Role of the ArcAB two-component system in the resistance of Escherichia coli to reactive oxygen stress

To investigate the mechanism of ROS resistance mediated by ArcAB, we generated deletion mutants of ArcA and ArcB in E. coli. Our results demonstrated that both ArcA and ArcB were necessary for resistance to hydrogen peroxide (H2O2), a type of ROS, and their function in this resistance was independent from H2O2 scavenge. Mutagenesis analysis of ArcA indicated that ROS resistance was mediated through a distinct signaling pathway from that used in anaerobic conditions. An abundant protein flagellin was elevated at both the protein and mRNA levels in the ΔarcA mutant as compared to the wild type E. coli, and deletion of flagellin restored the resistance of the ΔarcA mutant to H2O2. The resistance of the ΔarcA mutant E. coli to H2O2 can also be restored by amino acid supplementation, suggesting that a deficiency in amino acid and/or protein synthesis in the mutant contributed to its susceptibility to H2O2, which is consistent with the notion that protein synthesis is necessary for ROS resistance.Our results suggest that in addition to its role as a global regulator for anaerobic growth of bacteria, ArcAB system is also important for bacterial resistance to ROS in aerobic conditions, possibly through its influence on bacterial metabolism, especially amino acid and/or protein assimilation and synthesis.Aerobic bacteria use oxygen as a terminal electron acceptor in oxygen-containing environments for their metabolism. Although aerobic growth has its obvious advantages (e. g. high energy efficiency, abundance of oxygen in the atmosphere, etc), bacteria must deal with the undesired consequences from exposure to oxygen and oxidative environments. Oxygen and its derivatives, such as superoxide and hydrogen peroxide, are often highly reactive and pose a threat to many macromolecules, such as enzymes with iron-sulfur centers, nucleic acids, and lipids. Therefore, bacteria undergoing aerobic growth must be able to sense, respond to, and detoxify reactive oxygen species (ROS), and m