The ArcA Mutation In Shewanella Oneidensis Causes A Mechanism Of Action Of Increased Hydrogen Peroxide Sensitivity

Oxidative stress is one of the major challenges that Shewanella encounter routinely because they thrive in redox-stratified environments prone to reactive oxygen species (ROS) formation. In this group of bacteria as typified in the model species S. oneidensis, two main oxidative response specific regulators OxyR and OhrR are functionally intertwined; both are able to sense and respond to H2O2 and organic peroxides. In our efforts to unveil the involvement of global regulators for respiration in the oxidative stress response, we found that the Arc system confers S. oneidensis resistance to H2O2 whereas neither Fnr nor Crp has a significant role. A comparison of transcriptomic profiles of the wild-type and its isogenic arcA mutant revealed that the OxyR regulon is independent of the Arc system. We then provided evidence to suggest that the H2O2 hypersensitivity of the arcA mutant is due to the increased H2O2 uptake rate, a result of a cell envelope defect. Although one of three proteases of the ArcA regulon when in excess is partially accountable for the envelope defect, the major contributors remain elusive. Overall, our data indicate that the Arc system influences the bacterial physiology through a novel mechanism that has not been reported before.