Abstract
Oxidative stress is a major challenge faced by bacteria. Many bacteria control oxidative stress resistance pathways through the transcriptional regulator OxyR. The human pathogen Vibrio cholerae is a Gram-negative bacterium that is the causative agent of cholera. V. cholerae lives in both aquatic environments and human small intestines, two environments in which it encounters reactive oxygen species (ROS). To study how V. cholerae responds to oxidative stress, we constructed an in-frame oxyR deletion mutant. We found that this mutant was not only sensitive to H2O2, but also displayed a growth defect when diluted in rich medium. Further study showed that two catalases, KatG and KatB, either when expressed in living cells, present in culture supernatants, or added as purified recombinant proteins, could rescue the oxyR growth defect. Furthermore, although it could colonize infant mouse intestines similar to that of wildtype, the oxyR mutant was defective in zebrafish intestinal colonization. Alternatively, co-infection with wildtype, but not katG-katB deletion mutants, greatly enhanced oxyR mutant colonization. Our study suggests that OxyR in V. cholerae is critical for antioxidant defense and that the organism is capable of scavenging environmental ROS to facilitate population growth.
Highlights
Oxidative stress, resulting from exposure to reactive oxygen species (ROS) which can damage proteins, DNA, and membranes, is a major challenge for all living organisms
This is not surprising since H2O2 is produced as an autoxidation product of aerobic rich broth [22] and OxyR is critically involved in oxidative stress resistance
Oxidative stress induced by reactive oxygen species (ROS) must be a common stress condition to which V. cholerae encounters
Summary
Oxidative stress, resulting from exposure to reactive oxygen species (ROS) which can damage proteins, DNA, and membranes, is a major challenge for all living organisms. Bacteria have developed antioxidant defense systems to deal with oxidative stress by synthesizing superoxide dismutase and catalase [2,3,4]. In most bacteria, these processes are controlled by the transcriptional activator OxyR, a member of the LysR family of transcriptional regulators [5]. Hydrogen peroxide H2O2 activates OxyR via cysteine modification or disulfide bond formation [6,7,8]. OxyR is widely conserved among both Gram-negative and Gram-positive bacteria and numerous homologs have been shown to regulate the oxidative stress response, and virulence, biofilm formation, and fimbrial synthesis [9]
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