Composition and predictive functional analysis of bacterial communities in surface sediments of the Danjiangkou Reservoir

湖泊沉积物微生物是水生态系统的重要组成部分，目前关于丹江口库区沉积物细菌群落和功能研究鲜见报道.于2017年5月对丹江口库区内5个典型生态点位表层沉积物进行采集，采用高通量测序技术对表层沉积物细菌群落组成进行研究，结果表明细菌群落主要由变形菌门（Proteobacteria）、绿弯菌门（Chloroflexi）、拟杆菌门（Bacteroidetes）、疣微菌门（Verrucomicrobia）和硝化螺旋菌门（Nitrospirae）等33个门和318个属组成，具有丰富的群落组成.沉积物细菌群落和理化指标冗余分析（RDA）结果表明，pH值、总磷、有机质和铵态氮含量均能显著影响沉积物细菌群落组成.细菌属分类单元与环境因子Spearman相关分析表明，变形菌门中11个属的细菌与环境因子显著相关，为与环境因子显著相关细菌的主要组成（占47.62%）.采用细菌群落功能预测软件PICRUSt（Phylogenetic Investigation of Communities by Reconstruction of Unobserved States）对表层沉积物细菌群落进行分析，结果表明沉积物细菌功能主要涉及能量产生和转换、信号转导机制、氨基酸运输和代谢、细胞壁/细胞膜/膜结构的生物合成等24个基因功能家族，表现出功能上的丰富性.基因功能家族预测基因拷贝数表现为台子山 > 宋岗 > 库心 > 渠首 > 黑鸡嘴.;Sediment microbial communities play crucial roles in biogeochemical cycles of aquatic systems, and knowledge of microbial community structure could improve our understanding of these roles. To the best of our knowledge, there is no study revealing the compositions and functions of bacterial communities in sediments of the Danjiangkou Reservoir so far. In this study, 5 surface sediment samples were collected from the reservoir in May 2017. High-throughput sequencing was performed to analyze the distribution characteristics of the community structure and diversity of bacteria, and their relationship with environmental factors. Phylogenetic analysis based on 16S rDNA sequences showed that bacterial communities could be divided into 33 major phylogenetic groups. The dominant phylogenetic groups included Proteobacteria, Chloroflexi, Bacteroidetes, Verrucomicrobia, Nitrospirae, Acidobacteria, Planctomycetes and Omnitrophica. The results of redundancy analysis (RDA) for the relationship between the 33 bacterial phyla and 7 environmental factors showed that the pH, total phosphorus, sediments organic matter, and ammonium nitrogen were the main environmental factors affecting the distribution characteristics of the bacterial community. Spearman correlation analysis was employed to explore associations between all bacterial genera and environmental factors; the genera significantly correlated with the environmental factors mainly belonged to the phylum Proteobacteria. PICRUSt was used to understand the metabolic and functional abilities of the observed bacterial communities. The results obtained showed wide genetic diversity of organisms involved in various essential processes, such as energy production and conversion, signal transduction mechanisms, amino acid transport and metabolism, cell wall/membrane/envelope biogenesis, translation, ribosomal structure and biogenesis, replication, recombination and repair. The surface sediments of the Danjiangkou Reservoir can be ranked in the following order based on the 16S rRNA gene copy number of the detected phylotype:Taizishan > Songgang > Kuxin> Qushou > Heijizui.