Date of Award

2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Biology

First Advisor

Jun Zhu

Second Advisor

Mark Goulian

Abstract

Vibrio cholerae, the causative agent of the infectious disease, cholera, is a water-borne pathogen with a dynamic lifestyle across physical environments of different oxygen levels with various sources of oxidative stress. The anaerobic respiratory control (ArcB/A) two-component system is a global regulator that facilitates the transition between different electron transport strategies with respect to the redox environment. Upon sensing a more anoxic quinone pool at the inner membrane, the histidine kinase ArcB activates the response regulator ArcA’s regulatory functions by phosphorylation. ArcA has been reported in Escherichia coli and Salmonella enterica to be important for oxidative stress resistance, yet the mechanism through which ArcA respond to this stress is unknown. Here we report ArcA’s regulatory functions being partially retained in V. cholerae upon oxidative stress. This additional redox-sensing under oxidative stress is dependent on a cysteine residue, C173, in ArcA’s C-terminal DNA-binding domain. C173 is crucial in sustaining in vitro oxidative stress challenges and during colonization of mouse intestines. Phosphorylation state analysis indicates that ArcA phosphorylation is compromised when V. cholerae is challenged by oxidative stress. In vitro biochemical assays reveal that C173- dependent oxidation initiates ArcA binding to DNA containing an ArcA-binding motif. C173- dependent oxidation also promotes ArcA-ArcA interaction, similar to the effect from a microaerobic induction of ArcA. ArcA C173 is conserved in various Gram-negative pathogens. In vitro oxidative stress challenges and human intestinal epithelial cell invasion experiments with S. enterica further underscore the importance of ArcA C173 for bacterial survival. This work uncovers a new post-translational modification, oxidation, in addition to phosphorylation, that serves as an activating signal for ArcA. The redox response from ArcA couples a stress response to other ArcA-mediated transitions for an adaptation to a new environment, demonstrating theintricacy of bacterial stress responses and their close association to basic energy metabolism.

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