Paracrine Parable

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Science  07 Aug 2009:
Vol. 325, Issue 5941, pp. 656
DOI: 10.1126/science.325_656d
CREDIT: LOPEZ ET AL., GENES DEV. 23, 1631 (2009)

Bacillus subtilis is a soil-dwelling organism that forms biofilms—extracellular matrices harboring a bacterial community. One way in which bacteria are known to coordinate their activities is via signaling molecules that are produced when the colony reaches a certain density, a phenomenon known as quorum sensing. Lopez et al. describe a distinct mode of social networking, referred to as paracrine signaling. Many of the cells in a B. subtilis biofilm secrete a small peptide called ComX. This peptide binds to a membrane-bound kinase and triggers the phosphorylation of an intracellular transcription factor, which goes on to initiate the synthesis and secretion of the peptide surfactin in a small group of cells. The authors have discovered that apart from being a surfactant, surfactin evokes extracellular matrix production in another group of cells. Surfactin producers do not make extracellular matrix themselves, whereas matrix producers do not become surfactin producers, because their response to ComX is blocked by the presence of matrix. Thus, populations of independently minded cells develop and coexist for prolonged periods, alongside others with yet other functions, defying the notion that bacterial cells cannot differentiate and specialize like eukaryotic cells do.

Genes Dev. 23, 1631 (2009).

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