Objective  To investigate the diversity of denitrifying bacteria in sediments of Guangzhou Liuxi River, and explore the effects of environmental factors on structure and abundance of bacterial community.

Method  The community structure and abundance of denitrifying bacteria in sediments were analyzed by constructing gene library and real-time quantitative PCR (RT-qPCR). The principal coordinate analysis (PCoA) and redundancy analysis (RDA) were used to investigate the correlations between denitrifying bacterial community and environmental factors.

Result  The composition and abundance of nirS-type denitrifier communities in different sampling sites of Liuxi River had distinctive discrepancy. Phylogenetic analysis showed that most of nirS gene sequences obtained in sediments had distant relationships with the known denitrifying bacteria, and the relationships with microorganisms from other environments were closer. The species that had close relationships with nirS-type denitrifier in sediments of Liuxi River were Rhodanobacter, Paracoccus, Polymorphum gilvum, Herbaspirillum and Thauera. Ammonium (NH₄⁺–N) and nitrate (NO₃^––N) contents had decisive effects on the structure of denitrifying bacterial community. ThenirS gene copy numbers were ranged from 8.26×10¹ to 5.45×10⁴ g^–1, and nirS-type denitrifier abundance was significantly correlated with chemical oxygen demand, total nitrogen, ammonium and nitrate concentrations.

Conclusion  The abundant occurrence of chemical contaminants and reactive nitrogen in Liuxi River significantly influences denitrifying bacterial community structure and diversity.