Roles of the glutathione- and thioredoxin-dependent systems in the Escherichia coli responses to ciprofloxacin and ampic
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ORIGINAL PAPER
Roles of the glutathione‑ and thioredoxin‑dependent systems in the Escherichia coli responses to ciprofloxacin and ampicillin Galina Smirnova1 · Nadezda Muzyka1 · Elena Lepekhina1,2 · Oleg Oktyabrsky1,2
Received: 22 June 2015 / Revised: 13 January 2016 / Accepted: 23 May 2016 © Springer-Verlag Berlin Heidelberg 2016
Abstract Recently, it was proposed that some antibiotics stimulate the production of reactive oxygen species (ROS), which contribute to cell death. Later, other research groups have provided arguments against ROS-mediated killing of bacteria by antibiotics. At present, there remain a number of unanswered questions in understanding of the role of ROS in killing by antibiotics. Mutants of Escherichia coli in components of the thioredoxin and glutaredoxin redox pathways used in this study possess a great variability in antioxidant activity, and they therefore are a useful model for the investigation of the role of oxidative stress in bactericidal effect of antibiotics. Statistical analysis did not reveal a significant correlation between the susceptibility of the mutants to ciprofloxacin and ampicillin and their resistance to peroxide stress. However, we found strong reverse correlations between the bactericidal activity of antibiotics and the specific growth rate of these mutants at the moment of drug addition. Supplements changing the level of intraand extracellular glutathione considerably affected E. coli susceptibility to ciprofloxacin and ampicillin. The effect of
Communicated by Djamel Drider. Electronic supplementary material The online version of this article (doi:10.1007/s00203-016-1247-z) contains supplementary material, which is available to authorized users. * Oleg Oktyabrsky [email protected] 1
Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, Golev Street 13, Perm, Russia 614081
2
Department of Chemistry and Biotechnology, Perm National Research Polytechnic University, Komsomolsky pr., 29, Perm, Russia 614990
GSH precursors on bactericidal activity of antibiotics was also observed in gshA mutants. Keywords Escherichia coli · Antibiotics · Oxidative stress · Glutathione
Introduction It has been shown that under aerobic conditions bactericidal antibiotics with specific targets in bacterial cell stimulate the production of harmful reactive oxygen species (ROS), which contribute to killing by these drugs (Kohanski et al. 2007; Wang and Zhao 2009). Recently, oxidative stress theory was challenged by several research groups that have provided convincing arguments against ROS-mediated killing of bacteria by antibiotics (Keren et al. 2013; Liu and Imlay 2013). Oxidative stress is caused by exposure of cells to reactive oxygen species, such as superoxide anion (O·− 2 ), hydrogen peroxide (H2O2) and hydroxyl radical (HO·), which can damage DNA, proteins and cell membranes. In Escherichia coli, the main scavengers of O·− 2 are cytoplasmic superoxide dismutases MnSOD (sodA) and FeSOD (sodB) and periplasmic CuZnSOD (sodC) (Storz and Imlay 19
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