Microbiology

Controlling Death in Biofilms

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Science  08 Aug 2003:
Vol. 301, Issue 5634, pp. 737
DOI: 10.1126/science.301.5634.737a

Biofilms are not just a smear of slime and bacteria; they are complex and differentiated communities with a definite structure of columns and channels. Pseudomonas aeruginosa is a bacterium of considerable clinical notoriety and experimental interest that produces a lot of extracellular polysaccharide and alginate and that forms well-defined biofilms. Once attached to a surface, the bacteria often show a developmental sequence involving cell-cell signaling and the production of rhamnolipid surfactants that help to maintain free-flowing water channels.

Webb et al. have dissected the multicellular nature of biofilm development and discovered that a key component of biofilm architecture is programmed cell death, or autolysis. After a week in a glass flow cell reactor, patches of dead cells became apparent within the microcolonies lying in the biofilm. Like the events in fruiting body formation in social bacteria, such as Myxococcus, the transcription factor RpoN also controls cell death in P. aeruginosa. Death occurs via a combination of the las and rhl cell-signaling circuits, which use acylated homoserine lactones, and by flagellum-mediated bacteriophage infection. — CA

J. Bacteriol. 185, 4585 (2003

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