title: Short-term effects of TiO2, CeO2, and ZnO nanoparticles on metabolic activities and gene expression of Nitrosomonas europaea.
abstract: Nanosized TiO2 (n-TiO2), CeO2 (n-CeO2), and ZnO (n-ZnO) and bulk ZnO were chosen for a 4-h exposure study on a model ammonia oxidizing bacterium, Nitrosomonas europaea. n-ZnO displayed the most serious cytotoxicity while n-TiO2 was the least toxic one. The change of cell morphologies, the retardance of specific oxygen uptake rates and ammonia oxidation rates, and the depression of amoA gene expressions under NP stresses were generally observed when the cell densities and membrane integrities were not significantly impaired yet. The TEM imaging and the synchrotron X-ray fluorescence microscopy of the NPs impacted cells revealed the increase of the corresponding intracellular Ti, Ce or Zn contents and suggested the intracellular NP accumulation. The elevation of intracellular S contents accompanied with higher K contents implied the possible activation of thiol-containing glutathione and thioredoxin production for NP stress alleviation. The NP cytotoxicity was not always a function of NP concentration. The 200 mg L(-1) n-TiO2 or n-CeO2 impacted cells displayed the similar ammonia oxidation activities but higher amoA gene expression levels than the 20 mg L(-1) NPs impacted ones. Such phenomenon further indicated the possible establishment of an anti-toxicity mechanism in N. europaea at the genetic level to redeem the weakened AMO activities along with the NP aggregation effects.
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; Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, United States. Electronic address: yuran@seu.edu.cn.
authors.forename: Ran
authors.initials: R
authors.lastname: Yu
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, United States.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Fang
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, United States.
authors.forename: Ponisseril
authors.initials: P
authors.lastname: Somasundaran
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, United States. Electronic address: kc2288@columbia.edu.
authors.forename: Kartik
authors.initials: K
authors.lastname: Chandran
mesh_terms: D000641:Ammonia / Q000378:metabolism; D002563:Cerium / Q000633:toxicity*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005978:Glutathione / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000633:toxicity* / Q000648:ultrastructure; D043370:Nitrosomonas europaea / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010100:Oxygen / Q000378:metabolism; D017356:Synchrotrons; D013879:Thioredoxins / Q000378:metabolism; D014025:Titanium / Q000633:toxicity*; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: C009495:titanium dioxide; D002563:Cerium; D013879:Thioredoxins; C030583:ceric oxide; D000641:Ammonia; D014025:Titanium; D005978:Glutathione; D010100:Oxygen; D015034:Zinc Oxide
keywords: Ammonia oxidation; Nanoparticle; Nitrosomonas europaea; Synchrotron X-ray fluorescence microscopy; Toxicity