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.

http://www.hhmi.org/research/cell-cell-communication-bacteria

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

http://www.nature.com/nchembio/journal/v7/n8/full/nchembio.618.html?style=0

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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