长江干流浮游细菌群落结构及影响因素

为研究长江干流浮游细菌群落结构的空间分布规律及其环境影响因素，针对细菌16S rRNA基因，采用定量PCR和高通量测序技术，对2015年和2016年采集的长江干流自四川泸州到上海吴淞口共计40个样点进行分析。结果表明：水体中浮游细菌16S rRNA基因丰度为2.64×106~1.44×109 copies/L。上游（泸州至秭归）、中游（宜昌至湖口）和下游水体（湖口至上海入海口）的α多样性在3组间都没有呈现出显著差异性。长江干流浮游细菌在门水平上主要由变形菌门（Proteobacteria，7.49%~86.53%）、放线菌门（Actinobacteria，0.27%~54.72%）、厚壁菌门（Firmicutes，0.03%~90.95%）、拟杆菌门（Bacteroidetes，0.50%~45.36%）和异常球菌-栖热菌门（Deinococcus-Thermus，0.00%~23.96%）构成。在属或科水平上主要由丛毛单胞菌科（Comamonadaceae，0.03%~65.67%）、CL500-29_marine_group（0.00%~24.23%）、hgcI_clade（0.00%~28.82%）、芽孢杆菌属（Bacillus，0.00%~90.88%）和氢噬胞菌属（Hydrogenophaga，0.03%~38.55%）组成。从上中下游水体的浮游细菌群落组成来看，上游水体相对丰度最高的类群为Bacillus（0.00%~90.88%），中游和下游为Comamonadaceae（分别为0.60%~65.67%和2.87%~50.64%）。造成上中下游水体中浮游细菌群落组成差异的环境因子各不相同：影响上游的主要为pH和悬浮颗粒物（SS），影响中游的主要为溶解氧（DO），影响下游的主要为DO、水温（WT）和总磷（TP）。

Bacterioplankton Community Structure in the Mainstream of Yangtze River and Driving Factors

In order to study the community structure of bacterioplankton and the driving factors in the mainstream of Yangtze River, Quantitative Real-time PCR and high-throughtput sequencing targeting on the bacterial 16S rRNA gene were used. Water samples were collected from 40 sites from Luzhou (Sichuan province) to Wusongkou (Shanghai city) along the mainstream of Yangtze River. The results show that the 16S rRNA gene abundance of all sites range from 2.64×106 copies/L to 1.44×109 copies/L. There is no significant difference in α-diversity between upper (from Luzhou to Zigui), middle (from Yichang to Hukou) and lower (from Huayang to estuary) reaches. Meanwhile, the dominant phyla in the mainstream of Yangtze River are Proteobacteria (7.49%~86.53%), Actinobacteria (0.27%~54.72%), Firmicutes (0.03%~90.95%), Bacteroidetes (0.50%~45.36%) and Deinococcus-Thermus (0.00%~23.96%). The dominant taxa at genus or family level include Comamonadaceae (0.03%~65.67%), CL500-29_marine_group (0.00%~24.23%), hgcI_clade (0.00%~28.82%)、Bacillus (0.00%~90.88%) and Hydrogenophaga (0.03%~38.55%). Moreover, the taxa with the highest relative abundance in upper reaches is Bacillus (0.00~90.88%), while it is Comamonadaceae in middle and lower reaches (0.60%~65.67% and 0.03%~65.67%, respectively). Additionally, the driving factors of these differences of bacterioplankton community structure vary in three reaches. The key factors affected the community structure are pH and suspend solids (SS) in upper reaches, dissolved oxygen (DO) in middle reaches, and DO, water temperature (WT) and total phosphorus (TP) in lower reaches.