Wan Fen, Mao Yinting, Dong Yangyang, Ju Lili, Wu Genfu, Gao Haichun
Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
Sci Rep. 2015 May 15;5:10228. doi: 10.1038/srep10228.
Oxidative stress is one of the major challenges that Shewanella encounter routinely because they thrive in redox-stratified environments prone to reactive oxygen species (ROS) formation, letting alone that ROS can be generated endogenously. As respiration is the predominant process for endogenous ROS, regulators mediating respiration have been demonstrated and/or implicated to play a role in oxidative stress response. In our efforts to unveil the involvement of global regulators for respiration in the oxidative stress response, we found that loss of the Arc system increases S. oneidensis sensitivity to H2O2 whereas neither Fnr nor Crp has a significant role. A comparison of transcriptomic profiles of the wild-type and its isogenic arcA mutant revealed that the OxyR regulon is independent of the Arc system. We then provided evidence that the enhanced H2O2 sensitivity of the arcA mutant is due to an increased H2O2 uptake rate, a result of a cell envelope defect. Although one of three proteases of the ArcA regulon when in excess is partially accountable for the envelope defect, the major contributors remain elusive. Overall, our data indicate that the Arc system influences the bacterial cell envelope biosynthesis, a physiological aspect that has not been associated with the regulator before.
氧化应激是希瓦氏菌经常遇到的主要挑战之一，因为它们在易于形成活性氧（ROS）的氧化还原分层环境中茁壮成长，更不用说ROS可以内源性产生。由于呼吸作用是内源性ROS的主要产生过程，介导呼吸作用的调节因子已被证明和/或暗示在氧化应激反应中发挥作用。在我们努力揭示呼吸作用的全局调节因子在氧化应激反应中的作用时，我们发现Arc系统的缺失增加了嗜铁钩端螺旋菌对H2O2的敏感性，而Fnr和Crp均无显著作用。对野生型及其同基因arcA突变体的转录组图谱进行比较后发现，OxyR调控子独立于Arc系统。然后我们提供证据表明，arcA突变体对H2O2敏感性增强是由于H2O2摄取速率增加，这是细胞包膜缺陷的结果。虽然ArcA调控子的三种蛋白酶之一过量时部分导致了包膜缺陷，但其主要原因仍不清楚。总体而言，我们的数据表明Arc系统影响细菌细胞包膜生物合成，这是一个以前未与该调节因子相关联的生理方面。
