title: Physiological and transcriptional responses of Nitrosomonas europaea to TiO2 and ZnO nanoparticles and their mixtures.
abstract: The short-term combined effects of two most extensively used nanoparticles (NPs) TiO2 NPs (n-TiO2) and ZnO NPs (n-ZnO) versus their individual cytotoxicities on a model ammonia-oxidizing bacterium, Nitrosomonas europaea, were investigated at both physiological and transcriptional levels. n-ZnO exerted more serious impairment effects on cell morphology, cell density, membrane integrity, and ammonia monooxygenase activity than n-TiO2. However, the co-existing n-TiO2 displayed a dose-dependent mitigation effect on n-ZnO cytotoxicity. Consistently, the n-TiO2 and n-ZnO mixture-impacted global transcriptional expression profile, obtained with the whole-genome microarray technique, was more comparable to the n-TiO2-impacted one than that impacted by n-ZnO. The expressions of numerous genes associated with heavy metal scavenging, DNA repair, and oxidative stress response were less up-regulated under the binary impacts of NP mixture than n-ZnO. Moreover, only n-ZnO alone stimulated the up-regulations of heavy metal resistance genes, which further implied the capacity of co-existing n-TiO2 to alleviate n-ZnO cytotoxicity. In addition, the damage of cell membrane structures and the suppression of cell membrane biogenesis-related gene expressions under the influence of either individual NPs or their combinations strongly suggested that the interruption of cell membranes and the associated metabolic activities would probably be one of NPs' critical cytotoxicity mechanisms.
authors.affiliation: Department of Environmental Science and Engineering, School of Energy and Environment, Wuxi Engineering Research Center of Taihu Lake Water Environment, Southeast University, No. 2 Sipailou Street, Nanjing, 210096, China. 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, No. 2 Sipailou Street, 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, No. 2 Sipailou Street, 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, No. 2 Sipailou Street, 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, No. 2 Sipailou Street, Nanjing, 210096, China.
authors.forename: Guangcan
authors.initials: G
authors.lastname: Zhu
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: D053768:Metal Nanoparticles / Q000008:administration & dosage*; D043370:Nitrosomonas europaea / Q000187:drug effects* / Q000235:genetics; D010084:Oxidation-Reduction; D014025:Titanium / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*; D015034:Zinc Oxide / Q000494:pharmacology*
chemical_list: C009495:titanium dioxide; D014025:Titanium; D015034:Zinc Oxide
keywords: Combined effect; Microarray; Nanoparticle; Nitrosomonas europaea; Toxicity; Transcriptional response