MMI 301 Quorum Sensing
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What is quorum sensing
Cell-cell signaling used to control specific genes, allows coordination of group activities
Best studied system for QS?
- acyl-homoserine lactone (AHL) QS in proteobacteria
- -Many species
- -Signals are dedicated
- -Made by AHL synthases, bind to protein receptors
- -Regulate different things in different species
How does it work (basic)
All cells send out signals, only when signal concentration is high enough (enough nearby cells) does the gene get transcribed.
How does Pseudomonas aeruginosa us QS?
When high density, activate genes for virulence and biofilm formation
- Produced in response to high QS, made of extracellular polysaccharide matrix
- Large '3D' structures
What kind of QS do Gram +/- use
- AHL-type=Gram -
- Peptide-type= Gram +
What synthesizes AHL QS molecules?
LuxI protein homologs
QS systems in Vibrio fischeri
- Synthase-->Signal-->Regulatory protein
C8 signal pathway
- C8 INHIBITS luxO
- luxO INHIBITS litR
- litR STIMULATES luxR
- luxR and C6 STIMULATE luxlCDABEG
Purposes of bioluminescence
Avoid predators, Attract prey, Interspecies communication
Bobtail squid use what bacteria for light
What fischeri strains will survive in bobtail organ
Ones that produce light (despite being less fit in a 'vacuum')
What are the strains of Fischeri
GFP and RFP, green and red fluorescent proteins
How to assay for bacterial colonization of bobtail
either plate/count light organ homogenate or measure light given off by squid.
How is luminescence produced
- reduced flavin to oxidized flavin and aldehyde to acid
In general you have a luciferin turning into an oxy luciferin
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