Oh Euna, McMullen Lynn, Jeon Byeonghwa
School of Public Health, University of Alberta, Edmonton, AB Canada.
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB Canada.
Front Microbiol. 2015 Apr 10;6:295. doi: 10.3389/fmicb.2015.00295. eCollection 2015.
Campylobacter jejuni, a microaerophilic foodborne pathogen, inescapably faces high oxygen tension during its transmission to humans. Thus, the ability of C. jejuni to survive under oxygen-rich conditions may significantly impact C. jejuni viability in food and food safety as well. In this study, we investigated the impact of oxidative stress resistance on the survival of C. jejuni under aerobic conditions by examining three mutants defective in key antioxidant genes, including ahpC, katA, and sodB. All the three mutants exhibited growth reduction under aerobic conditions compared to the wild-type (WT), and the ahpC mutant showed the most significant growth defect. The CFU reduction in the mutants was recovered to the WT level by complementation. Higher levels of reactive oxygen species were accumulated in C. jejuni under aerobic conditions than microaerobic conditions, and supplementation of culture media with an antioxidant recovered the growth of C. jejuni. The levels of lipid peroxidation and protein oxidation were significantly increased in the mutants compared to WT. Additionally, the mutants exhibited different morphological changes under aerobic conditions. The ahpC and katA mutants developed coccoid morphology by aeration, whereas the sodB mutant established elongated cellular morphology. Compared to microaerobic conditions, interestingly, aerobic culture conditions substantially induced the formation of coccoidal cells, and antioxidant treatment reduced the emergence of coccoid forms under aerobic conditions. The ATP concentrations and PMA-qPCR analysis supported that oxidative stress is a factor that induces the development of a viable-but-non-culturable state in C. jejuni. The findings in this study clearly demonstrated that oxidative stress resistance plays an important role in the survival and morphological changes of C. jejuni under aerobic conditions.
空肠弯曲菌是一种微需氧的食源性病原体，在传播给人类的过程中不可避免地会面临高氧张力。因此，空肠弯曲菌在富氧条件下的存活能力可能会对其在食品中的生存能力以及食品安全产生重大影响。在本研究中，我们通过检测三个关键抗氧化基因（包括ahpC、katA和sodB）存在缺陷的突变体，研究了抗氧化应激能力对空肠弯曲菌在有氧条件下生存的影响。与野生型（WT）相比，所有这三个突变体在有氧条件下均表现出生长减缓，其中ahpC突变体表现出最显著的生长缺陷。通过互补作用，突变体中的菌落形成单位（CFU）减少恢复到了野生型水平。与微需氧条件相比，空肠弯曲菌在有氧条件下积累了更高水平的活性氧，并且在培养基中添加抗氧化剂可恢复空肠弯曲菌的生长。与野生型相比，突变体中的脂质过氧化和蛋白质氧化水平显著升高。此外，突变体在有氧条件下表现出不同的形态变化。ahpC和katA突变体通过通气形成球状形态，而sodB突变体则形成细长的细胞形态。有趣的是，与微需氧条件相比，有氧培养条件显著诱导了球状细胞的形成，而抗氧化剂处理减少了有氧条件下球状形态的出现。ATP浓度和PMA-qPCR分析支持氧化应激是诱导空肠弯曲菌进入活的非可培养状态的一个因素。本研究结果清楚地表明，抗氧化应激能力在空肠弯曲菌在有氧条件下的生存和形态变化中起着重要作用。
