Quorum Sensing
http://www.ted.com/talks/bonnie_bassler_on_how_bacteria_communicate
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 “free-
dwellers” 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-cell-communication-bacteria
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