Bile Salts and N-Acetyl-D-Glucosamine induce transcription of the vieSAB Operon in Vibrio cholerae El Tor

The vieSAB operon regulates motility, biofilm formation and cholera toxin production in the classical biotype of V. cholerae . Classical biotype mutants lacking the cyclic-di-GMP phosphodiesterase and response regulator vieA or its cognate sensor kinase vieS fail to effectively colonize the infant mouse small intestine, are less motile than the wild-type strain, and are hyper-biofilm formers. However, deletion of vieA or vieS in the currently-circulating El Tor biotype does not have a demonstrable effect on these phenotypes. To begin to understand the role of vieSAB in the El Tor biotype, we studied its regulation and the effect of vieA expression on bacterial physiology, separating the functional roles of VieA’s enzymatic and DNA-binding activities. We identify bile salts and N-acetylglucosamine, which can be found at high concentration in the small intestine, as stimulating expression of vieSAB during in vitro growth. We show that, in contrast to many response regulators, VieA does not regulate its own expression. Together, these data indicate that V. cholerae upregulates vieSAB in response to small-intestinal signals, allowing VieA to alter the physiology of the cell through its transcriptional regulation and cyclic-di-GMP signaling activities in order to adapt to the human host. ### Competing Interest Statement The authors have declared no competing interest.