Quorum sensing Flashcards
Quorum sensing
The regulation of gene expression in response to fluctuations in cell-population density
Bacteria response to presence of each other + chemicals produced by them
Autoinducer
Signaling molecules that are produced in response to changes in cell-population density
Varies depending on bacterial species
Structure for gram negative bacteria: acyl side chain (variable) + homoserine lactone ring (constant)
Concentration of autoinducer goes up in constrained space when population density is high
Peptide signalling
Signal system in gram positive bacteria e.g. S.aureus
Autoinducers in gram negative bacteria
Structure for gram negative bacteria: acyl side chain (variable) + homoserine lactone ring (constant) - AHL molecule
Conjugation + virulence signals
Involved in bioluminescence
Quorum
Specific cell density where concentration of signal molecule has reached its threshold to induce a change
Bioluminescence signalling system
LuX genes
R genes
Transcriptional regulator genes
I genes
homoserine lactone genes
What does is the las system involved in making
virulence factors such as elastase involved in extensive tissue damage in P.aerugenosa
also lipase and exotoxin A
Operons invovled in las system
lasR, rsaL, lasI
RsaL
Negative regulator of LasI
LasI
AHL synthase
Rhl system
AHL based sytem
Produces rhamnolipids
what gene encodes elastase
lasB
Rhamnolipids
Bacterial surfactant
glycosyl head group, Acting as wetting agents, RLs are essential for bacterial surface dissemination called swarming motility and for normal biofilm development
