title: Ag nanoparticles generated using bio-reduction and -coating cause microbial killing without cell lysis.
abstract: Cost-effective "green" methods of producing Ag nanoparticles (NPs) are being examined because of the potential of these NPs as antimicrobials. Ag NPs were generated from Ag ions using extracellular metabolites from a soil-borne Pythium species. The NPs were variable in size, but had one dimension less than 50 nm and were biocoated; aggregation and coating changed with acetone precipitation. They had dose-dependent lethal effects on a soil pseudomonad, Pseudomonas chlororaphis O6, and were about 30-fold more effective than Ag(+) ions. A role of reactive oxygen species in cell death was demonstrated by use of fluorescent dyes responsive to superoxide anion and peroxide accumulation. Also mutants of the pseudomonad, defective in enzymes that protect against oxidative stress, were more sensitive than the wild type strain; mutant sensitivity differed between exposure to Ag NPs and Ag(+) ions demonstrating a nano-effect. Imaging of bacterial cells treated with the biocoated Ag NPs revealed no cell lysis, but there were changes in surface properties and cell height. These findings support that biocoating the NPs results in limited Ag release and yet they retained potent antimicrobial activity.
authors.affiliation: Department of Biology, Utah State University, Logan, UT, 84322-5305, USA.
authors.forename: Aniket
authors.initials: A
authors.lastname: Gade
authors.affiliation: Department of Biological Engineering, Utah State University, Logan, UT, 84322, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Adams
authors.affiliation: Department of Biological Engineering, Utah State University, Logan, UT, 84322, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Britt
authors.affiliation: Science Engineering Research (SER) 005. UMC 4415, Utah State University, Logan, UT, 84322, USA.
authors.forename: Fen-Ann
authors.initials: FA
authors.lastname: Shen
authors.affiliation: Utah Water Research Laboratory, Utah State University, Logan, UT, 84322, USA.
authors.forename: Joan E
authors.initials: JE
authors.lastname: McLean
authors.affiliation: Department of Plants Soils and Climate, Utah State University, Logan, UT, 84322, USA.
authors.forename: Astrid
authors.initials: A
authors.lastname: Jacobson
authors.affiliation: Institute of Environmentally-Friendly Agriculture, Chonnam National University, Gwangju, 500-757, Korea.
authors.forename: Young-Cheol
authors.initials: YC
authors.lastname: Kim
authors.affiliation: Department of Biology, Utah State University, Logan, UT, 84322-5305, USA. anne.anderson@usu.edu.
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Anderson
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D019149:Bioreactors; D006861:Hydrogen Peroxide / Q000494:pharmacology; D053768:Metal Nanoparticles / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D010316:Particle Size; D000070096:Pseudomonas chlororaphis / Q000187:drug effects / Q000648:ultrastructure; D011775:Pythium / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000890:Anti-Infective Agents; D017382:Reactive Oxygen Species; D012834:Silver; D006861:Hydrogen Peroxide
keywords: Ag; Antimicrobial; Biocoating; Green synthesis; Oxidative stress