title: Role of oxidative stress in inactivation of Escherichia coli BW25113 by nanoscale zero-valent iron.
abstract: An Escherichia coli BW25113 wildtype strain and mutant strains lacking genes that protect against oxidative stress were examined at different growth phases for susceptibility to zero-valent iron (nZVI). Viability of cells was determined by the plate count method. All mutant strains were more susceptible than the wild type strain to nZVI; however, susceptibility differed among the mutant strains. Consistent with the role of rpoS as a global stress regulator, an rpoS gene knockout mutant exhibited the greatest susceptibility to nZVI under the majority of conditions tested (except exponential and declining phases at longer exposure time). Mutants lacking genes encoding the inducible and constitutively expressed cytosolic superoxide dismutases, sodA and sodB, respectively, were more susceptible to nZVI than a mutant lacking the gene encoding sodC, a periplasmic superoxide dismutase. This suggests that nZVI induces oxidative stress inside the cells via superoxide generation. Quantitative polymerase chain reaction was used to examine the expression of katG, a gene encoding the catalase-peroxidase enzyme, in nZVI-treated E. coli at different growth phases. Results showed that nZVI repressed the expression of katG in all but lag phases.
authors.affiliation: International Postgraduate Programs in Environmental Management, Graduate School Chulalongkorn University, Bangkok 10330, Thailand; Environmental and Conservation Sciences, North Dakota State University, Fargo, ND 58108, USA.
authors.forename: Krittanut
authors.initials: K
authors.lastname: Chaithawiwat
authors.affiliation: Department of Biochemistry, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Alisa
authors.initials: A
authors.lastname: Vangnai
authors.affiliation: Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, ND 58108, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: McEvoy
authors.affiliation: Department of Veterinary and Microbiological Sciences, North Dakota State University, Fargo, ND 58108, USA.
authors.forename: Birgit
authors.initials: B
authors.lastname: Pruess
authors.affiliation: Medora Corporation, Dickinson, ND 58601, USA.
authors.forename: Sita
authors.initials: S
authors.lastname: Krajangpan
authors.affiliation: Department of Civil and Environmental Engineering, North Dakota State University, Fargo, ND 58108, USA. Electronic address: eakalak.khan@ndsu.edu.
authors.forename: Eakalak
authors.initials: E
authors.lastname: Khan
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D007501:Iron / Q000494:pharmacology*; D053768:Metal Nanoparticles; D018384:Oxidative Stress
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D007501:Iron
keywords: Bacteria; Mutants; Nanoscale zero-valent iron; Stress genes; Toxicity