Abstract

Diversity of nitrous oxide reductase genes (NosZ) in activated sludge was compared in the biological treatment process (BTCs, anaerobic, anoxic and aerobic process) of three municipal wastewater treatment plants located in different geographic regions. A total of 18 specific bands generated after polymerase chain reaction- denaturing gradient gel electrophoresis (PCR-DGGE) analysis. The diversity of NosZ in MWTPs of Nanjing is higher than that of Xiamen and Foushan, and the similarity of DGGE bands from BTCs in the same MWTP is obviously higher than that of the same BTC in different MWTPs. 12 of 18 unique bands were selected, sequenced and identified by searching against Genbank using BLASTn, and the highest identity and score values of the isolated sequences were the NosZ gene of uncultured bacterium in non-redundant database of Genbank. However, the most probable affiliations of the bacteria harboring the NosZ gene were the denitrifying bacteria from α- or β-proteobacteria, including Alicycliphilus denitricans, Herbaspirillum sp., Paracoccus denitrificans, and Rhodopseudomonas palustris. Phylogenetic analysis of the twelve sequences indicated that all the sequences could be divided into two main clusters. Each cluster not only contains species from α- proteobacteria but also from β-proteobacteria.

Key words: Denaturing gradient gel electrophoresis (DGGE), municipal wastewater treatment plants, nitrous oxide reductase, diversity