Global regulators converge to orchestrate metabolism, biofilm, and pathogenesis

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Project Summary Diarrheal disease is a leading cause of morbidity and mortality in resource-poor areas. In order to colonize the intestine and cause disease, successful bacterial pathogens must sense and respond to intestinal signals by altering both metabolism and virulence factor expression. We hypothesize that by understanding the critical intestinal signals and the bacterial regulatory networks they activate, we can devise simple dietary alterations that prevent or mitigate morbidity and mortality. We focus on Vibrio cholerae, the agent of the severe diarrheal disease cholera. Because the metabolic pathways we study are highly conserved, these findings also serve as a paradigm for other bacteria that cause diarrhea. The goal of this work is to elucidate the complex and highly conserved regulatory network that is activated when V. cholerae enters the intestinal environment. In the first 4-year funding period of this grant, we explored the role of a global regulator of metabolism and virulence known as glucose-specific Enzyme llA. We showed that this regulator is membrane-associated through an N-terminal amphipathic helix and that membrane association is critical for its interaction with integral membrane protein partners that it regulates. Based on this work, we hypothesize that the inner membrane of the bacterial cell may act as a platform for regulatory proteins that sense and respond to nutritional signals in the intestinal environment. During the previous funding period, we discovered that the subcellular location of the global transcription factor, the cAMP receptor protein (CRP), is regulated in response to environmental conditions. In the current funding period, we propose to follow up on these observations by investigating regulation of CRP subcellular localization, the mechanism by which subcellular localization alters CRP activation of gene transcription, and the functional significance of CRP subcellular localization for V. cholerae virulence. We hypothesize that if the subcellular localization of CRP can be controlled via host diet, it may be possible to reduce pathogen virulence and thereby the morbidity and mortality caused by cholera.