[Quantitative and qualitative analysis of total bacteria and ammonia-oxidizing bacteria in Buji River in wet season]

Microbial community structure and biomass in river water can reflect the situation of water quality in some extent. Nitrogen removal was mainly achieved by the nitrification and denitrification processes, and ammonia oxidation catalyzed by ammonia-oxidizing bacteria (AOB) is the first and rate-limiting step of nitrification. To explore the AOB community structure and biomass in nitrogen polluted river, water samples were collected from Buji River (Shenzhen) in wet season. Quantification of 16S rRNA copy numbers of total bacteria and AOB were performed by real-time PCR, and the microbial community structures were studied by denaturing gradient gel electrophoresis (DGGE). The results showed that the number of total bacterial 16S rRNA changed from 4.73 x 10(10) - 3.90 x 10(11) copies x L(-1) in the water samples. The copy numbers of AOB varied from 5.44 x 10(6) - 5.96 x 10(8)copies x L(-1). Redundancy discrimination analysis (RDA) showed that the main factors affecting the structure and the numbers of bacteria were different. For total bacteria, nitrate influenced the biomass significantly (P < 0.05) while nitrogen and heavy metals (Mn and Zn) were the main factors affecting the microbial community structures (P < 0.05). For AOB, ammonia and Zn were the main factors influencing the biomass while ammonia nitrogen and heavy metals (Mn and Zn) were the main factors affecting the microbial community structures. 16S rDNA sequences from the water samples indicated that the bacteria generally belonged to Epsilon-Proteobacteria, Gamma-Proteobacteria, Beta-Proteobacteria, and Delta-Proteobacteria. Nitrosomonas sp. and Nitrosospira sp. were the main AOB. Cluster analysis showed that water pollution in downstream resulted in evident difference in microbial community structure between upstream and downstream water samples.