Data_Sheet_1_The DmsABC S-oxide reductase is an essential component of a novel, hypochlorite-inducible system of extracellular stress defense in Haemophilus influenzae.DOCX

Defenses against oxidative damage to cell components are essential for survival of bacterial pathogens during infection, and here we have uncovered that the DmsABC S-/N-oxide reductase is essential for virulence and in-host survival of the human-adapted pathogen, Haemophilus influenzae. In several different infection models, H. influenzae ΔdmsA strains showed reduced immunogenicity as well as lower levels of survival in contact with host cells. Expression of DmsABC was induced in the presence of hypochlorite and paraquat, closely linking this enzyme to defense against host-produced antimicrobials. In addition to methionine sulfoxide, DmsABC converted nicotinamide- and pyrimidine-N-oxide, precursors of NAD and pyrimidine for which H. influenzae is an auxotroph, at physiologically relevant concentrations, suggesting that these compounds could be natural substrates for DmsABC. Our data show that DmsABC forms part of a novel, periplasmic system for defense against host-induced S- and N-oxide stress that also comprises the functionally related MtsZ S-oxide reductase and the MsrAB peptide methionine sulfoxide reductase. All three enzymes are induced following exposure of the bacteria to hypochlorite. MsrAB is required for physical resistance to HOCl and protein repair. In contrast, DmsABC was required for intracellular colonization of host cells and, together with MtsZ, contributed to resistance to N-Chlorotaurine. Our work expands and redefines the physiological role of DmsABC and highlights the importance of different types of S-oxide reductases for bacterial virulence.

细胞组分氧化损伤防御机制对于病原菌在感染过程中的存活至关重要。本研究揭示，DmsABC S-/N-氧化物还原酶（DmsABC S-/N-oxide reductase）对于人适应性病原菌流感嗜血杆菌（Haemophilus influenzae）的毒力与宿主体内存活能力不可或缺。在多种不同感染模型中，ΔdmsA流感嗜血杆菌菌株（H. influenzae ΔdmsA strains）的免疫原性显著降低，且与宿主细胞接触后的存活水平也明显下降。次氯酸盐（hypochlorite）与百草枯（paraquat）存在时可诱导DmsABC的表达，这将该酶与宿主产生的抗菌物质防御紧密关联起来。除甲硫氨酸亚砜外，DmsABC还可在生理相关浓度下催化烟酰胺N-氧化物与嘧啶N-氧化物的转化——这两类物质是NAD与嘧啶的前体，而流感嗜血杆菌对此类物质属于营养缺陷型（auxotroph），这提示上述化合物或为DmsABC的天然底物。本研究数据表明，DmsABC是一套全新的抵御宿主诱导的S-/N-氧化物胁迫的周质系统的组成部分，该系统还包含功能相关的MtsZ S-氧化物还原酶（MtsZ S-oxide reductase）与MsrAB肽基甲硫氨酸亚砜还原酶（MsrAB peptide methionine sulfoxide reductase）。上述三种酶均会在细菌暴露于次氯酸（HOCl）后被诱导表达。MsrAB是细菌抵御次氯酸损伤与蛋白质修复所必需的。与之相反，DmsABC是宿主细胞内定植所必需的，且与MtsZ协同参与抵御N-氯代牛磺酸（N-Chlorotaurine）的胁迫。本研究拓展并重新界定了DmsABC的生理功能，同时凸显了不同类型S-氧化物还原酶在细菌毒力中的重要性。