title: Atmospheric Nonthermal Plasma-Treated PBS Inactivates Escherichia coli by Oxidative DNA Damage.
abstract: We recently reported that phosphate-buffered saline (PBS) treated with nonthermal dielectric-barrier discharge plasma (plasma) acquires strong antimicrobial properties, but the mechanisms underlying bacterial inactivation were not known. The goal of this study is to understand the cellular responses of Escherichia coli and to investigate the properties of plasma-activated PBS. The plasma-activated PBS induces severe oxidative stress in E. coli cells and reactive-oxygen species scavengers, α-tocopherol and catalase, protect E. coli from cell death. Here we show that the response of E. coli to plasma-activated PBS is regulated by OxyR and SoxyRS regulons, and mediated predominantly through the expression of katG that deactivates plasma-generated oxidants. During compensation of E. coli in the absence of both katG and katE, sodA and sodB are significantly overexpressed in samples exposed to plasma-treated PBS. Microarray analysis found that up-regulation of genes involved in DNA repair, and E. coli expressing recA::lux fusion was extremely sensitive to the SOS response upon exposure to plasma-treated PBS. The cellular changes include rapid loss of E. coli membrane potential and membrane integrity, lipid peroxidation, accumulation of 8-hydroxy-deoxyguinosine (8OHdG), and severe oxidative DNA damage; reveal ultimate DNA disintegration, and cell death. Together, these data suggest that plasma-treated PBS contains hydrogen peroxide and superoxide like reactive species or/and their products which lead to oxidative changes to cell components, and are eventually responsible for cell death.
authors.affiliation: Center for Surgical Infections and Biofilms, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America; Drexel University School of Biomedical Engineering, Science and Health Systems, Philadelphia, Pennsylvania, United States of America.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Yost
authors.affiliation: Center for Surgical Infections and Biofilms, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America; Drexel University School of Biomedical Engineering, Science and Health Systems, Philadelphia, Pennsylvania, United States of America.
authors.forename: Suresh G
authors.initials: SG
authors.lastname: Joshi
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001272:Atmosphere / Q000737:chemistry*; D002021:Buffers; D002374:Catalase / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D019610:Cytoprotection / Q000187:drug effects; D004249:DNA Damage; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial; D050296:Microbial Viability / Q000187:drug effects*; D009154:Mutation; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D058626:Plasma Gases / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects; D013482:Superoxide Dismutase / Q000235:genetics
chemical_list: D000975:Antioxidants; D002021:Buffers; D058626:Plasma Gases; D017382:Reactive Oxygen Species; D002374:Catalase; D013482:Superoxide Dismutase