中文摘要：

利用16SrRNA基因测序分类学技术，分别以北京市区2011及2012年不同月份的降水样品中细菌的基因组DNA为模板，通过克隆、测序构建基因组文库，研究了北京市大气降水中细菌的群落结构组成及多样性变化．系统发育分析结果表明，变形菌门（Proteobacteria）（α-,β-，γ-）是北京市降水样品中细菌的优势菌群（75．6％～100％），另外包括拟杆菌门（Bacteroidetes）、放线菌fq（Actinobacteria）、异常球菌门fDeinococcus—Thermus）、蓝藻门（Cyanobacteria）、硝化螺菌门（Nitrospira）、厚壁菌门（Firmicutes）共7个主要门类的细菌，以及未定菌（TM7）．多样性指数分析结果显示，不同的降水样品，细菌群落结构组成及多样性均存在着差异性，冬季12月份雪水样品细菌群落结构多样性明显高千苴种垂节的样品细菌群落名样件（Shannon，H）特点县．冬季〉秋季〉夏季

英文摘要：

Atmosphere bioaerosols was always closely linked with the health of human beings and flora and fauna, however, recent studies suggested that the bio-aerosols may impact the environment and climate change directly by acting as cloud condensation nuclei （CCN） and/or ice nucleation （IN）. Unfortunately, there was still little knowledge about the composition of microbial community of the biological ice nucleis in the precipitation, especially, in China mainland. At present study, the precipitation samplers were taken from the Beijing city area. The sampling was carried out in different months in 2011 and 2012. The bacterial diversity was analyzed using the 16S rRNA gene sequencing based approaches. Seven clone libraries were established resulting from the different rain-water sampling months. The results indicated that Proteobacteria （75.6%-100%） were dominant in the precipitation including Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. While other bacterial communities such as Bacteroidetes, Actinobacteria, Deinococcus-Thermus, Cyanobacteria, Nitrospira and Firmicutes were involved as well. Furthermore, a small proportion of undetermined bacteria （TM7, 1.2%-7.2%） were also found. In addition, microbial diversity in the snow water samplers was obviously much more than that in the rain-water samplers, which suggested that some biological ice nuclei may present and influence in the formation of precipitation. Moreover, results showed that Pseudomonas, in which some strains with high effective ice nucleation activity, was also found in the samplers. Therefore, further concerns should be done for the climatic effect of these microbes.