How bacteria talk to each other: regulation of gene expression by quorum sensing

Quorum sensing, or the control of gene expression in response to cell densi ty, is used by both Gram-negative and Gram-positive bacteria to regulate a variety of physiological functions. In all cases, quorum sensing involves t he production and detection of extracellular signalling molecules called au toinducers. While universal signalling themes exist, variations in the desi gn of the extracellular signals, the signal detection apparatuses, and the biochemical mechanisms of signal relay have allowed quorum sensing systems to be exquisitely adapted for their varied uses. Recent studies show that q uorum sensing modulates both intra- and inter-species cell-cell communicati on, and it plays a major role in enabling bacteria to architect complex com munity structures.