.5g/L; and sodium azide, 0.2g/L; pH 7.2) and
incubated at 45°C for 5 d and observed for growth.
Isolates were tested for their ability to digest complex carbohydrates (cellulose,
cellobiose, carboxymethylcellulose, xylan, and starch) or plant components (lignin) on
minimal media (Bandounas et al., 2011). Minimal media plates were incubated at 37°C
for up to two weeks to observe for growth. Isolates were tested on mannitol media for
their ability to metabolize mannitol and tolerate potassium tellurite. To test for the
production of the aromatic compound indole from the amino acid tryptophan, isolates
were grown in 1% w/v tryptone broth for 14 d, after which Kovac’s reagent was added to
the culture broth to test for a color reaction (Kovacs, 1928). Isolates were subcultured
into Simmon’s Citrate slants (Simmons, 1926) and Propionate Slants (Gordon et al.,
1973) for 7 d, and observed for bacterial growth and color change to indicate the ability
to use citrate or propionate, respectively, as a carbon source and ammonia as a nitrogen
source (Georgalaki et al., 2000). To test the ability to reduce nitrate to nitrite, isolates
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were subcultured into nitrate broth for 2 and 7 d and then tested for color change using
potassium iodine strips moistened with 1N HCl.
7.4 Results
All 31 isolates were gram positive and catalase positive. Isolates had the
following percent identity to known sequences in NCBI: Bacillus licheniformis, 98–
100% (n=22); B. foraminis, 98% (n=1); B. firmus, 98% (n=1); B. flexus, 100% (n=1); B.
niabensis, 98% (n=1); Paenibacillus woosongensis, 98% (n=1); and Staphylococcus
saprophyticus, 99–100% (n=4) (Table 1, Figure 1). All 16S rRNA sequences are
available from NCBI (KP245773- KP245803).
All 31 isolates tolerated 4% NaCl (data not shown). Isolates (n=16) were able to
tolerate up to 10% salinity (Table 1), including B. firmus, B. flexus, some B.
licheniformis, B. niabensis, P. woosongensis, and some S. saprophyticus. Isolates from
all species grew to >0.5 absorbance between pH 4.0 (n=27) and pH 10.0 (n=27), and
between 20°C (n=28) and 55°C (n=30) (Figure 2). Twenty-nine isolates exhibited
excellent growth after heat shock, but two isolates (B. niabensis VTM4R58, and S.
saprophyticus VTM2R99) exhibited no growth. All but one B. licheniformis isolate
(VTM3R64) tolerated sodium azide and exhibited growth after 5 d.
Under minimal conditions, isolates were able to digest cellobiose (n=28), xylan
(n=26), starch (n=21), carboxymethylcellulose (n=21), and lignin (n=18) (Table 1). All
31 isolates were able to grow on cellulose, glucose, and lactose (data not shown), and 15
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isolates were able to digest all six carbohydrates tested (Table 1). Twenty-seven isolates
were able to metabolize mannitol and produce a color change, but four B. licheniformis
could not (VTM2R66, VTM1R71, VTM1R80, VTM1R88). Only two B. licheniformis
isolates (VTM2R66, VTM2R82) and one B. foraminis isolate (VTM4R85) could reduce
tellurite. Two B. licheniformis isolates (VTM1R74, VTM1R75), one B. firmus isolate
(VTM2R84), and one B. foraminis isolate (VTM4R85) were able to produce indole from
tryptophan. All isolates were able to use citrate and propionate as their carbon source,
and use ammonia for nitrogen. Twelve isolates were able to reduce nitrite to nitrate after
48 h, and an additional two isolates (S. saprophyticus VTM2R99 and B. firmus
VTM2R84) were able to reduce nitrite to nitrate after 7 d of growth (Table 1).
7.5 Discussion
Thirty-one fibrolytic bacterial isolates were examined for their biochemical
capabilities and potential as a probiotic for ruminants. Based on their ability to survive a
wide range of growth parameters and digest complex carbohydrates even on minimal
media, many of the thirty-one fibrolytic isolates in the present study have the potential for
use in agricultural or industrial applications. However, the ability to survive in the
developing digestive tract using milk or milk replacer as a substrate, as well as the ability
to consistently grow well in culture, are also important considerations for a viable
probiotic product.
205
Bacillus licheniformis is an important member of the rumen community as it
produces a variety of extracellular enzymes which can digest lignocelluloses (Archana
and Satyanarayana, 1997), starches (Saito, 1973; Pen et al., 1992), keratin (Lin et al.,
1992), and acetate (Veith et al., 2004). It is able to digest glucose anaerobically (Veith et
al., 2004), and certain strains show antibiotic resistance (Pollock, 1965; Moews et al.,
1990). The industrial applications of B. licheniformis are extensive due to the breadth of
its enzymatic products, but also because many are thermophilic or halophilic (Gordon et
al., 1973; Veith et al., 2004; Wei et al., 2010). The present study identified 22 isolates
which had greater than 98% sequence identity to B. licheniformis, as well as four isolates,
which had greater than 98% sequence identity to B. foraminis, B. firmus, B. flexus, and B.
niabensis.
Staphylococcus saprophyticus is a cellulolytic bacterium originally isolated from
the termite gut (Paul et al., 1986). The present study identified four isolates which had
greater than 99% sequence identity to S. saprophyticus. Paenibacillus woosongensis was
originally isolated from forest soil, and was shown to digest a variety of carbohydrates,
including cellulose and xylan (Lee and Yoon, 2008). One isolate in the present study had
a 98% sequence identity to P. woosongensis.
The present study found that 15 out of 31 isolates were able to digest all six
different carbohydrates and plant components investigated on minimal media. Lignin is
an aromatic alcohol polymer found in the cell walls of plants and some algae. In the cell
wall it is often bonded to cellulose or hemicelluloses, which increases the durability of
206
plants cell walls, but decreases their digestibility. After cellulose, lignin is the second
most abundant polymer on Earth. Xylans are hemicelluloses which are found in the cell
wall of plants, especially hardwoods, and some algae, and if it is not fermented by gut
microorganisms it can decrease the absorption of minerals in the intestines (Jiang K,
1986). Mannitol is a sugar found in species of deciduous flowering ash.
Carboxymethylcellulose is a purified form of cellulose that is more soluble in water, thus
it in used in food production, pharmaceuticals, or industrial applications.
The ability to survive under restrictive nutritional conditions is especially
important trait for bacteria used in industrial applications, but can also provide an
advantage over competitive species or strains of bacteria which require vitamins or other
substrates in the rumen. Additionally, bacteria which can positively impact the host,
would be beneficial to overall animal health in addition to increasing dietary efficiency.
Indole production often takes place in the intestines, and is used as a quorum-sensing
signal molecule between gut bacteria. However, its presence in the intestines also
stimulates cellular junction-associated molecules in gut epithelial cells, and promotes
resistance to dextran sodium sulfate (DSS)-induced colitis (Shimada et al., 2013).
7.6 References
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207
3. Austin PJ, Suchar LA, Robbins CT, Hagerman AE: Tannin-binding proteins in
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4. Odenyo AA, Osuji PO: Tannin-tolerant ruminal bacteria from East African
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7. Ishaq SL, Wright A-DG: High-throughput DNA sequencing of the ruminal
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8. Ishaq SL, Wright A-DG: Insight into the bacterial gut microbiome of the North
American moose (Alces alces). BMC Microbiol 2012, 12:212.
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ruminants Proc Sixth Int Symp Rumin Physiol. Edited by Milligan LP, Grovum WL,
Dobson A. Englewood Cliffs: Prentice-Hall; 1986:307–325.
10. Dehority BA, Grubb JA: Basal medium for the selective enumeration of rumen
bacteria utilizing specific energy sources. Appl Env Microbiol 1976, 32:703–710.
11. Bryant MP, Robinson IM: An improved nonselective culture medium for ruminal
bacteria and its use in determining diurnal variation in numbers of bacteria in the
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12. Gordon RE, Pang CH-N, Haynes WC: The Genus Bacillus. Washington: Agricultural
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13. Lane DJ: 16S/23S rRNA sequencing. In Nucleic acid Tech Bact Syst. Edited by
Stackebrandt E, Goodfellow M. New York City: John Wiley and Sons; 1991:115–175.
14. Tamura K, Peterson D, Peterson N, Stecher G, Nei M, Kumar S: MEGA5:
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15. Georgalaki MD, Van Den Berghe E, Kritikos D, Devreese B, Van Beeumen J,
Kalantzopoulos G, De Vuyst L, Tsakalidou E: Macedocin, a food-grade lantibiotic
produced by Streptococcus macedonicus ACA-DC 198. Appl Env Microbiol 2002,
68:5891–5903.
16. Bandounas L, Wierckx NJ, de Winde JH, Ruijssenaars HJ: Isolation and
characterization of novel bacterial strains exhibiting ligninolytic potential. BMC
Biotechnol 2011, 11:94.
17. Kovacs N: Eine vereinfachte Methode zum Nachwei s der Indolbildung durch
Bakterien. Z Immunitats Forsch Exp Ther 1928, 55:311.
18. Simmons JS: A culture medium for differentiating organisms of typhoid-colon
aerogenes groups and for isolation of certain fungi. J Infec Dis 1926, 39:209.
19. Georgalaki MD, Sarantinopoulos P, Ferreira ES, De Vuyst L, Kalantzopoulos G,
Tsakalidou E: Biochemical properties of Streptococcus macedonicus strains isolated
from Greek Kasseri cheese. J Appl Microbiol 2000, 88:817–825.
20. Archana A, Satyanarayana T: Xylanase production by thermophilic Bacillus
licheniformis A99 in solid-state fermentation. Enzym Microb Tech 1997, 21:12–17.
21. Pen J, Molendijk L, Quax WJ, Sijmons PC, van Ooyen AJJ, van den Elzen PJM,
Rietveld K, Hoekema A: Production of active Bacillus licheniformis alpha-amylase in
tobacco and its application in starch liquefaction. Bio/Technology 1992, 10:292–296.
22. Saito N: A thermophilic extracellular α-amylase from Bacillus licheniformis. Arch
Biochem Biophys 1973, 155:290–298.
23. Lin X, Lee C-G, Casale ES, Shih JCH: Purification and characterization of a
keratinase from a feather-degrading Bacillus licheniformis strain. Appl Env
Microbiol 1992, 58:3271–3275.
24. Veith B, Herzberg C, Steckel S, Feesche J, Maurer KH, Ehrenreich P, Bäumer S,
Henne A, Liesegang H, Merkl R, Ehrenreich A, Gottschalk G: The complete genome
sequence of Bacillus licheniformis DSM13, an organism with great industrial
potential. J Mol Microbiol Biotech 2004, 7:204–211.
25. Moews PC, Knox JR, Dideberg O, Charlier P, Frère JM: Beta-lactamase of Bacillus
licheniformis 749/C at 2 A resolution. Proteins 1990, 7:156–71.
209
26. Pollock MR: Purification and properties of penicillinases from two strains of
Bacillus licheniformis: a chemical, physiochemical and physiological comparison. Biochem J 1965, 94:666–75.
27. Wei X, Ji Z, Chen S: Isolation of halotolerant Bacillus licheniformis WX-02 and
regulatory effects of sodium chloride on yield and molecular sizes of poly-gamma-
glutamic acid. Appl Biochem Biotechnol 2010, 160:1332–40.
28. Paul J, Sarkar A, Varma AK: In vitro studies of cellulose digesting properties of
Staphylococcus saprophyticus isolated from termite gut. Curr Sci 1986, 55:710–714.
29. Lee J-C, Yoon K-H: Paenibacillus woosongensis sp. nov., a xylanolytic bacterium
isolated from forest soil. IJSEM 2008, 58:612–616.
30. Jiang K S: Effects of dietary cellulose and xylan on absorption and tissue
contents of zinc and copper in rats. J Nutr 1986, 116:999–1006.
31. Shimada Y, Kinoshita M, Harada K, Mizutani M, Masahata K, Kayama H, Takeda K:
Commensal bacteria-dependent indole production enhances epithelial barrier
function in the colon. PLoS One 2013, 8:e80604.
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7.7 Figures
Figure 7-1 Phylogenetic comparison of 31 isolates which known sequences (NCBI).
A neighbor-joining tree was created using MEGA ver. 6 and the Kimura 2-paramter
model.
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Figure 7-2 Growth at various temperatures (A) and pHs (B), as measured by optical density at 600
nm.
212
7.8 Tables
Table 7-1 Isolate GenBank ID, closest GenBank match with percent identity, growth on minimal
media or on high salinity, and ability to reduce nitrite.
Isolate GenBank
ID
Closest GenBank
Identification
CM
C
Cel
lob
iose
Lig
nin
Sta
rch
Xy
lan
8%
Na
Cl
10
% N
aC
l
Nit
rate
red
uct
ion
VTM4R85 KP245773 98% B. foraminis + + + + + - - -
VTM2R84 KP245774 98% B. firmus + + + + + + + +
VTM1R86 KP245775 100% B. flexus + + - + + + + +
VTM4R61 KP245776 99% B. licheniformis + + + + + + + +
VTM1R62 KP245777 99% B. licheniformis + + + - + + + -
VTM4R63 KP245778 99% B. licheniformis - + - + + + + -
VTM3R64 KP245779 99% B. licheniformis + + + + + + + +
VTM1R65 KP245780 98% B. licheniformis + + + + + + + -
VTM2R66 KP245781 99% B. licheniformis + + + + + + - -
VTM2R67 KP245782 100% B. licheniformis - + - - + - - -
VTM4R68 KP245783 98% B. licheniformis - + + + + + + +
VTM4R69 KP245784 99% B. licheniformis + + + + + + + +
VTM4R70 KP245785 99% B. licheniformis - + - - + - - -
VTM1R71 KP245786 99% B. licheniformis + + - + + + - +
VTM1R72 KP245787 99% B. licheniformis - + - - - + + -
VTM2R73 KP245788 99% B. licheniformis + + - + + - - +
VTM1R74 KP245789 99% B. licheniformis + + + + + + + +
VTM1R75 KP245790 99% B. licheniformis - - - - - - - -
VTM3R76 KP245791 99% B. licheniformis + + + + + + + -
VTM3R77 KP245792 99% B. licheniformis - + + - - - - -
VTM3R78 KP245793 99% B. licheniformis - - + - + - - -
VTM1R80 KP245794 99% B. licheniformis + + - + + - - +
VTM2R81 KP245795 99% B. licheniformis - - - - - - - -
VTM2R82 KP245796 99% B. licheniformis + + + + + + - +
VTM1R88 KP245797 99% B. licheniformis + + - + + - - +
VTM4R58 KP245798 98% B. niabensis + + + - + + + -
VTM1R92 KP245799 98% P. woosongensis + + + + + + + +
VTM1R96 KP245800 100% S. saprophyticus bovis + + + + + + + -
VTM4R98 KP245802 100% S. saprophyticus bovis + + + + + + + -
VTM4R97 KP245801 99% S. saprophyticus s, - + - - - - - -
VTM2R99 KP245803 99% S. saprophyticus s. + + - + + - - +
Total positive (n=31) 21 28 18 21 26 19 16 14
B = Bacillus; P = Paenibacillus; S = Staphylococcus
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CHAPTER 8 THE EFFECTS OF ADMINISTERING A FIBROLYTIC
PROBIOTIC MADE FROM MOOSE RUMEN BACTERIA TO NEONATAL
LAMBS.
Suzanne L. Ishaq1*, Christina J. Kim
1, and André-Denis G. Wright
1,2
1
Department of Animal Science, College of Agriculture and Life Sciences, University of
Vermont, 570 Main St., Burlington, Vermont 05405
2 Present address: School of Animal and Comparative Biomedical Sciences, College of
Agriculture and Life Sciences, University of Arizona, Tucson, Arizona 85721
* Suzanne Ishaq, Department of Animal Science, University of Vermont, 203 Terrill
Building, 570 Main Street, Burlington VT 05405. slpelleg@uvm.edu. Fax) 1-802-656-
8196.
Keywords/Cross-reference: 16S rRNA gene, lambs, moose, probiotic
214
8.1 Abstract
The present study investigated the effect of a fibrolytic probiotic, using bacteria isolated
from the rumen of the North American moose (Alces alces), and which was administered
daily to neonate lambs until 1 week after weaning. It was hypothesized that regular
administration of a fibrolytic probiotic to neonate animals through weaning would
increase the developing rumen bacterial diversity, increase animal production, and allow
for long-term colonization of the probiotic species. Neither weight gain nor wool quality
was improved in lambs given a probiotic, but dietary efficiency was increased as
evidenced by the reduced feed intake (and rearing costs) without a loss to weight gain.
Additionally, the probiotic lambs had a lower acetate to propionate ratio than control
lambs, which has previously been shown to indicate increased dietary efficiency.
Sampling coverage was high in the first two time points, after which it decreased.
Conversely, Shannon, Inverse Simpson, CHAO, and ACE were low and increased over
time, all of which is a function of the increasing diversity of the rumen microbiota as the
rumen develops. The experimental group had a higher diversity at the beginning of the
experiment. Fibrolytic bacteria made up the majority of sequences. In all time points
and both groups, Prevotella was the most prevalent genus, while Butyrivibrio and
Ruminococcus were also prevalent. While protozoal densities increased over time and
were stable, methanogen densities varied greatly in the first six months of life for lambs.
This is likely due to the changing diet and bacterial populations in the rumen.
215
8.2 Introduction
Over the first few months of life, the rumen microbiome of the neonate ruminant
undergoes rapid shifts as the animal weans and changes diets, and the rumen develops.
As the rumen develops, it increases in size until it is the largest stomach chamber, its
rumen papillae become longer and more differentiated, and a stable microbiota is
established. Initially, lactic acid bacteria (LAB), such as Streptococcus thermophilus,
Lactobacillus acidophilus, or Bifidobacterium bifidus, tend to dominate, as well as
Escherichia coli (Fonty et al., 1987; Minato et al., 1992). While cellulolytic bacteria do
appear in the rumen within the first few days of life (Fonty et al., 1987; Minato et al.,
1992; Morvan et al., 1994), it is not until weaning and a transition to a plant-based diet
that they become the dominant type of rumen bacteria (Sinha and Ranganathan, 1983;
Ishaq and Wright, 2014). As the microbial diversity adapts to the rumen environment
and the diet provided, so, too, do the gastrointestinal tract epithelia adapt to the
microbiota. Host cells can eventually recognize conserved cell-surface microbial
markers, and the presence of these will active pro- or anti-inflammatory responses, as
well as host epithelial cell signaling (Chang, 2008; Abreu, 2010). Thus, introducing new
microbiota after these host-microbiota interactions have been made may not be
successful.
Different weaning practices can influence the developing microbiota. Including a creep
feed or hay along with a milk diet can encourage larger populations of fibrolytic bacteria
216
(Yáñez-Ruiz et al., 2010), improve starch and fiber digestion (Poe et al., 1971), increase
volatile fatty acid production (especially acetate and butyrate) (Laarman et al., 2012), and
improve rumen development (Norouzian et al., 2011). Likewise, development of the
rumen microbiota can be encouraged through early colonization by administering a
probiotic. Probiotics for livestock are generally comprised of LAB or fibrolytic bacteria.
LAB probiotics are more common in pre-weaned ruminants (Abe et al., 1995; Vlková et
al., 2010; Ripamonti et al., 2011) or monogastrics (Abe et al., 1995; Pajarillo et al.,
2015), but are also used in adult ruminants (Aikman et al., 2011; Boyd et al., 2011).
Fibrolytic probiotics have more often been used to improve digestive function in adult
ruminants (Kumar and Sirohi, 2013; Præsteng et al., 2013), as well as for pre-weaned
ruminants (Sun et al., 2010). Many studies report short-term beneficial effects only,
either due to the production animals reaching market weight, or because the probiotic
failed to colonize the digestive tract long-term.
It was hypothesized that regular administration of a fibrolytic probiotic to neonate
animals through weaning would increase the developing rumen bacterial diversity,
increase animal production, and allow for long-term colonization of the probiotic species.
The present study investigated the effect of a fibrolytic probiotic, which had been created
using bacteria isolated from the rumen of the North American moose (Alces alces), and
which was administered daily to neonate lambs until 1 week after weaning at 9 weeks of
age. Neonatal ruminants undergo rumen development over a period of 8-12 weeks,
217
during which the rumen and reticulum increase in size and functionality (Hobson and
Fonty, 1997), making the weaning period an ideal time period for rumen manipulation.
Moose were chosen as the source for probiotic strains as they are highly likely to host
efficient species or strains of bacteria, which can digest cellulose, hemicellulose, and
lignin. Moose subsist on a diet of woody browse which is very high in fiber (Belovsky,
1981; Molvar et al., 1993; Routledge and Roese, 2004). Additionally, their body
temperature and dry matter intake is more similar to lambs than to calves or goat kids,
thus improving the likelihood of long-term rumen colonization by the species of interest
(Gasaway and Coady, 1974; Franzmann et al., 1984; Piccione et al., 2003; Dwyer and
Morgan, 2006; Committee on the Nutrient Requirements of Small Ruminants, 2007;
Kochan, 2007; Piccione et al., 2007).
8.3 Methods
All procedures were approved by the UVM Institutional Animal Care and Use
Committee (protocol (14-008). Results are presented by date and experimental week
(week).
Twenty Dorset-cross lambs, 4-7 days of age, were purchased from Bonnieview Farm,
Craftsbury, VT. Lambs were group housed at the Miller Research Farm at the University
of Vermont (UVM), Burlington VT, beginning on April 22, 2014. Eighteen male and
218
two female lambs were randomly assigned to either the Control (n=10) or the
Experimental (n=10) group with nine males and one female per group. Males were
castrated within the first two weeks of the study, and groups had similar weights (mean
5.9±0.2 kg) prior to the beginning of the study. Water was provided ad libitum. For four
weeks, lambs were fed DuMOR lamb milk replacer (Tractor Supply Co, Shelburne VT)
using bucket feeding systems (Premier 1 Supplies, Washington, IO), and group intake
was recorded. Beginning in week five, lambs were also given DuMOR sheep starter
pelleted grain feed (Tractor Supply Co, Shelburne VT), and group intakes were recoded.
At week six, lambs were weaned off of the milk replacer and were fed grain pellets and
timothy hay, and again group intake was recorded. At eight weeks (June 26, 2014) lambs
were transferred to Sterling College in Craftsbury, VT, where they were maintained as a
single mob grazing on pasture until mid-October, 2014.
8.3.1 Probiotic
Five bacterial isolates were chosen for use as a probiotic based on a previous study
(Ishaq, Reis, et al., 2015). Isolates are as follows, with GenBank accessions numbers in
parentheses: Bacillus foraminis VTM4R85 (KP245773), B. firmus VTM2R84
(KP245774), B. licheniformis VTM2R66 (KP245781), B. licheniformis VTM1R74
(KP245789), and Staphylococcus saprophyticus bovis VTM1R96 (KP245800). Isolates
were selected based on their ability to digest carboxymethylcellulose, cellobiose,
219
cellulose, lignin, starch, and xylan on minimal media. Isolates were also able to survive
at a wide range of temperatures, salinities, and pH.
Isolates were cultured separately in M8+cellulose broth for approximately six months to
determine whether the isolate could be maintained for an extended period at sufficient
concentrations to be used as a probiotic. Purity was determined via weekly gram
staining, and occasional Sanger sequencing as previously described (Ishaq, Reis, et al.,
2015). Concentration was measured by number of colony forming units (CFUs) on a
plate count, performed in duplicate. As per Food and Drug Administration (FDA)
regulations, probiotics must maintain 107 CFUs for the duration of its shelf life. The five
isolates were then tested for their ability to survive in commercial milk replacer for up to
72 hr at 37°C, and maintain a minimum density of 107. Isolates were cultured for 24, 48
and 72 hr in DuMOR Blue Ribbon lamb milk replacer (DuMOR 06-9551-0234),
reconstituted according to manufacturer instructions, and then replated on M8+cellulose
for plate counts at 24 hr.
Isolates were grown individually in M8 broth supplemented with cellulose as previously
described (Ishaq, Reis, et al., 2015). Cultures were checked regularly for purity using
gram staining, and concentrations were measured using standard plate counts. Twenty-
four hour old cultures were combined at equal concentration within 1 hour of
administration and kept cool during transport. One ml of inoculant or blank media was
220
administered orally to experimental and control lambs, respectively, daily between noon
and 1 pm. After two weeks, when lambs were approximately 20 days old, the dose was
increased to 2 ml/day. Probiotic or blank media was given daily for 9 weeks until
weaning at 9.5 to 10 weeks of age.
8.3.2 Production
Lambs were weighed every 2-3 days for the first three weeks, then weekly through
weaning, then monthly for the duration of the study. At study week 8, when lambs were
weaned and put on pasture, a 2 x 2 in patch was shaved on the side, within 3-5 in of the
spine (i.e. mid-side sample). Wool was allowed to grow out for 14 weeks, after which a
1 x 1 in patch was shaved, dried, weighed, and sent for fiber testing to Yocom-McColl
Testing Labs in Denver, CO. Significance for this and other measurements was
calculated using Student’s T-test, and deviation is presented as standard deviation (SD) or
standard error mean (SEM).
8.3.3 Rumen sampling
Rumen samples were collected weekly for eight weeks, then monthly once lambs were on
pasture. Samples were collected in the morning, prior to weaning this was within one to
two hours of feeding. Esophageal tubing was used to obtain samples directly from the
rumen, from which up to 15 ml of fluid and particulate matter (ruminal contents) were
collected and put on ice immediately. Some rumen fluid was separated out and used to
221
measure pH and volatile fatty acids. Rumen pH was tested using a MW101 pH meter
(Milwaukee, NC). Volatile fatty acids were measured using gas chromatography at the
William H. Miner Agricultural Research Institute (Chazy, NY). Thawed rumen samples
were centrifuged for 20 min at 4° at 10,000 x G. Supernatant was filtered through a
single layer of Whatman filter paper, and 0.8 ml of filtrate was mixed with an equal
volume of internal standards (oxalic acid and trimethylamine).
8.3.4 Sequencing and DNA data analysis
DNA was extracted from individual samples using the QIAamp DNA stool fast kit
(QIAGEN, MD), and the V1-V3 region of the 16S rRNA gene was amplified using
previously described protocols (Ishaq and Wright, 2014). Amplicons were sent to
Molecular Research, LP (MR DNA) in Shallowater, TX for MiSeq ver. 4.
Sequences were analyzed using MOTHUR ver. 1.31 (Schloss et al., 2009; Kozich et al.,
2013). Sequences were trimmed to remove barcodes and primers, as well as any
sequence that contained a mismatch in the barcode, more than two mismatches in the
primer, sequences with homopolymers >8, sequences < 475 bases or >570 bases, and
sequences with an average quality score <32 over 5 bases. Sequences were aligned to the
Silva 16S rRNA bacteria MOTHUR reference file, which had been modified to include
fibrolytic isolates cultured in the laboratory, including the five which were used in the
probiotic. The reference alignment was also trimmed to begin at 27F and end after 800
222
bases. Chimeras were identified using UCHIME (Edgar et al., 2011) and removed.
Sequences were identified using the k nearest neighbor method. Data were subsampled
to 10,000 sequences per sample, clustered using the nearest neighbor method, and
diversity parameters were measured. ACE (Chao and Shen, 2003), CHAO (Chao and
Shen, 2010), Good’s Coverage (Good, 1953), Shannon-Weiner diversity (Shannon and
Weaver, 1949), AMOVA and Unifrac values are presented as group mean.
In order to compare control and experimental groups from all four time points, sequences
which passed QA were pooled, and were subsampled to 2,000 sequences per sample,
giving 20,000 per group per time point. This subsample was used to create a neighbor-
joining tree using the mother-integrated algorithms for Clearcut (Evans et al., 2006),
linear discriminant analysis (LDA) using the mother-integrated Lefse (Segata et al.,
2011), and principal component analysis (PCoA).
8.3.5 Real-time PCR
Real-time PCR was used to calculate archaeal and protozoal densities in whole samples.
DNA was amplified using a CFX96 Real-Time System (Bio-Rad, CA) and a C1000
ThermalCycler (Bio-Rad, CA). Data were analyzed using CFX Manager Software ver.
1.6 (Bio-Rad, CA). The iQ SYBR Green Supermix kit (Bio-Rad, CA) was used: 12.5µL
of mix, 2.5µl of each primer (40mM), 6.5µL of ddH2O, and 1µL of the initial DNA
extract diluted to approximately 10 ng/μL. For methanogens, the primers targeted the
223
methyl coenzyme-M reductase A gene (mcrA), following the protocol by Denman et al.
(2007). The internal standards for methanogens were a mix of Methanobrevibacter
smithii, M. gottschalkii, M. ruminantium and M. millerae (R2=0.998). For protozoa, the
primers, PSSU316F and PSSU539R (Sylvester et al., 2004), targeted the 18S rRNA gene,
following the protocol by Sylvester et al. (2004), and The internal standards for protozoa
were created in the laboratory using fresh rumen contents as previously described (Ishaq
et al., unpublished). Both protocols were followed by a melt curve, with a temperature
increase 0.5°C every 10s from 65ºC up to 95°C to check for contamination.
8.4 Results
8.4.1 Probiotic
Five isolates (VTM2R66, VTM1R74, VTM2R84, VTM4R85, VTM1R96), which were
selected for further testing, maintained concentrations ranging from 107 to 10
10 CFUs
over six months. The same five isolates were able to maintain densities greater than 107
in liquid lamb replacer over 72 hours.
8.4.2 Production
Total group weight was higher in the control group for nearly the duration of the study,
with the exception of the week 8 weighing; however, this time point was the only one
which came close to statistical significance (p=0.06). The total cost at the end of
weaning (week 8) of milk replacer, starter grain, and timothy hay for the experimental
224
groups was $1564.63, at a weaning weight of 248.95 kg for the group. This gives a yield
of 6.28 $/kg. The total cost of the control group was $1592.17, and at a weaning weight
of 263.25 kg this yields 6.05 $/kg. When taking into account the total group weights at
market weight (aged six months, week 23), the cost/group drops to 6.08 $/kg for the
experimental group and increases to 6.19 $/kg for the control group.
Mid-side sample wool weight was higher (p=0.02) in the experimental group (mean=0.83
g, SEM=0.5) than in the control group (mean=0.67 g, SEM=0.07). Mean fiber diameter
(MFD) was not significantly different (p=0.14) between experimental (MFD=34µ,
SEM=0.6, SD=7.4) and control (MFD=33.1µ, SEM=0.6, SD=7.7) groups. The
experimental group did have a significantly (p=0.04) lower coefficient of variation
(CoV=21.8) than the control group (CoV=23.4). Although the experimental group had a
higher percentage of fibers that were >30µm (66.8%, SEM=3.4 experimental, 62.1%,
SEM=2.7 control), this was not statistically significant (p=0.11).
The average pH over the course of the experiment was 7.2 for the experimental group and
7.0 for the control group (Figure 2). The experimental group had a higher average pH for
the first seven weeks of the experiment and lower variability within the group, while the
control group were more likely to have a higher average for the remainder of the study.
Seven out of 12 sampling time points were significantly different (Figure 2).
225
Total volatile fatty acids were not significantly different between Experimental and
Control lambs (Figure 3); however, groups were significantly different at weeks 5, 11 and
23 when comparing total VFAs including ethanol. Total VFAs were highest at weeks 8
and 15, and lowest at week 9 after being on a hay only diet for one week (Figure 3).
Acetate, proprionate, and butyrate were significantly (p<0.05) higher in experimental
lambs at weeks 15 and 23, while lambs were on pasture. The acetic acid to propionic
acid ratio was statistically lower in the experimental group at weeks 9, 11 and 15 (Figure
4).
8.4.3 Sequencing
Between 11,000 and 95,000 unique sequences passed quality assurance steps per sample,
giving a total of 500,000 to 1.1 million sequences per data set of 20 samples. At the first
sampling time point, week 2, after administering the probiotic for a week, there was little
statistical difference in rumen diversity between groups, except for AMOVA, and
unweighted and weighted Unifrac (Table 1). At week 6, CHAO, ACE, Shannon, and
Coverage were different between groups, with higher diversity in the experimental
groups. Groups were not statistically different on any diversity measure except for
unweighted Unifrac at week 11 in July, after being on pasture for two weeks (Table 1).
However, by week 23 in October, the control group showed higher diversity according to
Shannon and Inverse Simpson, and groups clustered separately by weighted and
unweighted Unifrac.
226
When comparing all time points together in the smaller subsampled data set, there were
1,787 OTUs identified from the 160,000 sequences, with 88 (4.9%) discriminatory OTUs
with LDA >2 (p<0.05). The number of discriminatory OTUs were as follows: week 2,
five experimental, four control; week 6, five experimental, six control; week 11, 37
experimental, 17 control; and week 23, nine experimental, five control. PCoA graphs
showed a strong clustering of groups by sampling time (Figure 5), but not by treatment
(data not shown), indicating that the change of rumen bacteria over the course of rumen
development is a stronger indicator of variance.
Bacteroidetes was the most prevalent phylum (38-73% of total sequences) in both groups
for the duration of the study, with the exception of the first sampling of the control group
(Figure 6). Firmicutes was the second most prevalent (23-59%). In the control group,
Bacteroidetes increased while Firmicutes decreased for the first three sampling (weeks 2,
6 and 11), while the experimental had a general trend of decreasing Bacteroidetes and
increasing Firmicutes over time. Other prominent phyla tended to peak at one or two
time points, including Actinobacteria and Proteobacteria (week 6), Fibrobacteres (week
11), and Synergistetes (weeks 11, 23).
Major families identified are shown in Figure 6, with families belonging to Bacteroidetes
as shades of blue and members of Firmicutes in shades of green. Prevotellaceae (mostly
227
species Prevotella) was a prominent family in all time points and in both groups, but was
significantly higher in the experimental group at week 2. Lachnospiraceae was also
prominent in all samples, although it was significantly higher in the control group at
week 2. The experimental group had more Ruminococcaceae than the control group at
weeks 2 and 6. There were also families which were prominent in only one time point,
such as Bacteroidaceae, Streptococcaceae, and the candidate family p-2534-18B5 in
week 2; Coriobacteriaceae (mostly species Olsenella) in week 6, Fibrobacteraceae in
week 11, and the candidate Family XI of the class Bacilli (phylum Firmicutes) in week
23.
While the genera Bacillus and Staphylococcus were found in both groups at all time
points, there was not enough resolution in the sequencing amplicons to accurately
identify probiotic sequences down to species or strain. The total genera identified were
as follows: week 2, 301 experimental, 273 control; week 6, 183 experimental, 184
control; week 11, 292 experimental, 331 control; and week 23, 482 experimental, 483
control (Supplemental Material). Overall, 694 genera were identified across both groups
and all time points. The most prevalent genus in all groups and time points was
Prevotella. Other prominent genera included Bacteroides, Butyrivibrio, Catabacter,
Clostridium, Dialister, Lactobacillus, Olsenella, Oribacterium, Parvimonas, RC9,
Ruminococcus, Selemonas, and Streptococcus (Supplemental Material).
228
8.4.4 Real-time PCR
Protozoal density in both control and experimental groups increased over time until they
leveled off at approximately 2 x 103
(Figure 8). Control group had statistically higher
(p<0.05) densities at weeks 8 and 23. Methanogen densities increased for the first month,
then rapidly decreased at week 6 (Figure 8). Levels peaked at week 8, at which point
densities decreased to week 11, then peaked again at week 15. While average density
was higher in control lambs for most time points, due to the variability of densities within
groups this was not statistically significant. In lambs with elevated protozoal densities,
methanogen density was also elevated (Figure 9). When protozoal densities were low,
methanogen densities were also low. However, this trend was not statistically significant
(R2=0.376)
8.5 Discussion
Neither weight gain nor wool quality was improved in lambs given a probiotic, however,
dietary efficiency was increased as evidenced by the reduced feed intake (and rearing
costs) without a significant loss to weight gain. This reduction in rearing costs would be
further amplified using more traditional husbandry practices, such as rearing lambs
outside and giving them access to grass during weaning, thus precluding the need to
supplement with hay. Additionally, the probiotic lambs had a lower acetate to propionate
ratio than control lambs, which has previously been shown to indicate increased dietary
229
efficiency (Van Soest, 1982; Morgavi et al., 2012). An increased production of
propionate reduces free hydrogen in the rumen, making it less available to methanogens.
Sampling coverage was high in the first two time points, after which it decreased.
Conversely, Shannon, Inverse Simpson, CHAO, and ACE were low and increased over
time, all of which is a function of the increasing diversity of the rumen microbiota as the
rumen develops. While there were differences between groups in terms of statistical
diversity, there was no difference in OTUs/ sample between groups, and this is likely due
to evenly subsampling the data set. The experimental group had a higher diversity at the
beginning of the experiment, but this was not persistent.
Fibrolytic bacteria made up the majority of sequences identified in samples, and while
some fibrolytic genera were elevated in the experimental group, this was not consistent
across all time points. In all time points and both groups, Prevotella was the most
prevalent genus, while Butyrivibrio and Ruminococcus were also prevalent. All three
genera have previously been shown to be fibrolytic (Smith et al., 1973; Maglione et al.,
1992; Daniel et al., 1995; Cotta and Forster, 2006; Suen et al., 2011). However,
sequences from the probiotic strains could not be confidently reported in the sequenced
samples.
230
While protozoal densities increased over time and were stable, methanogen densities
varied greatly in the first six months of life for lambs. This is likely due to the changing
diet and bacterial populations in the rumen. For example, when methanogen density
decreased at week 6, the proportion of acetogenic bacteria increased (i.e. phylum
Actinobacteria, and species such as Acetivibrio and Acetitomaculum in the phylum
Firmicutes, class Clostridia), fostering competitive pathways to methanogenesis (Lopez
et al., 1999). Reducing methanogenesis would not only make for more eco-friendly
livestock, but would also reduce the amount of energy lost to the host which might have
otherwise been used for production.
Despite the small increase in dietary efficiency, a more dramatic increase in production
might result from altering the probiotic administered in the present study. Increasing the
dosage, using a different mix of fibrolytic bacteria, or using a probiotic with fibrolytic
and lactic-acid bacterial strains, are all potential methods of improving upon the results
presented here.
8.6 Acknowledgements
The authors would like to thank Matt Bodette, Laura Cersosimo, Sam Frawley, Emma
Hurley, Anjana Mangalat, Katy Nelligan, Scott Shumway, Sam Rosenbaum, Lee Warren,
and Sarah Zegler for their assistance with animal husbandry and sample collection,
Louise Calderwood for facilitating the transfer of lambs from UVM to Sterling College,
231
Mike Richards for care of sheep at Sterling College, and Dr. Sabrina Greenwood for
assistance with UVM Miller Farm facilities used for this project.
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8.8 Figures
Figure 8-1 Group weight (kg) means over time.
Significance is denoted with *, and error bars show standard error mean.
237
Figure 8-2 Group pH means over time.
Significance is denoted with *, and error bars show standard error mean.
238
Figure 8-3 Volatile fatty acid (VFA) and ethanol profile of groups (E=experimental, C=control) for
two time points on pasture.
0
50
100
150
200µ
Mol/
ml
(SE
M)
Ethanol
Valerate
Lactate
Isovalerate
Isobutyrate
Butyrate
Propionate
Acetate
*
*
*
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Figure 8-4 Acetate to propionate ratio, with SEM.
Figure 8-5 Principal component analysis of samples by sampling time: May=teal, June=green,
July=red, and October=dark blue.
0
2
4
6
8
10
wk5 wk6 wk7 wk8 wk9 wk11 wk15 wk23
Exp
Con
* * *
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Figure 8-6 Diversity at the phylum level for all sequencing time points.
Error bars show standard error mean.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
other
Synergistetes
Proteobacteria
Fibrobacteres
Actinobacteria
Firmicutes
Bacteroidetes
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Figure 8-7 Diversity at the family level for all sequencing time points. Error bars show standard error mean.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100% other
Succinivibrionaceae
Fibrobacteraceae
Coriobacteriaceae
Lactobacillaceae
Synergistaceae
Family_XI_Incertae_Se
dis
Streptococcaceae
Erysipelotrichaceae
Veillonellaceae
Ruminococcaceae
Lachnospiraceae
Bacteroidaceae
BS11
S24-7
p-2534-18B5
Rikenellaceae
Prevotellaceae
242
Figure 8-8 Real-time PCR data for methanogens and protozoa. Significance is denoted with *, and error bars show standard error mean.
243
Figure 8-9 Comparison of methanogen versus protozoal densities for all samples
.
244
8.9 Tables
Table 8-1 Diversity statistics per sample for each of the four sampling time points.
Results are listed by group, Experimental (n=10) and Control (n=10), or All (n=20).
Group 5-1-14 6-4-14 7-10-14 10-1-14
Total sequences
which passed QA
steps
All 953,581 1,002,520 501,909 1,007,093
Subsampled to 10,000/sample (200,000/time point)
Good’s Coverage
Exp 0.85 0.83 * 0.63 0.32 *
Con 0.87 0.87 0.62 0.28
Shannon-Weiner
Diversity
Exp 3.23 3.69 * 5.82 7.86 *
Con 3.25 3.09 5.72 8.10
Inverse Simpson
Exp 6.34 8.02 21 220 *
Con 6.35 6.15 19 447
CHAO Exp 10,907 11,489 * 50,674 95,992
Con 8,513 7,712 57,141 111,950
ACE Exp 31,864 31,738 * 149,728 278,155
Con 22,578 21,378 171,878 352,438
Total species-level
OTUs All 20,706 21,035 70,062 106,823
Mean species-level
OTUs/sample
Exp 1,271 1,425 3,918 5,700
Con 1,156 999 3,977 6,190
Shared OTUS
(sequences) All 9 (65,731) 7 (68,258) 20 (64,589) 19 (19,215)
Group shared OTUs
(sequences)
Exp 13
(72,661)
12
(65,582) 38 (96,060) 31 (78,967)
Con 12
(77,050)
12
(63,501) 37 (95,910) 33 (81,424)
AMOVA (p-value)* All 0.01* 0.73 0.30 0.14
Weighted Unifrac* All 0.80 * 0.47 0.44 0.57 *
Unweighted Unifrac* All 0.87 * 0.67 * 0.77 * 0.87 *
*Denotes statistically significant value (p<0.05) between groups at that time point.
245
8.10 Supplemental Material
This table has been modified from the original, which is too large to include here. It was
modified to include the top genera by abundance.
taxon
Exp
erim
enta
l w
eek
2 %
Con
trol
wee
k 2
%
Exp
erim
enta
l w
eek
6 %
Con
trol
wee
k 6
%
Exp
erim
enta
l w
eek
11 %
Con
trol
wee
k 1
1 %
Exp
erim
enta
l w
eek
23 %
Con
trol
wee
k 2
3 %
Acholeplasma 0.0 0.0 0.6 0.3 0.1 0.3 0.5 0.2
Acinetobacter 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Actinobacillus 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0
Aggregatibacter 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Alysiella 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Anaeroplasma 0.0 0.0 0.1 0.2 1.2 0.3 0.0 0.0
Anaerostipes 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.1
Anaerovorax 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0
Bacillus 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0
Bacteroides 3.7 13.6 0.1 0.1 1.2 1.0 1.3 1.6
Bergeriella 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Blautia 0.1 2.3 1.1 1.9 0.3 0.3 0.3 0.4
Butyrivibrio 0.2 0.1 3.1 0.5 2.8 1.5 1.2 2.6
Butyrivibrio-
Pseudobutyrivibrio 0.0 0.0 0.2 0.1 0.5 0.4 0.5 1.0
Catabacter 0.1 2.9 0.2 0.0 0.1 0.1 0.1 0.1
Clostridium 0.0 0.0 0.0 0.0 0.0 0.0 1.2 0.6
Coprococcus 0.1 0.0 0.1 0.1 0.3 0.3 0.6 1.0
Desulfovibrio 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2
Dialister 0.0 0.0 0.0 0.0 0.0 0.0 2.7 2.6
Dorea 0.1 0.2 0.0 0.0 0.0 0.0 0.0 0.0
Erysipelothrix 0.0 0.3 0.0 0.0 0.0 0.0 0.0 0.0
Eubacterium 0.5 0.2 0.0 0.0 0.1 0.1 0.1 0.1
Faecalibacterium 0.0 0.0 0.1 0.0 0.2 1.0 0.1 0.2
Fastidiosipila 0.2 0.3 0.3 0.0 0.1 0.2 0.2 0.2
246
Filifactor 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Fusobacterium 0.1 0.2 0.0 0.0 0.0 0.0 0.0 0.0
Geosporobacter 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Guggenheimella 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Helcococcus 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0
Hydrogenoanaerobacterium 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
Incertae_Sedis 2.2 4.3 6.4 3.6 1.6 1.7 3.2 4.1
Johnsonella 0.0 0.0 0.0 0.0 0.1 0.1 0.4 0.4
Lactobacillus 1.8 4.0 0.0 0.0 0.0 0.0 0.0 0.0
Mannheimia 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0
Megasphaera 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.1
Mogibacterium 0.1 0.4 0.1 0.0 0.1 0.1 0.0 0.0
Moraxella 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0
Moryella 0.0 0.0 0.2 0.2 0.2 0.2 0.2 0.3
Neisseria 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Olsenella 0.0 0.0 11.2 10.4 0.1 0.1 0.1 0.1
Oribacterium 0.0 0.0 9.7 10.5 0.2 0.4 0.1 0.1
Oscillibacter 0.1 0.0 0.0 0.0 0.1 0.1 0.0 0.1
Oscillospira 0.0 0.0 0.0 0.0 0.6 0.3 0.0 0.0
Parabacteroides 0.1 0.0 0.0 0.0 0.2 0.2 0.1 0.1
Parvimonas 0.0 0.0 0.0 0.0 0.0 0.0 6.4 2.4
Pedobacter 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1
Peptostreptococcus 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Porphyromonas 0.8 0.4 0.0 0.0 0.0 0.0 0.0 0.0
Prevotella 33.3 13.7 35.4 38.2 42.4 42.9 31.9 32.9
RC9 0.7 0.5 1.8 0.6 5.5 4.4 6.9 6.6
Roseburia 0.0 0.1 0.2 0.1 0.1 0.2 0.3 0.5
Ruminococcus 0.1 0.0 2.4 2.6 1.8 1.1 0.7 0.8
Selenomonas 0.0 0.0 0.2 0.0 0.6 0.4 8.8 5.7
Soehngenia 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Solobacterium 0.2 0.9 0.2 0.1 0.3 2.8 0.1 0.2
Spirochaeta 1.2 0.4 0.1 0.2 0.0 0.0 0.0 0.0
Streptococcus 0.2 9.9 0.0 0.0 0.0 0.0 0.0 0.0
Subdoligranulum 0.3 0.1 0.0 0.0 0.0 0.0 0.1 0.1
Succiniclasticum 0.0 0.0 0.1 0.2 0.0 0.0 0.4 0.3
Tannerella 0.1 0.1 0.0 0.0 0.1 0.1 0.1 0.1
Treponema 0.0 0.0 0.5 0.6 0.1 0.1 0.0 0.1
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vadinBC27 5.9 2.6 0.1 0.0 0.2 0.2 0.0 0.2
Victivallis 0.0 0.0 0.1 0.0 0.1 0.2 0.0 0.1
Xylanibacter 0.0 0.0 0.1 0.1 0.2 0.1 0.3 0.5
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CHAPTER 9 CONCLUSION
9.1 Summary
It was hypothesized that the moose would host novel microorganisms; that these
microorganisms would be capable of a wide variety of enzymatic functions; and that
these microorganisms could be used to improve other systems. The objectives of this
work were to identify the bacteria (CHAPTERS 2, 3), archaea (CHAPTER 5), and
protozoa (CHAPTERS 4, 5) present in the rumen of moose; to culture bacteria from the
rumen of the moose in order to study their biochemical capabilities (CHAPTERS 6, 7);
and to apply those cultured bacterial isolates to improve fiber digestion in neonate lambs
(CHAPTER 8).
9.2 The moose rumen: summarized findings and unanswered questions
Despite the extensive work presented here on the moose rumen microbiota, it cannot be
said that the moose rumen is yet fully understood. A large proportion of bacteria and
protozoa taxa studied here could not be identified, indicating that there are yet more
novel taxa which need to be isolated, cultured, classified, and deposited into reference
databases. This is particularly necessary for the protozoa, since relatively few species
have been cultured and identified. As much of that work was done prior to the
emergence of DNA sequencing technology, and given the difficulty in maintaining
protozoa in culture, even fewer of the known GIT species have 18S rRNA sequences
249
available in public databases (currently <250 sequences). In addition, fungi have barely
been investigated in the moose GIT [1], and the bacteriophages not at all.
Aside from the literature and work presented here on SSU rRNA, no work has been done
on the moose rumen microbiome: the enzymes at work, the myriad beneficial or toxic
products being produced, and the wealth of undocumented microbial genetic material
present. The bacteria in the rumen of the moose are predominantly fibrolytic, as they
should be given the diet of moose. However, is this fibrolytic dominance seasonally tied
to diet quality, forage content, and cellulose intake, as speculated and shown previously
[2–4], or is the fibrolysis in fact accomplished by different bacterial species in different
locations regardless of season. The genus Prevotella has been shown to be amylolytic
and fibrolytic, but without increased sensitivity of identification it remains to be seen
which species or subspecies is present, and which digestive function those found in the
Alaskan moose were performing. Targeted sequencing of known genes which code for
fibrolytic enzymes, or shotgun sequencing of the entire rumen contents to target full-
genomes, would reveal the enzymatic potential of the rumen as a whole. Known and
putative enzymes could be identified from DNA sequencing or microarrays, and the
functional microbiome can be studied using RNA sequencing or microarrays.
Previously, in vitro [5] or in vivo [6, 7] work was used to study digestibility of plant
matter by the moose rumen microorganisms.
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In the work presented here, methanogens in the moose rumen were identified for the first
time; although actual methane production in moose was not studied, either in vitro or in
vivo. It was speculated here that moose might have a lower production of methane than
other ruminants due to the high proportion of forage in their diet [8] and faster rate of
food passage through their GIT [9]. Previously, an in vitro study of biogas production
from GIT methanogens showed that moose rumen microorganisms produced less biogas
than those from beaver [10]. An ability to efficiently digest cellulose leads to a reduction
in methanogenesis [11]; however, the digestion of starch, also can reduce methanogenesis
via two means. Firstly, the production of propionate is increased which sequesters free H
and prevents its use in methanogenesis [12]. Second, the increase in amylolytic bacteria
reduces the pH, which in turn reduces the protozoal population, again providing less H
for methanogenesis [12]. Thus, it is likely that moose produce less methane than other
ruminants, although it is possible that this may be location/diet specific.
Methane production from moose can be most easily studied using anaerobic culturing,
either of pure methanogen cultures or whole rumen contents. One method would be to
use a tabletop methane digester, but any containment system which allowed for the
introduction of plant biomass and the collection of biogas could be used. An in vivo
study could be performed using methane collection systems such as a respiration
chamber, combined feeder/gas measurement systems, or by estimating methane output by
251
measuring the output of a tracer gas [13]. Given the size of moose and the relative few
numbers of captive moose available, this would seem impractical.
9.3 Fibrolytic probiotics in lambs: beneficial or bust?
The administered probiotic did not produce the expected results; however, it cannot be
considered a failed hypothesis. Weight gain was not improved in experimental lambs
over control lambs, with the exception of a period after starter grain was introduced in
which experimental lambs gained 30% body weight over the previous week, which was
the highest percent gain at any point in either group. This may be an indication that the
rumen and rumen microbiota of experimental lambs were more developed, and were able
to take advantage of a solid food diet more quickly than those of control lambs. Rumen
papillae and intestinal villi length measurements were not able to taken; however, they
would have provided insight into whether the GIT of probiotics lambs were, in fact, more
developed. This might have been performed using GIT epithelial samples for traditional
histological slides or scanning with micro-computed tomography (micro-CT) [14] to
measure length and differentiation. When put in the context of feeding costs per kg of
body weight; however, the lower cost of raising the probiotic lambs without sacrificing
weight gain is indicative of an increased dietary efficiency.
Although total wool growth was significantly higher in experimental lambs, wool quality
was not improved over that of control lambs. Wool quality is determined by staple
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(fiber) length, strength, diameter, and diameter uniformity. Thinner diameter wool (<22
microns) can be woven into a thinner, finer yarn, and thus is more valuable. The sheep
used in this study were varieties of Dorset-crosses. Dorset is a dual-purpose breed,
producing good quality meat and medium quality (avg. 27-33 microns) white wool. On
the farm from which the lambs were obtained, sheep were mainly bred for meat and dairy
(cheese) production, although wool was also collected and sold. It may be that any
positive effects of the probiotic were not enough to overcome the genotypic
determination of wool quality.
The probiotic lambs had a higher and more stable pH than control lambs through weaning
(Figure 1). A stable pH is important when transitioning between diets, especially when
transitioning to a highly digestible starch, such as grain, to prevent a low rumen pH
which can kill rumen microorganisms and disrupt digestive function. Sheep are not
prone to rumen acidosis, unless they gain access to a high-starch feedstuff and gorge
themselves. However, dairy cattle are more sensitive to rumen acidosis, which can
decrease production and may require medical intervention (SECTION 1.3.5). As the
lambs in the probiotic study were acting as a model for cattle, a stable rumen pH would
be an important benefit of the probiotic.
It is difficult to determine whether the probiotic strains properly colonized the rumen or
not, as the amplicons used for analysis did not have the resolution to be identified past
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genus or, in some cases, family. Difficulty identifying Illumina sequences down to genus
level has previously been seen [15]. In the present work, a variety of reference databases
(i.e. GenBank, RDP, Silva) were used, as well as multiple classification methods (i.e. k
nearest neighbor, wang [16]) and confidence cutoff levels, in an effort to classify down to
species and subspecies, but to no avail. The genera Bacillus and Staphylococcus were
identified, but in low numbers in both groups. The probiotic strains may have colonized
the rumen of experimental lambs, validating the hypothesis that the lamb rumen diversity
could be altered long-term, but without providing the anticipated beneficial effects.
It is possible that the dosage of bacteria was not high enough to allow for larger-scale
colonization of the rumen. It may also be the case that the isolates tested were not ideal
for colonization in some way which was not investigated beforehand (0). For example,
isolates may be sensitive to antimicrobial products released by other rumen
microorganisms, or may have been subject to predation by protozoa. To improve the
identification of probiotic strains, sequencing using longer amplicons or with another
platform could be attempted to improve the resolution. Another method would be to
create strain-specific real-time PCR primers and look at 16S copy number in whole
samples. PCR product would have to be amplified using additional cycles in order to
generate a detectable signal if there are very low copy numbers. Potentially, whole
rumen samples could be used to reisolate the probiotic strains in culture; however, this
method would be the least efficient.
254
Probiotic strains were shown to survive in milk replacer for a period of time, which
allows for the potential of administering during bulk-feeding. The probiotic was not
tested as a top-dressing; either as a live culture or dried cells, but this represents another
possible means of administering the probiotic to many animals simultaneously.
However, despite the benefits provided by the probiotic as outlined previously, the
probiotic is not a viable product in its current form. To be useful to producers, a
significant economic difference in animal product quality or production cost must be
shown. Though a reduction in production (rearing) cost was shown, it is not enough to
compensate for the estimated cost of adding a probiotic product. A more dramatic
increase in production might result from altering the probiotic administered in the present
study. Increasing the dosage, using a different mix of fibrolytic bacteria, or using a
probiotic with fibrolytic and lactic-acid bacterial strains are all potential methods of
improving upon the results presented in CHAPTER 8. Additionally, probiotic benefits
may be more pronounced when administered to dairy cattle, or when also measuring milk
production. Immunological measurements, such as inflammation in the gut, GIT
cytokines, blood cortisol, blood cholesterol, or meat quality measurements, such as
concentrations of fatty acids, could also be used to detect beneficial changes caused by
the probiotic other than a direct increase in production.
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9.4 Molecular methodology
9.4.1 Sequencing Platform
High-throughput sequencing was chosen as the platform for the main work presented in
this dissertation, as the previous investigations into the moose rumen had been using
anaerobic culturing or light microscopy [17–21]. Initially, preliminary investigations into
the rumen and colon bacteria of the moose were made using DNA microarray chips [22].
It quickly became clear that this did not provide the sensitivity to detect specific genera
of interest, nor was it capable of identifying unknown taxa. The DNA chip was able to
quickly determine broad differences in diversity between samples, and in the years since
the DNA microarray experiment was performed in 2011 [22], the chip has been
redesigned to detect 50,000 bacterial taxa using over a million different probes.
Multiplexed sequencing-by-synthesis was the next obvious choice, using barcoded
primers to sequence multiple samples simultaneously; however, there were multiple
platforms to choose from. In 2011, when the first data sets were being considered for
sequencing, Roche 454 was the more appropriate platform. It was capable of producing
de novo sequences up to 400-500 bases in length, with tens of thousands of sequences
generated per sample. To perform pyrosequencing, the Roche platform uses a cyclic
flow of nucleotides over a plate containing wells, with one strand of ssDNA per well.
When a nucleotide triphosphate matched the candidate sequence it would hybridize via
256
DNA polymerase. This would release pyrophosphate, which is converted by ATP
sulfurylase to ATP and used by luciferase to convert luciferin to oxyluciferin.
This reaction produces a measurable amount of light, which is measured by a camera and
converted to a “flow value”, and is outputted as a flowgram. Flow values do not directly
translate to a specific number of nucleotides, thus is was necessary to use bioinformatics
algorithms such as PyroNoise [23] to determine the number of bases in the flow using
maximum likelihood. This provided an extra step of quality assurance, as candidate
flowgrams can be compared to reference flowgrams generated from mock data sets and
adjusted to remove noise [23, 24].
Aside from Roche, the most promising platform being developed was Illumina, which at
the time boasted 25-100 bases, with millions of sequences generated. The Illumina
platforms were faster, as four different fluorescent dyes were used to tag nucleotide
bases, thus negating the need to pause between read steps. Once the nucleotide base was
incorporated, the dye was cleaved and diffused out of the read zone. However, the
sequence length being generated was simply not long enough for taxonomic resolution.
For large contig-assembly and full-genome sequencing, the shotgun sequencing approach
of Illumina works well and continues to expand its potential [25].
257
The Illumina platforms rapidly evolved, and just a few short years later were able to
produce amplicons of 400-500 bases using paired-end reads, although by this time Roche
was still outpacing them at 800-1,000 base non-paired reads [26]. It also became more
economical than Roche sequencing, as fewer reagents were required and sequencing
preparation time was greatly reduced [27]. In late 2013, Roche announced that it was
closing the 454 Life Sciences subsidiary and discontinuing the 454 reagents by 2016,
further driving an industry-wide switch from Roche 454 to Illumina platforms.
The Illumina platforms came with their own drawbacks. Raw error rates were higher [27,
28], especially after the first 60 nucleotide bases [15], although consensus finished-read
accuracy was 99% [29]. Data output came in the form of fasta files, as opposed to Roche
which provided flowgrams that could undergo noise reduction. Additionally, Illumina
sequencers showed lower coverage in high GC regions [30]. The sheer number of
sequence reads produced created problems during analysis as random access memory
(RAM) and hard drive space became limiting.
With respect to the data generated in this project, Roche 454 was the optimal platform for
investigating bacterial 16S rRNA sequences and protozoal 18S rRNA sequences, and
Illumina’s MiSeq platform was optimal for investigating archaeal 16S rRNA sequences.
For example, when sequencing protozoa from three pooled Alaskan moose rumen
samples using Roche 454, a total of 12,326 sequences passed QA steps, which were
258
represented by 769 unique (non-redundant) sequences [31]. When sequencing protozoa
from these same three samples individually using MiSeq ver. 3, a total of 200,513
sequences passed the same QA steps, represented by 99,895 unique sequences [32]. This
was a gross overestimation of protozoan diversity, and required more stringent analysis
parameters to correct the data, such as using a higher quality score cutoff, or condensing
sequences which had one or two polymorphic differences between them.
Likewise, when analyzing bacterial sequences generated from the lamb probiotic study,
MiSeq ver. 3 generated over 1 million raw sequences per data set of 20 samples
CHAPTER 8). After stringent QA steps, between 500,000 and just over 1,000,000 total
sequences were retained per data set, over 75% of which were considered unique. Again,
this was an overestimation of diversity, but without the ability to reduce sequencing noise
in the original sequences there was no way to detect raw sequencing errors. Additionally,
computer RAM became limiting, and to accommodate such a massive amount of data
needed to calculate genetic distance and cluster sequences into OTUs, it was necessary to
subsample the data sets.
9.4.2 Sequencing Target
Properly selecting a sequencing target is extremely important as it impacts all aspects of
the project: from PCR amplification, to sequencing reactions, to DNA sequence analysis.
As previously mentioned (SECTION 1.2), the SSU rRNA gene was chosen as the target
259
for phylogenetic studies. As current high-throughput sequencing techniques were limited
in the length of high-quality, low-error sequences which could be generated, a section of
the rRNA gene was needed as a proxy for the full-length sequence. In addition to being
the optimal size for high-throughput sequencing (~500 b), the amplicon needed to be easy
to generate in the lab, have a trustworthy and expansive (when possible) reference
database of sequences available for comparison [33–35], and not be liable to
amplification bias by primers [15, 36, 37]. Most importantly, the amplicon needed to
provide a similar statistical estimate of diversity and resolution for identification as when
using the full-length gene [15, 38–40]. Thus, it was determined that for the presented
work, the V1-V3 region of the 16S for bacteria and archaea, and the V3-V4 region of the
18S for protozoa, provided the overall best solution to the current constraints and the
selected sequencing platform.
Most studies which investigate the microbiota of a certain environment tend to focus on
one domain at a time, or employ different methods to investigate different taxa (i.e.
bacteria, archaea, protozoa, and fungi). However, some phylogenetic studies attempt to
use the same primers and amplification parameters across multiple kingdoms. While this
may be a more efficient approach in terms of time, money, and effort in the laboratory, it
is not an adequate means of investigation. For example, studies which use “universal
prokaryotic primers” to co-amplify bacteria and archaea result in very few archaeal
sequences as compared to the number of bacterial sequences generated [41–43]. In the
260
GI tract, archaeal density is only 1-2 logs lower than bacterial density, thus “universal”
PCR parameters for the 16S gene overwhelmingly underrepresents archaea. Likewise,
“universal eukaryotic primers” often marginalize protozoal sequences [42, 44]. In some
instances, primers which were prokaryote-specific have been used to amplify eukaryotic
18S sequences [45, 46].
9.4.3 Bioinformatics Programs and Analysis
MOTHUR [24] was selected as the bioinformatics platform of choice as it integrated a
comprehensive list of analytical functions within the same platform, was more user-
friendly than other programs, and was compatible with Windows, Mac, and Linux
operating systems. Notably, it integrated a version of PyroNoise [23] which reduced
noise in pyrosequencing flowgrams generated from Roche 454 platforms, as well as a
wide variety of chimera checking algorithms.
Two of the more popular chimera checking programs, UCHIME [47] and ChimeraSlayer
[48], were compared using bacterial 16S rRNA sequences from the moose rumen
generated using the Roche 454 platform (CHAPTER 3). UCHIME identified 18,146
chimeras out of a total 40,514 sequences, or 45% of sequences as chimeric, when using
abundance to estimate chimeras. Using the same data set, again using abundance to
estimate chimeras, ChimeraSlayer identified 17,225 chimeric sequences, or 43%.
However, 14,933 out of the 18,146 UCHIME putative chimeric sequences (82%) were
261
able to classify with >80% confidence. For ChimeraSlayer, 14,268 out of the 17,225
putative chimeric sequences (83%) could be classified with >80% confidence. Using the
Silva bacterial 16S reference file to estimate chimeric sequences reduced the percentage
of sequences being identified as chimeric, as well as reduced the percentage of those
which could actually be classified with a reasonable amount of confidence. Thus,
UCHIME with a reference database was used for all further analyses.
Reference alignments for bacteria, archaea, and eukaryota from the Silva [49],
Greengenes [50], and RDP [34] databases were provided for use with MOTHUR. The
Silva database for bacteria was found to generate better alignments and classification than
the RDP reference database (Table 1). Owing to the unique nature of the archaeal and
protozoan sequences being investigated, and the low number of available rumen ciliate
protozoan sequences in any database, it was necessary to generate in-house reference
alignments for both using publically available sequences [31, 32].
9.5 References
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9.6 Figures
Figure 9-1 Mean rumen pH over time, with standard deviation bars.
268
9.7 Tables
Table 9-1 A comparison of the Silva bacterial database vs the Ribosomal Database Project (RDP)
bacterial reference files in ability to classify 16S rRNA gene bacterial sequences.
Silva Silva % RDP RDP %
Total Unique sequences 33,622 33,622
Total classified as Bacteria 33,622 100% 33,610 99.96%
Total classified as Archaea 0 0% 1 ~0%
Unclassified at the Domain level 0 0% 11 0.03%
Total classified at the Phylum level
(excl. Unclassified) 28,111 83.61% 26,769 79.6%
Total classified at the Family level
(excl. Unclassified) 21,122 62.82% 16,277 48.41%
Total classified at the Genus level
(excl. Unclassified) 10,642 31.66% 3,700 11.00%
Total classified at the Species level 0 0% N/A
Total Unclassified bacteria 5,511 16.39% 6,841 20.34%
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