Molecule quorum sensing

If we think about it for a bit, quorum sensing as a mechanism regulating the production of virulence factors makes good sense for the bacterial population. If the bacterial population is too low, secretion of virulence factors would seem to be of little use too few bacteria secreting too few virulence factor molecules to serve whatever purpose these serve for the bacteria. It would seem better to wait until the bacterial forces have massed, then release the virulence factors and have some real impact. 

Quorum sensing the ability of bacteria to coordinate their behavior through response to signaling molecules. 

Antibiotic production and morphological differentiation (formation of aerial mycelium and sporulation) in Streptomyces species and in some other actinomycetes is regulated by small signaling molecules called y-butyrolactones or butanolids. These quorum-sensing signals bind to... 

Fig. 6. Quorum sensing molecules in yeast farnesol, tryptophol and tyrosol.

Chen H, Fujita M, Feng Q, Clardy J, Fink GR, Tyrosol is a quorum-sensing molecule in Candida albicans, Proc Natl Acad Sci USA 101 5048—5052, 2004. 

Ritchie AJ, Jansson A, Stallberg J, Nilsson P, Lysaght P, Cooley MA (2005) The Pseudomonas aeruginosa quorum-sensing molecule N-3-(oxododecanoyl)-L-homoserine lactone inhibits T-cell differentiation and cytokine production by a mechanism involving an early step in T-cell activation. Infect Immun 73 1648... 

Further, compartmentalization allows cells to control the import of nutrients and the export of products that manipulate the environment, or excrete waste. These include siderophores that enhance uptake of metal ions, quorum-sensing molecules that inform cells of the presence of others of their kind, molecules that form biofilms that allow attachment to surfaces and protection from mechanical and chemical stress, and toxins that inhibit the growth of competitors. 

The third system is also related to both Las and Rhl systems, but not to the AHL-mediated one. The signal molecule is 2-heptyl-3-hydroxy-4-quinolone (PQS). PQS quorum sensing system is described in Section 4.07.5.3.2. 

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