中文摘要：

为揭示三峡支流细菌群落的多样性和分布特征,采用高通量16s r DNA测序技术,于2014年5月对大宁河和香溪河细菌进行调查研究,同时检测水环境因子。结果表明,大宁河和香溪河细菌种类丰富,共检出细菌和古生菌25门,其中比例最高的为变形菌门,占69.01%,放线菌门其次,占11.46%。变形菌门中,γ-变形菌最多,占该门类总数的35.22%,β-变形菌其次,为22.18%。细菌多样性指数Shannon指数平均为13.2,Simpson指数接近于0,Chao1指数平均为48 633 611.4,可见三峡支流的细菌种类极其多样。几种丰度较高的细菌在空间上具有不同的分布特征。统计分析显示对细菌组成与分布影响最显著的因子为总无机碳,其次是总有机碳、叶绿素,其它因子影响较小。放线菌、γ-变形菌、δ-变形菌和浮霉菌与总有机碳正相关。叶绿体纲细菌和叶绿素含量存在正相关,而变形菌、梭菌纲细菌则与其负相关。变形菌与氮磷和总碳成较强的正相关,所以碳源的增加使变形菌丰度提高。营养水平是影响细菌群落结构的重要因素之一。营养水平越高,α-变形菌比例越高。营养水平低则δ-变形菌比例上升。支流上不同河段的环境因子有明显的空间分布的差异（P〈0.05）。这些差异造成了大宁河和香溪河细菌群落结构的空间异质性。

英文摘要：

Investigation was carried out in Daning River and Xiangxi River,two tributaries of Three Gorges reservoir,in May 2014 by the use of high-throughput sequencing technology 16 s r DNA in a bid to discover the diversity and distribution of the bacterial communities in those revers;at the same time water quality parameters were detected there.The investigation showed that the tributaries were very much prolific in bacteria species：a total of 25 phyla of bacteria and archaea were detected,among others,Proteobacteria accounting for 69.01%,the highest in proportion,which was followed by Actinobacteria,accounting for 11.46%.As to the Proteobacteria,the γ-Proteobacteria was the most prolific,accounting for35.22%,and the β-Proteobacteria was the second,22.18%.The Shannon index averaged 13.2,the Simpson index was close to zero,and the average Chao1 index 48 633 611.4,which suggested that there were abundant bacteria species in the tributaries of Three Gorges reservoir,and several bacteria of high abundance were different in the spatial distribution.The most significant environmental factors affecting the composition and distribution of bacteria was total inorganic carbon,followed by total organic carbon and chlorophyll a;however,other factors affected less.Actinobacteria,γ-Proteobacteria,δ-Proteobacteria and Planctomycetes were closely related to total organic carbon;Chloronema and chlorophyll content was positively correlated,while Proteobacteria and Clostridia were negatively correlated with it.In addition,Proteobacteria were in rather strongly positive correlation with nitrogen,phosphorus and total carbon,respectively,the increase of carbon source would lead to the abundance increase of Proteobacteria.Summarily,nutrition was one of the important factors that affectedthe bacterial community structure：the higher trophic level,the higher α-Proteobacteria proportion would be;when trophic level reduced,the δ-Proteobacteria rose.On the other hand,environmental factors varied in different reaches of the tributaries had