title: Toxicity of binary mixtures of metal oxide nanoparticles to Nitrosomonas europaea.
abstract: Although the widely used metal oxide nanoparticles (NPs) titanium dioxide NPs (n-TiO2), cerium dioxide NPs (n-CeO2), and zinc oxide NPs (n-ZnO) have been well known for their potential cytotoxicities to environmental organisms, their combined effects have seldom been investigated. In this study, the short-term binary effect of n-CeO2 and n-TiO2 or n-ZnO on a model ammonia oxidizing bacterium, Nitrosomonas europaea were evaluated based on the examinations of cells' physiological, metabolic, and transcriptional responses. The addition of n-TiO2 mitigated the negative effect of more toxic n-CeO2 and the binary toxicity (antagonistic toxicity) of n-TiO2 and n-CeO2 was generally lower than the single NPs induced one. While the n-CeO2/n-ZnO mixture exerted higher cytotoxicity (synergistic cytotoxicity) than that from single NPs. The increased addition of the less toxic n-CeO2 exaggerated the binary toxicity of n-CeO2/n-ZnO mixture although the solubility of n-ZnO was not significantly affected, which excluded the contribution of the dissolved Zn ions to the enhancement of the combined cytotoxicity. The cell membrane disturbances and NP internalizations were detected for all the NP impacted cultures and the electrostatic interactions among the two distinct NPs and the cells were expected to play a key role in mediating their direct contacts and the eventual binary nanotoxicity to the cells.
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, Nanjing, 210096, China. Electronic address: yuran@seu.edu.cn.
authors.forename: Ran
authors.initials: R
authors.lastname: Yu
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, Nanjing, 210096, China.
authors.forename: Junkang
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, Nanjing, 210096, China.
authors.forename: Meiting
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, Nanjing, 210096, China.
authors.forename: Guangcan
authors.initials: G
authors.lastname: Zhu
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, Nanjing, 210096, China.
authors.forename: Lianghui
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, Nanjing, 210096, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Civil and Environmental Engineering, University of Vermont, Burlington, VT, 05405, USA.
authors.forename: Huijie
authors.initials: H
authors.lastname: Lu
mesh_terms: D002462:Cell Membrane / Q000187:drug effects; D002563:Cerium / Q000633:toxicity*; D053768:Metal Nanoparticles / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D043370:Nitrosomonas europaea / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology; D014025:Titanium / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D012722:Sewage; C009495:titanium dioxide; D002563:Cerium; C030583:ceric oxide; D014025:Titanium; D015034:Zinc Oxide
keywords: Binary toxicity; Cell membrane; Electrostatic interaction; Nanoparticle; Nitrosomonas europaea