Distinct Roles of Shewanella oneidensis Thioredoxin in Regulation of Cellular Responses to Hydrogen and Organic Peroxides

摘要

The thioredoxin (Trx) and glutaredoxin (Grx) antioxidant systems are deeply involved in bacterial response to oxidative stress, but to date, we know surprisingly little about the roles of these systems in response to reactive oxygen species (ROS) other than hydrogen peroxide (H2O2). In this study, we used Shewanella oneidensis, an environmental bacterium, as a research model to investigate the roles of Trx and Grx in oxidative stress response because it has functionally intertwined ROS responsive regulators OxyR and OhrR. We found that Trx1 is the major thiol/disulfide redox system and that in its absence a Grx system becomes essential under normal conditions. Although overshadowed by Trx1 in the wild type, Trx2 can fully replace Trx1 in physiology when overproduced. Trx1 is required for OxyR to function as a repressor but, more importantly, plays a critical role in the cellular response to organic peroxide (OP) by mediating the redox status of OhrR but not OP scavenger OhrA. While none of the trx and grx genes are OxyR dependent, trxA and trxC are affected by OhrR indirectly. Additional data suggest that depletion of glutathione is likely the cue to trigger induced expression of trxA and trxC. These findings underscore the particular importance of Trx in the bacterial OP stress response.