Kassem Issmat I, Khatri Mahesh, Sanad Yasser M, Wolboldt Melinda, Saif Yehia M, Olson Jonathan W, Rajashekara Gireesh
Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio.
Microbiologyopen. 2014 Apr;3(2):168-81. doi: 10.1002/mbo3.158. Epub 2014 Feb 7.
The methylmenaquinol:fumarate reductase (Mfr) of Campylobacter jejuni is a periplasmic respiratory (redox) protein that contributes to the metabolism of fumarate and displays homology to succinate dehydrogenase (Sdh). Since chemically oxidized redox-enzymes, including fumarate reductase and Sdh, contribute to the generation of oxidative stress in Escherichia coli, we assessed the role of Mfr in C. jejuni after exposure to hydrogen peroxide (H2 O2 ). Our results show that a Mfr mutant (∆mfrA) strain was less susceptible to H2 O2 as compared to the wildtype (WT). Furthermore, the H2 O2 concentration in the ∆mfrA cultures was significantly higher than that of WT after exposure to the oxidant. In the presence of H2 O2 , catalase (KatA) activity and katA expression were significantly lower in the ∆mfrA strain as compared to the WT. Exposure to H2 O2 resulted in a significant decrease in total intracellular iron in the ∆mfrA strain as compared to WT, while the addition of iron to the growth medium mitigated H2 O2 susceptibility and accumulation in the mutant. The ∆mfrA strain was significantly more persistent in RAW macrophages as compared to the WT. Scanning electron microscopy showed that infection with the ∆mfrA strain caused prolonged changes to the macrophages' morphology, mainly resulting in spherical-shaped cells replete with budding structures and craters. Collectively, our results suggest a role for Mfr in maintaining iron homeostasis in H2 O2 stressed C. jejuni, probably via affecting the concentrations of intracellular iron.
富马酸还原酶（Mfr）是一种周质呼吸（氧化还原）蛋白，它有助于富马酸的代谢，并且与琥珀酸脱氢酶（Sdh）具有同源性。由于包括富马酸还原酶和Sdh在内的化学氧化还原酶会导致大肠杆菌中氧化应激的产生，我们评估了暴露于过氧化氢（H2O2）后Mfr在空肠弯曲菌中的作用。我们的结果表明，与野生型（WT）相比，Mfr突变体（∆mfrA）菌株对H2O2的敏感性较低。此外，暴露于氧化剂后，∆mfrA培养物中的H2O2浓度明显高于WT。在存在H2O2的情况下，与WT相比，∆mfrA菌株中的过氧化氢酶（KatA）活性和katA表达明显较低。与WT相比，暴露于H2O2导致∆mfrA菌株中细胞内总铁含量显著降低，而在生长培养基中添加铁可减轻突变体对H2O2的敏感性和积累。与WT相比，∆mfrA菌株在RAW巨噬细胞中的持续存在时间明显更长。扫描电子显微镜显示，用∆mfrA菌株感染会导致巨噬细胞形态发生长期变化，主要导致细胞呈球形，充满芽状结构和坑洼。总的来说，我们的结果表明Mfr在维持H2O2应激的空肠弯曲菌中铁稳态方面发挥作用，可能是通过影响细胞内铁的浓度来实现的。
