Quorum Sensing
http://www.ted.com/talks/bonnie_b
assler_on_how_bacteria_communica
te
Model Organism
• Lux operon
The basic mechanics
• autoinducers
• enable populations of bacteria to coordinate
regulation of gene expression and behavior,
on a community-wide scale
Autoinducers
• synthesized intracellularly.
• either passively released or actively secreted
outside of the cells.
• number of cells increases = extracellular
concentration of autoinducer increases.
• minimal threshold level required for detection
• Once threshold is hit, receptors bind the
autoinducers and trigger signal transduction
cascades that result in population-wide changes
in gene expression.
gene regulation
• Low level, kinase model of cell communication
• LuxO = regulator protein
• Product degrades mRNA that stimulates group
behavior
• High level – switch to phosphatases, LuxO
activity shuts down, mRNA that stimulates
group behavior is left intact  bioluminesce
End Product
• enables population of cells to function in
unison = collective behavior
• Achieve multicellularity – acting as one unit
Example:
• Virulence factor expression
– molecules produced by pathogens and contribute
to the pathogenicity of the organism
– Help to colonize niche in host, evade or inhibit
immune system of host, get energy from host, and
get into/out of host cells
Example:
• Formation of biofilms
– group of microorganisms in which cells stick to
each other on a surface
– Have different phenotypic properties than “freedwellers” of same species
– Embedded within self-produced matrix – slime
– Increased resistance to detergents and antibiotics
– Dental plaque is a perfect example
• http://www.hhmi.org/research/cell-cellcommunication-bacteria
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