Download - Quorum Sensing Regulation and Its Role In
![Page 1: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/1.jpg)
Abraham Mikru PhD seminar AAU 2010
1
Quorum Sensing Regulation And Its Role In The Legume-
Rhizobia Symbiosis
PhD Seminar By Abraham Mikru Teklemichael
Instructor: Fasil Assefa (PhD) Dpt. Biology, AAU 2010
![Page 2: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/2.jpg)
Abraham Mikru PhD seminar AAU 2010
2
Contents
• Introduction• General principles of quorum sensing• The Lux paradigm• QS in some rhizobia• Response of host plant • Concluding remarks
![Page 3: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/3.jpg)
Abraham Mikru PhD seminar AAU 2010
3
Introduction
• Microbes are not solitary
• Microbes interact with each other and their environment
• Microbial interaction is widespread & vast
• The focus here is on quorum sensing (QS) via acylhomoserine lactones (AHLs)
![Page 4: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/4.jpg)
Abraham Mikru PhD seminar AAU 2010
4
What is QS?• Cell Density-dependent regulation of gene
expression mediated by diffusible signal molecules
• “Molecular dialogue”• Bacterial ‘talk’ to each other & ‘ccrosstalk’• Bacterial chemical communication or
signaling
![Page 5: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/5.jpg)
Abraham Mikru PhD seminar AAU 2010
5
Why do bacteria communicate?
• Regulate gene expression concertedly• Orchestrate activities not achievable by a
single cell
• Coordinate population-wide behavioral response
• Behave as a multicellular organism• Rapid adaptation and survival
![Page 6: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/6.jpg)
Abraham Mikru PhD seminar AAU 2010
6
Behaviors controlled by QS
Among others:• Bioluminescence• Virulence• Symbiosis• Biofilm • Horizontal gene transfer
![Page 7: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/7.jpg)
Abraham Mikru PhD seminar AAU 2010
7
QS molecules (autoinducer)
• N-Acyl homoserine lactones (AHLs) or AI-1• In Gram negatives as well as rhizobia• Exclusively intraspecies communication
Hydrophilic head
Homoserine lactonering
Hydrophobic tailAcyl side chain
Variability•n= C4 -C18•R= H, O, OH•Unsaturation
![Page 8: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/8.jpg)
Abraham Mikru PhD seminar AAU 2010
8
Synthesis and accumulation
SAM= S-adenosyl methionineACP= acyl-carrier protein
3. Accumulation depends on:
•Cell density•Biofilm•Microcolony•Microenvironment •Degraders
2. Movement across membrane
•Diffusion•Active/carrier mediated
1
![Page 9: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/9.jpg)
Abraham Mikru PhD seminar AAU 2010
9
QS regulator (LuxR and homologues)
• AHL receptor and transcriptional regulator• Two regions of sequence conservation
Amino terminus binds to cognate AHLCarboxy terminus binds to target DNA
(Lux box)
![Page 10: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/10.jpg)
Abraham Mikru PhD seminar AAU 2010
10
AHL degraders
• Unstable under alkaline pH• AHL degrading enzymes • Produced by several rhizobacteria• Potentially interfere with QS
Lactonase (1) and Acylase (3)
![Page 11: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/11.jpg)
Abraham Mikru PhD seminar AAU 2010
11
When does QS occur?
At threshold [AHL] or when population is quorate
time
growth
Quorum sensing-regulated gene expression
Quorumsize
![Page 12: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/12.jpg)
Abraham Mikru PhD seminar AAU 2010
12
How many cells in a Quorate population? Depends…
Increasing Cell Density
[AHLs]
Critical [AHL]Specific Genes ON
Low cell density High cell density
![Page 13: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/13.jpg)
Abraham Mikru PhD seminar AAU 2010
13
General principle of QS and the Lux paradigm
• Cells make a signalling molecule (AHL) constitutively• The AHL diffuses freely out of the cell into the
surrounding medium• As the population of the cells grow, so does the
concentration of AHL in the growth medium• When the population (and hence AHL) concentration
reaches a threshold, the AHL moves back down its concentration gradient into the cell.
![Page 14: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/14.jpg)
Abraham Mikru PhD seminar AAU 2010
14
Cont.
• The concentration of AHL inside the cell now increases and AHL can bind to luxR – the transcriptional activator protein
• The luxR-AHL conjugate activates gene expression
• This system is often referred to as “autoinduction” or
• Positive feedback loop control
![Page 15: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/15.jpg)
Abraham Mikru PhD seminar AAU 2010
15
luxI codes for AHLSynthase
luxR codes forTranscriptional regulator
QS in Photobacterium fischeri (V.fischeri)
![Page 16: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/16.jpg)
Abraham Mikru PhD seminar AAU 2010
16
Bioluminescence at high cell density in culture and light organ
![Page 17: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/17.jpg)
Abraham Mikru PhD seminar AAU 2010
17
QS in Rhizobiacae
• QS now considered one of the requisite symbiotic signals
• Reported for many rhizobia
• In all cases AHLs are the signaling molecules
• The genI/genR (luxI/luxR homologues) system still remains
![Page 18: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/18.jpg)
Abraham Mikru PhD seminar AAU 2010
18
QS in R. leguminosarum
Four QS systems known
• cinI/cinR• raiI/raiR• rhiI/rhiR• traI/traR
![Page 19: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/19.jpg)
Abraham Mikru PhD seminar AAU 2010
19
cinI/cinR
• Located on chromosome
QS molecule is: • 3-OH-C14:1-HSL
Functions• Overall control of other QS systems• Stationary phase adaptation and survival• Growth inhibition (bacteriocin–like action)
![Page 20: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/20.jpg)
Abraham Mikru PhD seminar AAU 2010
20
raiI/raiR
• Located on non-symbiotic plasmid
QS molecules:• C8-HSL, 3-OH-C8-HSL• Function: unknown
![Page 21: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/21.jpg)
Abraham Mikru PhD seminar AAU 2010
21
rhiI/rhiR
• Located on symbiotic plasmid• Close to nod box
QS molecules• C6-HSL, C7-HSL and C8-HSL
Target genes• rhiI, rhiABC
Function• Influence nodulation
![Page 22: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/22.jpg)
Abraham Mikru PhD seminar AAU 2010
22
traI/traR
• Located on symbiotic plasmidQS molecules• 3-oxo-C8-HSL• 3-OH-C14:1-HSL from recipient
Other regulatory genes• bisR, traM
Target genes and functions• Induce plasmid transfer operon
![Page 23: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/23.jpg)
Abraham Mikru PhD seminar AAU 2010
23
QS network in R. leguminosarum
![Page 24: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/24.jpg)
Abraham Mikru PhD seminar AAU 2010
24
traI/traR
![Page 25: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/25.jpg)
Abraham Mikru PhD seminar AAU 2010
25
The R. etli Qs systems
• Possess orthologues of the cinI/cinR, raiI/raiR and traI/traR genes
• Target genes and functions are different• cinI/cinR: growth inhibition, symbiosome
development, nitrogen fixation and swarming motility
• raiI/raiR : Mutants show higher nodulation• traI/traR: conjugal plasmid (p42a)transfer
![Page 26: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/26.jpg)
Abraham Mikru PhD seminar AAU 2010
26
Interaction of two QS in R. etli CNPAF 512
![Page 27: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/27.jpg)
Abraham Mikru PhD seminar AAU 2010
27
S. meliloti QS systems
• sinI/sinR: EPS production, swarming motility and nodulation efficiency
• Involves several C12 to C18 AHLs • Some symbiotic genes dependent on sinR
but not on sinI. • What could be the signal molecules other
than SinI- made AHLS controls these genes?
• expR: role in EPSII synthesis
![Page 28: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/28.jpg)
Abraham Mikru PhD seminar AAU 2010
28
S. meliloti (Rm1021 and Rm41)
![Page 29: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/29.jpg)
Abraham Mikru PhD seminar AAU 2010
29
Mesorhizobium spp
Reported for several species
• M. huakuii: QS involved in biofilm formation• M. loti: three luxI-like genes influence
nodulation • M. tianshanense: QS involved in nodulation
![Page 30: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/30.jpg)
Abraham Mikru PhD seminar AAU 2010
30
Rhizobium sp.NGR234
• traI/traR genes on symbiotic plasmid pNGR234a
• QS molecule is 3-oxo-C8-HSL
Functions• Conjugal plasmid transfer• Growth inhibition
![Page 31: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/31.jpg)
Abraham Mikru PhD seminar AAU 2010
31
Bradyrhizobium japonicum
• QS inhibit nod gene expression• QS molecule is bradyoxetin not an AHL• Exhibit siderophor-like property• Maximal in iron depleted condition• AHLs detected in B. japonicum and B. elkani
but the target genes not known
![Page 32: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/32.jpg)
Abraham Mikru PhD seminar AAU 2010
32
Bradyrhizobium japonicum
![Page 33: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/33.jpg)
Abraham Mikru PhD seminar AAU 2010
33
Responses of host plants to QS
Plants ‘listen’ & respond to bacterial AHL QS• Medicago truncatula root respond to two
different AHLs by up regulating 154 proteins• The proteins function in defense,
transcriptional regulation, stress and plant hormone response
• Host plants also produce AHL-mimics potentially interfering with bacterial QS
![Page 34: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/34.jpg)
Abraham Mikru PhD seminar AAU 2010
34
Concluding remarks
AHL QS plays several role in rhizobia-legume symbiosis
• EPS production,symbiosome development, Nodulation efficiency,Nitrogen fixation
• Plasmid transfer • Stationary phase adaptation and Growth
inhibition Host plants also “listen” and respond to
bacterial AHL-QS
![Page 35: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/35.jpg)
Abraham Mikru PhD seminar AAU 2010
35
Thank You!
![Page 36: Quorum Sensing Regulation and Its Role In](https://reader033.vdocuments.us/reader033/viewer/2022061119/546a8335b4af9f8c7d8b4c4d/html5/thumbnails/36.jpg)
Abraham Mikru PhD seminar AAU 2010
36
Variations in structure of AHLs
A. tumefaciens, Rhizobium sp. NGR234, R. leguminosarum, B. S. meliloti, R. etli CFN42
R. leguminosarum, S. meliloti, R. etli CFN42
R. leguminosarum, S. meliloti
R. leguminosarum
S. meliloti