Regulatory circuits and communication in Gram-negative bacteria

It is increasingly apparent that, in nature, bacteria function less as individuals and more as coherent groups that are able to inhabit multiple ecological niches. The increased awareness of the role of cell–cell communication in the ecology of Gram-negative bacteria is matched by an understanding of both the physiology and the molecular biology that underlie this process. In particular, the regulatory circuits and the structure of one of the important regulatory proteins have recently been described. Here, we review the current understanding of quorum-sensing circuits in bacteria, and the role of the regulatory LuxR-type proteins in particular.