growth b
TRANSCRIPT
Microbial Growth
“Because individual cells grow larger only to divide into new individuals, microbial growth is defined not in terms of cell size but as the increase in the number of cells, which occurs by cell division."
Bin
ary
Fis
sion Note nascent septum forming
Pla
nes
of D
ivis
ion
(1/3
)
Diplococcus
Streptococcus
Pla
nes
of D
ivis
ion
(2/3
)
Tetrad
Sarcinae
Pla
nes
of D
ivis
ion
(3/3
)
Staphylococcus
Exp
onen
tial G
row
thNote Logarithmic Scale
Exp
onen
tial G
row
th
Decline (Death) Phase
Solid Medium
Bacterial Colonies
• Standard Bacterial Count
• Colony-Forming Units
• Plaque-Forming Units
•Spread Plate
• Pour Plate
• Soft-Agar Overlay
Soft Agar Overlay
Spr
ead
& P
our
Pla
tes
Dilutions and Limitations
Serial Dilution
Direct Microscopic Count
Mos
t Pro
babl
e N
umbe
r M
etho
d
Mos
t Pro
babl
e N
umbe
r M
etho
dMost Probable Number Calculations
(based on 5 tubes/dilution)
dilutions (100 = 1 ml culure)
100 10-1 10-2 10-3 10-4 MPN/ml
5 5 1 0 0 33
4 5 1 0 0 33
5 4 4 1 0 40
5 4 4 0 1 40
5 5 5 5 2 5400
0 0 1 0 0 0.20
4 4 1 1 0 4.7
Det
erm
inat
ion
of T
urbi
dity
pH O
ptim
a
Neutrophiles
Aci
d-B
ased
Mic
robi
al S
ucce
ssio
n
Temperature Optima
Also Psychrotrophs & Thermodurics
Thermophiles
A large channel draining from a hot pool, containing carotenoid-rich microorganisms. The temperature of this channel in the foreground is about 60 oC. Layers of white-coloured limestone (forming a rock deposit known as travertine) can also be seen. Note the footprints of buffalo in the foreground. These animals often seek the warmth of thermal areas in the winter months.
limestone terraces formed by precipitation from calcium-rich water flowing from a raised hot pool. Pink, green and brown-coloured microorganisms occupy the thermal gradients in the flowing water (60-100oC)
Thermophiles
Deep-Sea Vents
Oxygen Requirements
Mic
roae
roph
iles
Cap
noph
iles
Gro
win
g O
blig
ate
Ana
erob
es
• Fluid Thioglycolate Medium
• Peptones, Yeast Extracts, Glucose
• Thioglycolate binds O2
• Agar slows diffusion of O2
• Resazurin is O2 indicator (red)
Salt Tolerance
Nutrient Acquisition—Exoenzymes
• Secreted into environment
• Catabolize food products
• Protease, DNAase, Amylase, Lipase
• Used in bacterial identification
Gro
win
g F
astid
ious
Mic
robe
s
Selective Media
Differential Media
Dia
gnos
tic M
edia
The concepts of Selective and Differential media can be confusing, particularly because very often media
are both Selective and Differential
Microbial Growth!
Win
ogra
dsky
Col
umn
AIRAIR
SANDSAND
SedimentSedimentCelluloseCellulose
CaSOCaSO44 + CaCO + CaCO33
WaterWater
Allows for the development Allows for the development of a redox gradient in a of a redox gradient in a sample, from anaerobic sample, from anaerobic through to Hthrough to H22S-richS-rich
Consists of water over Consists of water over sediment and substrate sediment and substrate (sometimes with sand)(sometimes with sand)
Other components (e.g.., Other components (e.g.., carbon sources, inorganic carbon sources, inorganic elements) often added.elements) often added.(these can be manipulated (these can be manipulated to select for different to select for different populations)populations)
Winogradsky Column
Example Winogradsky column Example Winogradsky column (from Atlas and Bartha 1999)(from Atlas and Bartha 1999)
Microbial ZonesMicrobial Zones reactionsreactions
Algae, cyanobacteriaAlgae, cyanobacteria COCO22 > CH > CH22O, HO, H22O > OO > O22
HH22S - oxidizersS - oxidizers HH22S > SS > S00, CO, CO22 > CH > CH22OO
Facultative anaerobesFacultative anaerobes CHCH22O > C0O > C02 2 + H+ H22
Purple non-sulfurPurple non-sulfur CHCH22O > HO > H22, CO, CO22 > CH > CH2200
photoheterotrophsphotoheterotrophs
Purple Sulfur BacteriaPurple Sulfur Bacteria HH22S > SS > S00, CO, CO22 > CH > CH22OO
Green Sulfur bacteriaGreen Sulfur bacteria H H22S > SS > S00, CO, CO22 > CH > CH22OO
Sulfate reducersSulfate reducers SOSO442-2- > H > H22S, CHS, CH22O > COO > CO22
Fermentative heterotrophs Fermentative heterotrophs CHCH22O > COO > CO22 + H + H22
HH22OO
AIRAIR
SANDSAND
SedimentSedimentCelluloseCellulose
CaSOCaSO44 + CaCO + CaCO33
Aerobic
Microaerophilic
Anaerobic
H2S
RedoxRedoxGradientGradient