Quorum Sensing in Gram-Negative Bacteria

It has become increasingly and widely recognised that bacteria do not live as isolated entities but instead exist as communities that exploit elaborate systems of intercellular communication to facilitate their adaptation to changing environmental conditions. A well-characterised example of such intercellular communication is quorum sensing. Quorum sensing depends on the production of diffusible signal molecules termed autoinducers or pheromones, which enable a bacterium to monitor its own cell population density. A variety of physiological processes in a range of bacterial species is regulated by quorum sensing. Examples include bioluminescence, antibiotic biosynthesis, swarming, biofilm differentiation, conjugation and the production of virulence determinants in animal, fish and plant pathogens. The best studied common signalling molecules found in Gram-negative bacteria are N-acyl derivatives of homoserine lactone (acyl HSLs). In this paper, the current state of research concerning acyl HSL-mediated quorum sensing in Gram-negative bacteria is reviewed.