title: Silver-ion-mediated reactive oxygen species generation affecting bactericidal activity.
abstract: Silver ions have been widely used as disinfectants that inhibit bacterial growth by inhibiting the essential enzymatic functions of the microorganism via interaction with the thiol-group of l-cysteine. However, silver-ion-mediated perturbation of the bacterial respiratory chain has raised the possibility of reactive oxygen species (ROS) generation. We used bacterial reporter strains specifically responding to superoxide radicals and found that silver-ion-mediated ROS-generation affected bactericidal activity. Almost half the log reduction in Escherichia coli and Staphylococcus aureus populations (model strains for gram negative and positive bacteria, respectively) caused by silver-ion disinfection was attributed to ROS-mediated bactericidal activity. The major form of ROS generated was the superoxide-radical; H(2)O(2) was not induced. Furthermore, silver ions strongly enhanced paraquat-induced oxidative stress, indicating close correlation and synergism between the conventional and ROS-mediated silver toxicity. Our results suggest that further studies in silver-based disinfection systems should consider the oxygen concentration and ROS reaction.
authors.affiliation: School of Chemical and Biological Engineering, College of Engineering, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Hee-Jin
authors.initials: HJ
authors.lastname: Park
authors.forename: Jee Yeon
authors.initials: JY
authors.lastname: Kim
authors.forename: Jaeeun
authors.initials: J
authors.lastname: Kim
authors.forename: Joon-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Ji-Sook
authors.initials: JS
authors.lastname: Hahn
authors.forename: Man Bock
authors.initials: MB
authors.lastname: Gu
authors.forename: Jeyong
authors.initials: J
authors.lastname: Yoon
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000633:toxicity; D004926:Escherichia coli / Q000187:drug effects*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009566:Nitrates / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D010269:Paraquat / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D012834:Silver / Q000737:chemistry* / Q000494:pharmacology* / Q000633:toxicity; D012835:Silver Nitrate / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D009566:Nitrates; D017382:Reactive Oxygen Species; D012834:Silver; C031618:sodium nitrate; D012835:Silver Nitrate; D006861:Hydrogen Peroxide; D010269:Paraquat