title: Responses of a soil bacterium, Pseudomonas chlororaphis O6 to commercial metal oxide nanoparticles compared with responses to metal ions.
abstract: The toxicity of commercially-available CuO and ZnO nanoparticles (NPs) to pathogenic bacteria was compared for a beneficial rhizosphere isolate, Pseudomonas chlororaphis O6. The NPs aggregated, released ions to different extents under the conditions used for bacterial exposure, and associated with bacterial cell surface. Bacterial surface charge was neutralized by NPs, dependent on pH. The CuO NPs were more toxic than the ZnO NPs. The negative surface charge on colloids of extracellular polymeric substances (EPS) was reduced by Cu ions but not by CuO NPs; the EPS protected cells from CuO NPs-toxicity. CuO NPs-toxicity was eliminated by a Cu ion chelator, suggesting that ion release was involved. Neither NPs released alkaline phosphatase from the cells' periplasm, indicating minimal outer membrane damage. Accumulation of intracellular reactive oxygen species was correlated with CuO NPs lethality. Environmental deposition of NPs could create niches for ion release, with impacts on susceptible soil microbes.
authors.affiliation: Department of Biological Engineering, Utah State University, Logan, UT 84322, USA. cdimkpa@usu.edu
authors.forename: Christian O
authors.initials: CO
authors.lastname: Dimkpa
authors.forename: Alyssa
authors.initials: A
authors.lastname: Calder
authors.forename: David W
authors.initials: DW
authors.lastname: Britt
authors.forename: Joan E
authors.initials: JE
authors.lastname: McLean
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Anderson
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D003300:Copper / Q000633:toxicity*; D053768:Metal Nanoparticles / Q000737:chemistry*; D011549:Pseudomonas / Q000737:chemistry / Q000187:drug effects* / Q000201:enzymology; D012988:Soil Microbiology; D013499:Surface Properties; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D001426:Bacterial Proteins; D003300:Copper; D000469:Alkaline Phosphatase; D015034:Zinc Oxide; C030973:cupric oxide