Defense arsenal of the strict anaerobe <i>Clostridioides difficile</i> against reactive oxygen species encountered during its infection cycle

ROS plays a fundamental role in intestinal homeostasis, limiting the proliferation of pathogenic bacteria. <i>Clostridioides difficile</i> is an important enteropathogen that induces an intense immune response, characterized by the massive recruitment of immune cells responsible for secreting ROS, mainly H₂O₂ and superoxide. We showed in this work that ROS exposure leads to the production of an armada of enzymes involved in ROS detoxification. This includes a superoxide reductase and four peroxidases, Rbr, Bcp, revRbr2, and FdpF. These enzymes likely contribute to the survival of vegetative cells of <i>C. difficile</i> in the colon during the host immune response. Distinct regulations are also observed for the genes encoding the ROS detoxification enzymes allowing a fine tuning of the adaptive response to ROS exposure. Understanding the mechanisms of ROS protection during infection could shed light on how <i>C. difficile</i> survives under conditions of an exacerbated inflammatory response.