Modulation of CrbS-dependent activation of the acetate switch in Vibrio cholerae .

Vibrio cholerae controls the pathogenicity of interactions with arthropod hosts via the activity of the CrbS/R two component system. This signaling pathway regulates the consumption of acetate, which in turn, alters the relative virulence of interactions with arthropods, including Drosophila melanogaster CrbS is a histidine kinase that links a transporter-like domain to its signaling apparatus via putative STAC and PAS domains. CrbS and its cognate response regulator are required for expression of acetyl-CoA synthetase ( acs ), which converts acetate to acetyl-CoA. We demonstrate that the STAC domain of CrbS is required for signaling in culture; without it, acs transcription is reduced in LB medium, and V. cholerae cannot grow on acetate minimal media. However, the strain remains virulent towards Drosophila and expresses acs similarly to wild-type during infection. This suggests that there exists a unique signal or environmental variable that modulates CrbS in the gastrointestinal tract of Drosophila. Secondly, we present evidence in support of CrbR, the response regulator that interacts with CrbS, binding directly to the acs promoter, and we identify a region of the promoter that CrbR may target. We further demonstrate that nutrient signals, together with the CRP-cAMP system, control acs transcription, but regulation may occur indirectly, as CRP-cAMP activates expression of the crbS and crbR genes. Lastly, we define the role of the Pta-AckA system in V. cholerae, and identify redundancy built into acetate excretion pathways in this pathogen. Importance CrbS is a member of a unique family of sensor histidine kinases, as its structure suggests that it may link signaling to transport of a molecule. However, mechanisms through which CrbS senses and communicates information about the outside world are unknown. In the Vibrionaceae , orthologs of CrbS regulate acetate metabolism, which can, in turn, affect interactions with host organisms. Here, we situate CrbS within a larger regulatory framework, demonstrating that crbS is regulated by nutrient sensing systems. Furthermore, CrbS domains may play varying roles in signaling during infection and growth in culture, suggesting a unique mechanism of host recognition. Lastly, we define the roles of additional pathways in acetate flux, as a foundation for further studies of this metabolic nexus point.