Keywords: cell-cell communication, symbiosis, autoinducers, lux system, V fischeri, P aeuroginosa, quorum sensing
Technical note: Quorum sensing
Quorum sensing, or the control of gene expression in response to cell density, is used by both gram negative and gram positive bacteria to regulate a variety of physiological functions including bioluminescence, swarming, antibiotic biosynthesis, plasmid conjugal transfer and the production of virulence determinants in animal, fish and plant pathogens. In all cases, quorum sensing involves the production and detection of extra cellular signalling molecules called "auto inducers". In gram negative bacteria, acyl-homoserine lactone molecules (AHL) serve as the main signalling molecules, whereas in gram positive bacteria, peptides or modified peptides serve as the primary means of signalling. Whilst universal signalling themes exist, variations in the design of the extra cellular signals, the signal detection apparatus and the biochemical mechanisms of signal relay have allowed quorum sensing systems to be exquisitely adopted for their varied uses. Quorum sensing also offers the possibility of new therapeutic strategies for the control of infections. Recent studies show that quorum sensing modulates both intra and inter species cell-cell communication and it plays a major role in enabling bacteria to architect complex community structure.