Let LuxS speak up in al-2 signaling

Quorum sensing is a process of bacterial cell-cell communication that uses small diffusible molecules to coordinate diverse behaviors in response to population density. The only quorum-sensing system shared by Gram-positive and Gram-negative bacteria involves the production of autoinducer-2 (Al-2). The Al-2 synthase LuxS is widely distributed among the Bacteria, which suggests that Al-2 is a language for interspecies communication. However, LuxS is also an integral component of the activated methyl cycle in bacteria. LuxS-based quorum sensing has been intensively studied in the past decade, mostly in relation to the Al-2 molecule and the downstream effects of luxS knockouts; few studies have focused on the gene and protein activity itself. Ongoing attempts to dissect the metabolic and signaling roles of LuxS leave little doubt that unraveling the regulation of luxS expression and cellular LuxS activity is the key to understanding LuxS-based quorum sensing.