Lotoux Aurélie, Caulat Léo, Martins Alves Catarina, Alves Feliciano Carolina, Morvan Claire, Folgosa Filipe, Martin-Verstraete Isabelle
Institut Pasteur, Université Paris Cité, UMR CNRS 6047, Laboratoire Pathogenèse des Bactéries Anaérobies, Paris, Île-de-France, France.
Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Lisbon, Portugal.
mBio. 2025 Apr 9;16(4):e0375324. doi: 10.1128/mbio.03753-24. Epub 2025 Mar 20.
, a strict anaerobe, is the major cause of antibiotic-associated diarrhea. This enteropathogen must adapt to oxidative stress mediated by reactive oxygen species (ROS), notably those released by the neutrophils and macrophages recruited to the site of infection or those endogenously produced upon high oxygen (O) exposure. uses a superoxide reductase, Sor, and several peroxidases to detoxify ROS. We showed that Sor has a superoxide reductase activity and protects the bacterium from exposure to menadione, a superoxide donor. After confirming the peroxidase activity of the rubrerythrin, Rbr, we showed that this enzyme together with the peroxiredoxin, Bcp, plays a central role in the detoxification of HO and promotes the survival of in the presence of not only HO but also air or 4% O. Under high O concentrations encountered in the gastrointestinal tract, the bacterium generated endogenous HO. The two O reductases, RevRbr2 and FdpF, have also a peroxidase activity and participate in HO resistance. The gene, which also contributes to HO protection, forms an operon with , , and encoding a HO-sensing repressor. The expression of the genes encoding the ROS reductases and the CD0828 protein was induced upon exposure to either HO or air. We showed that the induction of the operon is mediated not only by PerR but also by OseR, a recently identified O-responsive regulator of , and indirectly by σ, the sigma factor of the stress response, whereas the expression of is only controlled by σ.
ROS plays a fundamental role in intestinal homeostasis, limiting the proliferation of pathogenic bacteria. is an important enteropathogen that induces an intense immune response, characterized by the massive recruitment of immune cells responsible for secreting ROS, mainly HO 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 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 survives under conditions of an exacerbated inflammatory response.
艰难梭菌是一种严格厌氧菌，是抗生素相关性腹泻的主要病因。这种肠道病原体必须适应由活性氧（ROS）介导的氧化应激，尤其是那些由招募到感染部位的中性粒细胞和巨噬细胞释放的ROS，或在高氧（O₂）暴露时内源性产生的ROS。艰难梭菌利用一种超氧化物还原酶Sor和几种过氧化物酶来解毒ROS。我们发现Sor具有超氧化物还原酶活性，并能保护该细菌免受超氧化物供体甲萘醌的暴露。在确认了红素氧还蛋白（Rbr）的过氧化物酶活性后，我们发现这种酶与过氧化物氧还蛋白（Bcp）一起，在H₂O₂解毒中起核心作用，并不仅在存在H₂O₂的情况下，而且在空气或4% O₂存在的情况下促进艰难梭菌的存活。在胃肠道中遇到的高O₂浓度下，该细菌会产生内源性H₂O₂。两种O₂还原酶RevRbr2和FdpF也具有过氧化物酶活性，并参与对H₂O₂的抗性。同样有助于H₂O₂保护的perR基因与编码一种H₂O₂感应阻遏物的cd0828、oscR和rbr基因形成一个操纵子。编码ROS还原酶和CD0828蛋白的基因在暴露于H₂O₂或空气时被诱导表达。我们发现perR操纵子的诱导不仅由PerR介导，还由最近鉴定出的艰难梭菌的O₂应答调节因子OseR介导，并间接由应激反应的σ因子介导，而oscR的表达仅由σ因子控制。
ROS在肠道内环境稳定中起基本作用，限制病原菌的增殖。艰难梭菌是一种重要的肠道病原体，可诱导强烈的免疫反应，其特征是大量招募负责分泌ROS（主要是H₂O₂和超氧化物）的免疫细胞。我们在这项研究中表明，ROS暴露会导致产生一系列参与ROS解毒的酶。这包括一种超氧化物还原酶和四种过氧化物酶，即Rbr、Bcp、RevRbr2和FdpF。这些酶可能有助于艰难梭菌营养细胞在宿主免疫反应期间在结肠中存活。对于编码ROS解毒酶的基因也观察到不同的调控，从而对ROS暴露的适应性反应进行精细调节。了解感染期间ROS保护机制可能有助于揭示艰难梭菌在炎症反应加剧的条件下如何存活。
