河流中微生物的数量和群落结构能在一定程度上反映水环境状况.氨氧化细菌驱动的硝化作用是氮素转化的主要机制,为了解氮素污染河流中氨氧化细菌的群落组成及数量,采用变性梯度凝胶电泳(denaturing gradient gel electrophoresis,DGGE)和Real-time PCR技术分析了布吉河丰水期不同断面水样中总细菌和氨氧化细菌的群落结构以及数量变化.结果表明,水样中总细菌(16S rRNA)和氨氧化细菌(16S rRNA)数量变化范围分别为4.73×1010~3.90×1011copies.L-1和5.44×106~5.96×108copies.L-1.冗余度分析表明影响微生物数量和群落结构的水环境因子不同:对于总细菌,与其数量显著相关的环境因子是硝氮(P〈0.05),与其群落结构显著相关的环境因子是氮素(三氮)和金属(Mn和Zn)(P〈0.05);对于氨氧化细菌(ammonia-oxidizing bacteria,AOB),与其数量显著相关的是氨氮和Zn(P〈0.05),与其群落组成显著相关的是氨氮、Mn和Zn(P〈0.05).测序结果表明在布吉河水样中微生物属于变形菌门(Proteobacterium)的Epsilon-Proteobacteria、Gamma-Proteobacteria、Beta-Proteobacteria和Delta-Proteobacteria这4个纲,氨氧化细菌与Nitrosomonas sp.和Nitrosospira sp.属的细菌相似度较高,且Nitrosospira sp.为优势菌属.由于污染影响,布吉河上游和下游微生物群落结构明显不同.
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 4.73×1010-3.90×1011copies·L-1 in the water samples.The copy numbers of AOB varied from 5.44×106-5.96×108 copies·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.