title: Toxicity of TiO₂ nanoparticle to denitrifying strain CFY1 and the impact on microbial community structures in activated sludge.
abstract: The antibacterial activity of titanium dioxide nanoparticles (TiO2 NPs) is well described, but little is known of their impact on specific microbial functions such as denitrification, nor on microbial community structure. In this study, a denitrifier (named as Pseudomonas stutzeri CFY1), which was isolated from the activated sludge and could remove up to 111.68 mg/L of NO3(-)-N under aerobic conditions, was utilized to evaluate the influences of TiO2 NPs on its nitrogen removal ability and associated gene expression under aerobic conditions. The variations of the bacterial diversity of activated sludge were also observed. The results showed that antibacterial activity increased with increasing concentrations of TiO2 NPs. Increased production of reactive oxygen species was responsible for TiO2 NPs toxicity. An up-regulation of denitrification genes was observed with increasing concentrations of TiO2 NPs under aerobic conditions. Accordingly, denitrification by P. stutzeri was accelerated when the concentration of TiO2 NPs was increased to 50 mg/L. However, the denitrification of CFY1 was inhibited at low concentrations of TiO2 NPs (5-25 mg/L), indicating that assimilatory and dissimilatory denitrification were synchronized in P. stutzeri CFY1; the latter process plays a major role in denitrification. Further study of the community using 454 pyrosequencing showed that after 7 days of exposure to 50 mg/L TiO2 NPs, the microbial composition of the activated sludge was significantly different and had a lower diversity compared to the controls.
authors.affiliation: College of Resources and Environment, Northeast Agricultural University, Harbin 150030, China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Radiology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.affiliation: College of Resources and Environment, Northeast Agricultural University, Harbin 150030, China.
authors.forename: Qiaoruo
authors.initials: Q
authors.lastname: Wang
authors.affiliation: College of Resources and Environment, Northeast Agricultural University, Harbin 150030, China. Electronic address: houning571@163.com.
authors.forename: Ning
authors.initials: N
authors.lastname: Hou
authors.affiliation: College of Resources and Environment, Northeast Agricultural University, Harbin 150030, China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Li
authors.affiliation: College of First Clinical Medicine, Harbin Medical University, Harbin 150001, China.
authors.forename: Xiaosong
authors.initials: X
authors.lastname: Cheng
mesh_terms: D000332:Aerobiosis; D058440:Denitrification; D004305:Dose-Response Relationship, Drug; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D009584:Nitrogen / Q000378:metabolism; D044223:Pseudomonas stutzeri / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D014025:Titanium / Q000737:chemistry / Q000633:toxicity*; D015854:Up-Regulation
chemical_list: D017382:Reactive Oxygen Species; D012722:Sewage; C009495:titanium dioxide; D014025:Titanium; D009584:Nitrogen
keywords: Activated sludge; Microbial community; Pseudomonas stutzeri; TiO(2) nanoparticle; Toxicity