Institute for Microbiology, Friedrich Schiller University, Philosophenweg 12, 07743 Jena, Germany.
Scienova GmbH, Spitzweidenweg 30, 07743 Jena, Germany.
FEMS Microbiol Ecol. 2018 Jan 1;94(1). doi: 10.1093/femsec/fix176.
Reductive dehalogenation of organohalides is carried out by organohalide-respiring bacteria (OHRB) in anoxic environments. The tetrachloroethene (PCE)-respiring Epsilonproteobacterium Sulfurospirillum multivorans is one of few OHRB able to respire oxygen. Therefore, we investigated the organism's capacity to dehalogenate PCE in the presence of oxygen, which would broaden the applicability to use S. multivorans, unlike other commonly oxygen-sensitive OHRB, for bioremediation, e.g. at oxic/anoxic interphases. Additionally, this has an impact on our understanding of the global halogen cycle. Sulfurospirillum multivorans performs dehalogenation of PCE to cis-1,2-dichloroethene at oxygen concentrations below 0.19 mg/L. The redox potential of the medium electrochemically adjusted up to +400 mV had no influence on reductive dehalogenation by S. multivorans in our experiments, suggesting that higher levels of oxygen impair PCE dechlorination by inhibiting or inactivating involved enzymes. The PCE reductive dehalogenase remained active in cell extracts of S. multivorans exposed to 0.37 mg/L oxygen for more than 96 h. Analysis of the proteome revealed that superoxide reductase and cytochrome peroxidase amounts increased with 5% oxygen in the gas phase, while the response to atmospheric oxygen concentrations involved catalase and hydrogen peroxide reductase. Taken together, our results demonstrate that reductive dehalogenation by OHRB is not limited to anoxic conditions.
有机卤化物的还原脱卤作用是在缺氧环境中由有机卤化物呼吸细菌（OHRB）进行的。四氯乙烯（PCE）呼吸的 ε-变形菌 Sulfurospirillum multivorans 是少数能够呼吸氧气的 OHRB 之一。因此，我们研究了该生物体在存在氧气的情况下脱卤化 PCE 的能力，这将拓宽使用 S. multivorans 的适用性，与其他通常对氧气敏感的 OHRB 不同，可用于生物修复，例如在好氧/缺氧界面。此外，这对我们理解全球卤素循环有影响。Sulfurospirillum multivorans 在氧气浓度低于 0.19 mg/L 时将 PCE 还原脱卤化为顺式-1,2-二氯乙烯。电化学调节至+400 mV 的介质氧化还原电位对 S. multivorans 的还原脱卤作用没有影响，这表明较高水平的氧气通过抑制或失活相关酶来损害 PCE 脱氯。在暴露于 0.37 mg/L 氧气超过 96 小时的 S. multivorans 细胞提取物中，PCE 还原脱卤酶仍然保持活性。对蛋白质组的分析表明，超氧化物还原酶和细胞色素过氧化物酶的量随着气相中 5%的氧气而增加，而对大气氧浓度的反应涉及过氧化氢酶和过氧化氢还原酶。总之，我们的结果表明，OHRB 的还原脱卤作用不仅限于缺氧条件。
