Department of Medical Microbiology, Medical University of Sofia, 2 Zdrave Str., 1431, Sofia, Bulgaria.
Department of Medical Microbiology, Medical University of Sofia, 2 Zdrave Str., 1431, Sofia, Bulgaria.
Anaerobe. 2024 Oct;89:102897. doi: 10.1016/j.anaerobe.2024.102897. Epub 2024 Aug 21.
Oxygen tolerance of anaerobes is a virulence factor, but can also be a beneficial property. Many species have evolved to tolerate or take advantage of the presence of low, especially nanaerobic (≤0.14 %) oxygen concentrations. Oxygen tolerance is genus-, species- and strain-dependent according to their protective mechanisms. It was better expressed in some pathogenic species such as Bacteroides fragilis, Clostridioides difficile, and Clostridium perfringens, as well as in Akkermansia muciniphila than in other potential probiotics such as Alistipes, Blautia and Roseburia spp. Different degrees of oxygen sensitivity were found between the strains of Anaerostipes, Faecalibacterium, and Bifidobacterium spp. Importantly, clostridial spores and anaerobes in biofilms are protected from oxidation. Rubrerythrins and flavodiiron proteins and two regulators (sigma factor B and PerR) contribute to C. difficile protection from reactive oxygen species (ROS). The frequent pathogen, B. fragilis, has numerous protective factors such as enzymes (catalase, superoxide dismutase, alkyl hydroperoxidase, thioredoxin peroxidase, and aerobic-type NrdAB ribonucleotide reductase), and nanaerobic respiration. Seven proteins confer strain-specific oxygen adaptation of Faecalibacterium prausnitzii. Oxygen tolerance protects anaerobes from ROS, shields their DNA and modulates gene expression. Furthermore, oxygen can induce mutations leading to antibiotic resistance as shown in Prevotella melaninogenica. Some Faecalibacterium, Anaerostipes, Bifidobacterium, and Akkermansia strains from the intestinal microbiota exhibiting oxygen tolerance may become next-generation probiotic candidates. Further studies are needed to reveal oxygen effects on more anaerobic species and strains, and the influence of oxygen on antibiotic resistance. More studies on oxygen-tolerant probiotic strains can be useful to optimize biotechnological methods.
厌氧菌的耐氧性是一种毒力因子，但也可能是一种有益的特性。许多物种已经进化到可以耐受或利用低氧，特别是无氧（≤0.14%）浓度的氧气。根据其保护机制，耐氧性取决于属、种和菌株。在一些致病物种中，如脆弱拟杆菌、艰难梭菌和产气荚膜梭菌，以及阿克曼氏菌，比其他潜在的益生菌，如拟杆菌属、布劳特氏菌属和罗氏菌属，表达得更好。在产丁酸菌属、真杆菌属和双歧杆菌属的菌株之间发现了不同程度的氧敏感性。重要的是，梭菌孢子和生物膜中的厌氧菌免受氧化。Rubrerythrins 和黄素铁蛋白以及两个调节因子（sigma 因子 B 和 PerR）有助于艰难梭菌抵抗活性氧（ROS）。频繁的病原体脆弱拟杆菌具有许多保护因子，如酶（过氧化氢酶、超氧化物歧化酶、烷烃过氧化物酶、硫氧还蛋白过氧化物酶和需氧型 NrdAB 核糖核苷酸还原酶）和无氧呼吸。七种蛋白质赋予粪肠球菌特定于菌株的氧气适应能力。耐氧性保护厌氧菌免受 ROS 侵害，保护其 DNA 并调节基因表达。此外，正如在黑色素普雷沃氏菌中所显示的那样，氧气可以诱导导致抗生素耐药性的突变。一些来自肠道微生物群的粪肠球菌、产丁酸菌属、双歧杆菌属和阿克曼氏菌属的菌株具有耐氧性，可能成为下一代益生菌候选者。需要进一步的研究来揭示氧气对更多厌氧菌和菌株的影响，以及氧气对抗生素耐药性的影响。更多关于耐氧益生菌菌株的研究可能有助于优化生物技术方法。
