Physiological and transcriptional responses of nitrifying bacteria exposed to copper in activated sludge.
Cu inhibition of gene transcription in ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were rarely studied simultaneously in activated sludge. In this study, the transcription of amoA (for AOB) and nxrB (for NOB), nitrification efficiencies, AOB and NOB respiratory rates, and Cu distribution were simultaneously investigated. Modeling the relationships among the aforementioned parameters revealed that in complex activated sludge systems, nitrification efficiency was an insensitive parameter for showing Cu inhibition. Respiration activities and gene transcription were sensitive to Cu and positively correlated with each other. The transcription of amoA and nxrB genes indicated that the Cu had different inhibitory effects on AOB and NOB. AOB were more susceptible to Cu toxicity than NOB. Moreover, the degree of Cu inhibition on ammonia oxidation was greater than on nitrite oxidation. The analysis and related modeling results indicate that the inhibitory actions of Cu on nitrifying bacteria could mainly be attributed to intracellular Cu. The findings from this study provide insight into the mechanism of Cu inhibition on nitrification in complex activated sludge systems.
School of Environmental Science and Engineering, Tianjin University, Weijin Road 92, Tianjin 300072, China.
Fan
F
Ouyang
School of Environmental Science and Engineering, Tianjin University, Weijin Road 92, Tianjin 300072, China. Electronic address: zhaihy@tju.edu.cn.
Hongyan
H
Zhai
School of Environmental Science and Engineering, Tianjin University, Weijin Road 92, Tianjin 300072, China.
Min
M
Ji
School of Environmental Science and Engineering, Tianjin University, Weijin Road 92, Tianjin 300072, China; Anhui Urban & Rural Planning and Design Institute, South Tongcheng Road 363, Hefei 230022, Anhui, China.
Hongyang
H
Zhang
Harvard T. H. Chan School of Public Health, Department of Environmental Health, 401 Park Drive, Landmark Center West 415, Boston, MA 02215, USA.
Zhao
Z
Dong
D001419:Bacteria / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors; D003300:Copper / Q000032:analysis / Q000633:toxicity*; D005798:Genes, Bacterial; D058465:Nitrification; D010100:Oxygen / Q000378:metabolism; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D014158:Transcription, Genetic; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
D012722:Sewage; D014874:Water Pollutants, Chemical; D003300:Copper; D010100:Oxygen
Activated sludge; Copper distribution; Nitrification inhibition; mRNA; sOUR