中文摘要：

【目的】揭示乌梁素海浮游细菌的群落结构及其对富营养化环境因子的响应，认识乌梁素海浮游细菌多样性，以丰富微生物与富营养化关系的理论。【方法】提取水体浮游细菌总DNA，利用细菌通用引物对63F／1387R进行PCR扩增，构建小口、沙尖北和红圪卜3个湖区16SrRNA基因克隆文库；以典型对应分析（CCA）方法解析浮游细菌群落结构对环境因子的响应。【结果】各湖区中富营养化程度最重的红圪卜位点细菌多样性、丰富度及均匀度最高，而富营养化程度最轻的小口位点细菌多样性、丰富度及均匀度最低。Proteobacteria、Bacteroidetes和Actinobacteria为水体中优势类群。α-、γ-，σ-Proteobacteria，Actinobacteria及Bacteroidetes等菌群丰度随着水体的富营养化程度改变而有显著的变化。各湖区皆存在许多可能具有污染物降解及驱动生源要素循环能力的细菌类群。CCA分析表明TN、NH4＋、N03-和c0D等水体指标对浮游细菌群落结构组成的影响较大。此外，乌梁素海水体内未知细菌类群很多；且不同于一般淡水生态系统，乌梁素海中存在9．6％的轻度嗜盐碱性细菌。【结论】乌梁素海水体中浮游细菌多样性较高，细菌群落结构复杂、其类群组成与富营养化因子紧密相关。

英文摘要：

[Objective] To investigate the planktonic bacterial community structure in Lake ULanSuHai and reveal its response to eutrophic factors. [Methods] DNA of total planktonic bacteriawas extracted and used as template in the PCR amplification with bacterial universal primer pair 63F/1387R, and then PCR products were subjected to constructing 16S rRNA gene clone libraries of 3 different eutrophication level lake area, XK, HGB and SJB. Canonical correlation analysis （CCA）assay was applied to reveal the responses or-bacterial community to eutrophication, lResultsl The highest eutrophication level lake area-HGB has the highest diversity, richness and evenness, whereas XK of lowest eutrophication has the lowest diversity indexes. Proteobacteria, bacteroidetes andactinobacteria were dominant bacterial groups in Lake ULanSuHai. Abundances of α-, γ-, σ- proteobacteria, actinobacteria and bacteroidetes were varied greatly with the shifts of eutrophic levels. A lot of functional microbes with the probable ability degrading pollutants and cycling biogenicelements were detected in all sampled lake areas. Moreover, CCA analysis suggested that TN, NH4＋, NO3- and COD had the most influence on planktonic bacterial community composition. Besides, there were plenty of unknown groups in Lake ULanSuHai. Some slightly alkaphilic and halotolerent bacteriawere detected and they accounted for 9.6% of total bacteria in Lake ULanSuHai. [Conclusion] The diversity of planktonic bacteria is high in Lake ULanSuHai, and the community structure is complex and its composition is closely correlated with the eutrophic level of the lake waterbody.