Species-Specific Quorum Sensing Represses the Chitobiose Utilization Locus in Vibrio cholerae.

The marine facultative pathogen forms complex multicellular communities on the chitinous shells of crustacean zooplankton in its aquatic reservoir. -chitin interactions are critical for the growth, evolution, and waterborne transmission of cholera. This is due, in part, to chitin-induced changes in gene expression in this pathogen. Here, we sought to identify factors that influence chitin-induced expression of one locus, the chitobiose utilization operon (), which is required for the uptake and catabolism of the chitin disaccharide. Through a series of genetic screens, we identified that the master regulator of quorum sensing, HapR, is a direct repressor of the operon. We also found that the levels of HapR in are regulated by the ClpAP protease. Furthermore, we show that the canonical quorum sensing cascade in regulates expression in an HapR-dependent manner. Through this analysis, we found that signaling via the species-specific autoinducer CAI-1, but not the interspecies autoinducer AI-2, influences expression. This phenomenon of species-specific regulation may enhance the fitness of this pathogen in its environmental niche. In nature, bacteria live in multicellular and multispecies communities. Microbial species can sense the density and composition of their community through chemical cues using a process called quorum sensing (QS). The marine pathogen is found in communities on the chitinous shells of crustaceans in its aquatic reservoir. interactions with chitin are critical for the survival, evolution, and waterborne transmission of this pathogen. Here, we show that uses QS to regulate the expression of one locus required for -chitin interactions.