CAREER: Convergent molecular mechanisms regulating dormancy in Vibrios

Under unfavorable conditions such as starvation or antibiotic exposure, numerous microorganisms enter dormant states that facilitate their survival. Dormant bacterial cells have been linked to the failure of antibiotic therapy, food-related outbreaks, and environmental disease transmission. Despite the prevalence and biological significance of dormant states, several aspects of these critical phenomenon remain obscure. In this research project, the regulatory networks controlling bacterial dormancy and environmental conditions driving this phenomenon will be investigated. In this research project, Vibrio cholerae, the causative agent of cholera, will be used as a model system to study the role of a transcription factor, ToxR, in dormancy. However, the experimental approaches and potential findings will be applicable to numerous microorganisms that form these types of dormant cells. Results from this proposal may have major public health and economic implications as these cells are typically resistant to antibiotics and are a major source of food and water contamination. A major integrated education initiative, the Synergy Scholars Program, will foster the retention of underrepresented students in Biomedical Sciences at University of Central Florida, a large Hispanic-Serving Institution by creating a supportive community that revolves around the mentoring of scholars. A bridge program for students from the Universidad Interamericana de Puerto Rico (Aguadilla) to perform research at UCF in areas covered in this proposal and an updated course on "Bacterial Stress Responses" at UCF that will include topics from this proposal such as bacterial dormancy will be implemented. This research project focuses on the convergent regulatory networks controlling bacterial dormancy and how diverse environmental conditions drive this phenomenon. Aside from sporulation, there are two major states of dormant bacterial cells, persisters and viable but non-culturable (VBNC). Persister cells are typically selected after antibiotic exposure, whereas VBNC cells arise in natural environments due to exposure to biotic and abiotic factors. In spite of these differences, there are major overlaps between the two states. In this research project, the hypothesis that VBNC entry and persister cell formation are initiated by distinct stimuli but converge into common regulatory pathways will be tested using Vibrio cholerae as a model system and the master regulator ToxR. The main hypothesis will be tested in three independent but complementary aims: aim 1 will address how common aquatic abiotic and biotic drivers synergistically regulate VBNC in a ToxR-dependent manner via the stringent response; aim 2 will define the roles of ToxR and the cell envelope stress response in the regulation of persister cell formation; and, aim 3 will examine the role of a ToxR-regulated small RNA in the convergence of these dormant phenotypes. Overall, the use of genetic tools in a tractable model system and the integration of data on the regulatory networks and environmental conditions will provide insight into the dynamics of dormant cells. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.