title: Quorum sensing and policing of Pseudomonas aeruginosa social cheaters.
abstract: The bacterium Pseudomonas aeruginosa is an opportunistic human pathogen that uses a quorum sensing signal cascade to activate expression of dozens of genes when sufficient population densities have been reached. Quorum sensing controls production of several key virulence factors, including secreted proteases such as elastase. Cooperating groups of bacteria growing on protein are susceptible to social cheating by quorum-sensing defective mutants. A possible way to restrict cheater emergence is by policing where cooperators produce costly goods to sanction or punish cheats. The P. aeruginosa LasR-LasI quorum sensing system controls genes including those encoding proteases and also those encoding a second quorum-sensing system, the RhlR-RhlI system, which controls numerous genes including those for cyanide production. By using RhlR quorum sensing mutants and cyanide synthesis mutants, we show that cyanide production is costly and cyanide-producing cooperators use cyanide to punish LasR-null social cheaters. Cooperators are less susceptible to cyanide than are LasR mutants. These experiments demonstrate policing in P. aeruginosa, provide a mechanistic understanding of policing, and show policing involves the cascade organization of the two quorum sensing systems in this bacterium.
authors: School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, ZJ 310012, China; Department of Microbiology, University of Washington, Seattle, WA 98195-7735; and.
authors: Meizhen
authors: M
authors: Wang
authors: Department of Microbiology, University of Washington, Seattle, WA 98195-7735; and.
authors: Amy L
authors: AL
authors: Schaefer
authors: Department of Microbiology, University of Washington, Seattle, WA 98195-7735; and Department of Medicine, University of Washington, Seattle, WA 98195.
authors: Ajai A
authors: AA
authors: Dandekar
authors: Department of Microbiology, University of Washington, Seattle, WA 98195-7735; and epgreen@uw.edu.
authors: E Peter
authors: EP
authors: Greenberg
mesh_terms: D003486:Cyanides / Q000378:metabolism; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D053038:Quorum Sensing; D014774:Virulence
chemical_list: D003486:Cyanides
keywords: bacterial communication; cooperation; social evolution; sociomicrobiology
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