Doukyu Noriyuki, Taguchi Katsuya
Department of Life Science, Toyo University, 1-1-1 Izumino, Itakura-machi, Gunma, 374-0193, Japan.
Bio-Nano Electronic Research Center, Toyo University, 2100, Kujirai, Kawagoe, Saitama, 350-8585, Japan.
AMB Express. 2021 Jun 29;11(1):97. doi: 10.1186/s13568-021-01258-w.
Escherichia coli strains are generally sensitive to hydrophobic organic solvents such as n-hexane and cyclohexane. Oxidative stress in E. coli by exposure to these hydrophobic organic solvents has been poorly understood. In the present study, we examined organic solvent tolerance and oxygen radical generation in E. coli mutants deficient in reactive oxygen species (ROS)-scavenging enzymes. The organic solvent tolerances in single gene mutants lacking genes encoding superoxide dismutase (sodA, sodB, and sodC), catalase (katE and katG), and alkyl hydroperoxide reductase (ahpCF) were similar to that of parent strain BW25113. We constructed a BW25113-based katE katG double mutant (BW25113∆katE∆katG) and sodA sodB double mutant (BW25113sodA∆sodB). These double-gene mutants were more sensitive to hydrophobic organic solvents than BW25113. In addition, the intracellular ROS levels in E. coli strains increased by the addition of n-hexane or cyclohexane. The ROS levels in BW25113∆katE∆katG and BW25113∆sodA∆sodB induced by exposure to the solvents were higher than that in BW25113. These results suggested that ROS-scavenging enzymes contribute to the maintenance of organic solvent tolerance in E. coli. In addition, the promoter activities of sodA and sodB were significantly increased by exposure to n-hexane.
大肠杆菌菌株通常对疏水性有机溶剂如正己烷和环己烷敏感。关于暴露于这些疏水性有机溶剂下大肠杆菌的氧化应激情况，人们了解甚少。在本研究中，我们检测了缺乏活性氧（ROS）清除酶的大肠杆菌突变体对有机溶剂的耐受性以及氧自由基的产生。缺乏编码超氧化物歧化酶（sodA、sodB和sodC）、过氧化氢酶（katE和katG）和烷基过氧化氢还原酶（ahpCF）基因的单基因突变体对有机溶剂的耐受性与亲本菌株BW25113相似。我们构建了基于BW25113的katE katG双突变体（BW25113∆katE∆katG）和sodA sodB双突变体（BW25113sodA∆sodB）。这些双基因突变体对疏水性有机溶剂比BW25113更敏感。此外，添加正己烷或环己烷会使大肠杆菌菌株细胞内的ROS水平升高。暴露于溶剂诱导下的BW25113∆katE∆katG和BW25113∆sodA∆sodB中的ROS水平高于BW25113中的ROS水平。这些结果表明，ROS清除酶有助于维持大肠杆菌对有机溶剂的耐受性。此外，暴露于正己烷会使sodA和sodB的启动子活性显著增加。
