Acyl-homoserine lactone quorum sensing in Gram-negative bacteria: A signaling mechanism involved in associations with higher organisms

Recent advances in studies of bacterial gene expression have brought the re alization that cell-to-cell communication and community behavior are critic al for successful interactions with higher organisms. Species-specific cell -to-cell communication is involved in successful pathogenic or symbiotic in teractions of a variety of bacteria with plant and animal hosts. One type o f cell-cell signaling is acyl-homoserine lactone quorum sensing in Gram-neg ative bacteria. This type of quorum sensing represents a dedicated communic ation system that enables a given species to sense when it has reached a cr itical population density in a host, and to respond by activating expressio n of genes necessary for continued success in the host. Acyl-homoserine lac tone signaling in the opportunistic: animal and plant pathogen Pseudomonas aeroginosa is a model for the relationships among quorum sensing, pathogene sis, and community behavior, In the P. aeroginosa model, quorum sensing is required for normal biofilm maturation and for virulence. There are multipl e quorum-sensing circuits that control the expression of dozens of specific genes that represent potential virulence loci.