【摘要】 浮游细菌是水生生态系统的重要组成部分,是水体中氮素生物地球化学循环的主要驱动力.本研究于2016年5月采集丹江口库区库心和渠首2个生态位点表层水样,采用16S r DNA Miseq高通量测序技术研究其群落组成,发现其主要由变形菌门、放线菌门、拟杆菌门等12门、139属细菌组成,渠首样品浮游细菌群落多样性高于库心样品. PICRUSt功能预测分析表明,浮游细菌涉及氨基酸运输和代谢、转录、能量产生和转换等24个基因功能家族,表现出功能上的丰富性.其中35个参与氮代谢的KO(表示通路)中库心高于渠首为20个,渠首高于库心的为15个.两样品中检测到涉及固氮作用(nif H)、硝化作用(hao)、反硝化作用(nar G、nir K、nor B、nos Z)、氮同化还原及异化还原作用(nas A、nar B、nap A、nir A、nir B、nrf A)参与氮循环的关键基因相对丰度.综合基因功能家族预测基因拷贝数和氮循环相关基因丰度分析,丹江口库区库浮游细菌氮代谢能力整体趋势为库心高于渠首.本研究从细菌群落组成、功能角度初步分析了丹江口库区不同生态位点氮循环的差异,为丹江口水库水环境保护提供了参考依据.更多还原

【Abstract】 Bacterioplankton are important components of aquatic ecosystems,and play a crucial role in the global biogeochemical cycle of nitrogen. In this study,surface-water samples were collected from Kuxin( the center of Danjiangkou Reservoir) and Qushou( the Middle Route of the South-to-North Water Diversion Project’s canal head) in the Danjiangkou Reservoir in May 2016. Total DNA was isolated,and high-throughput sequencing was performed to analyze the community structure and diversity of bacteria. Phylogenetic analyses of 16 S r DNA sequences showed that bacterial communities included species from 12 major phylogenetic groups. The predominant phylogenetic groups included Proteobacteria, Bacteroidetes, Firmicutes, Cyanobacteria, and Verrucomicrobia. The microbial biodiversity of Danjiangkou Reservoir bacterioplankton was greater in water samples from Qushou than in those from Kuxin.PICRUSt( phylogenetic investigation of communities by reconstruction of unobserved states) was used to determine the metabolic and functional abilities of the observed bacterial communities. Our results revealed a wide genetic diversity of organisms involved in various essential processes,such as Amino acid transport and metabolism,Transcription,Energy production and conversion,and Carbohydrate transport and metabolism. Thirty-five metabolic pathways involving nitrogen were detected. Key genes impacting the nitrogen cycle were detected in both the Kuxin and Qushou samples,and these encoded enzymes involved in nitrogen fixation( nif H),nitrification( hao),denitrification( nar G、nir K、nor B、nos Z),and assimilatory and dissimilatory nitrogen reduction to ammonia( nas A、nar B、nap A、nir A、nir B、nrf A). Copy numbers of 16 S rRNA genes of each detected phylotype of Danjiangkou Reservoir bacterioplankton were uniformly higher in water samples from Kuxin than in water samples from Qushou. Our analyses of differences in nitrogen abatement potential between water samples,based on bacterial community composition and function,provide a foundation for setting water environmental protection policies in the Danjiangkou Reservoir.更多还原