Distinct HO-Scavenging System in : KatG and AhpC Act Together to Scavenge Endogenous Hydrogen Peroxide.

To colonize in the digestive tract of animals and humans, has to deal with reactive oxygen species (ROS) produced by host cells and microbiota. However, an understanding of the ROS-scavenging systems and their regulation in this bacterium remains largely elusive. In this study, we identified OxyR as the master transcriptional regulator mediating cellular responses to hydrogen peroxide (HO) in through genomics and transcriptomics analyses. OxyR activates transcription of diverse genes, especially the core members of its regulon, including those encoding catalases, peroxidases, and thiol reductases. The data also suggest that sulfur species and manganese may play a particular role in the oxidative stress response of . Among the three HO-scavenging systems in , catalase/peroxidase KatE functions as the primary scavenger for high levels of HO; NADH peroxidase lkyl ydroeroxide eductase (AhpR) and catalase KatG together are responsible for removing low levels of HO. The simultaneous loss of both AhpC (the peroxidatic component of AhpR) and KatG results in activation of OxyR. Moreover, we found that AhpC, unlike its well-characterized counterpart, has little effect on protecting cells against toxicity of organic peroxides. These findings provide not only novel insights into the structural and functional diversity of bacterial HO-scavenging systems but also a basic understanding of how copes with oxidative stress.