Bacterial cell-to-cell signaling, termed quorum sensing, has emerged as a new field in microbiology. Individual bacteria use chemical signals to communicate with each other and coordinate group activities. The best understood signaling system employs diffusable acyl-homoserine lactone (acyl-HSL) molecules that are made by an acyl-HSL synthase and are bound by a cognate receptor that acts as a transcriptional activator. There are now over 70 known examples of such components in bacterial species. The opportunistic human pathogen Pseudomonas aeruginosa serves as a model system to study quorum sensing gene regulation. It employs at least two acyl-HSL signaling systems to control the expression of two large, overlapping sets of target genes. In addition to its function as a global regulator of gene expression, quorum sensing in P. aeruginosa is also important for virulence and the formation of biofilms, surface-associated bacterial communities, which have been implicated in chronic persistent infection. As such, quorum sensing has become an important target for antimicrobial and antibiofilm strategies.
