不同海拔湖泊沉积物中细菌及真核微生物群落及功能多样性的分布格局及构建机制

Microorganisms are one of the most important components of the lake ecosystems. The elevational patterns of diversity for macroorganisms, such as plants and animals, have been well documented. In contrast, the elevational distribution of microbial communities has received less examination. To the best of our knowledge, almost no studies have investigated the elevational patterns of the composition and function of bacterial and microeukaryotic communities in lake sediments. In this proposed study, we focus on the bacterial and microeukaryotic communities in lake sediments at different elevations. The following studies will be conducted. Field investigations will be firstly performed. Sediment samples from different elevational lakes will be collected and molecular techniques, including Illumina pyrosequencing and Geochip, will be carried out to investigate the elevational patterns of the composition and function of bacterial and microeukaryotic communities in lake sediments. The in situ microcosms will be subsequently constructed within representative lakes at different elevations. The sediment columns of the microcosms will be transplanted among different elevational lakes. The composition and function of bacterial and microeukaryotic community will be examined to investigate their responses to the varied elevational and climatic environments. Then, microcosms will be constructed in laboratory to examine the effects of the variation of single environmental factor on the composition of bacterial and microeukaryotic communities in the sediments of different elevational lakes. After that, the datasets of climatic conditions, sediment properties, and the composition and function of bacterial and microeukaryotic communities will be combined. Multivariate statistical analysis and network analysis will be carried out with these datasets. Based on the above analyses, the influences of elevation on the composition and function of the microbial communities will be elucidated, and the elevational patterns and assembly mechanisms of the microbial communities will be revealed at last. The obtained results would provide further insights for understanding the basic theory of microbial ecology in the lake ecosystem.

微生物是湖泊生态系统的重要组成部分。相比于大型动、植物，人们对微生物群落海拔梯度格局的了解还非常少，更加缺乏对湖泊沉积物中微生物群落组成和功能沿海拔梯度变化规律的认知。本研究拟以不同海拔高度湖泊沉积物中细菌和真核微生物群落为研究对象，开展如下研究。进行野外观测，采集不同海拔湖泊沉积物样品，应用高通量测序、基因芯片等技术，获取微生物群落组成和功能多样性沿海拔梯度的变化特征；选取不同海拔典型湖泊，构建野外模拟系统，将模拟系统在不同海拔间移植，探索微生物群落组成和功能对气候环境改变的响应；室内构建微宇宙，探讨单一因子变化对不同海拔湖泊沉积物中微生物群落的影响。将海拔气候特征、微生物群落组成与功能、沉积物理化因子三者结合，应用多元统计、网络分析等方法，阐明海拔变化对微生物群落组成及功能的影响，揭示湖泊沉积物中微生物群落多样性海拔梯度格局及其构建机制。预期成果将丰富对湖泊微生物生态学基础理论的认识。

微生物是湖泊生态系统的重要组成部分。相比于大型动、植物，人们对微生物群落海拔梯度格局的了解还非常少，更加缺乏对湖泊沉积物中微生物群落组成和功能沿海拔梯度变化规律的认知。本课题以我国四川省阿坝藏族羌族自治州四姑娘山不同海拔湖泊为研究对象，采集该区域内多个湖泊的沉积物样品，应用高通量测序技术对沉积物样品中总细菌和真核微生物群落的多样性和组成进行研究。同时，应用基因芯片（Geochip 5.0）技术对包括碳、氮、磷、硫和应激反应等在内的393个功能基因家族的14.4万个基因的信号强度进行检测，探索沉积物中微生物功能基因组成和多样性沿海拔梯度的变化规律。结果显示：沉积物中细菌群落的α多样性均随海拔升高呈现显著的单调下降格局；真核微生物群落的α多样性随海拔升高呈现波动变化的趋势；微生物功能基因类群α多样性及各种基因类群的代谢潜力在低海拔湖泊沉积物中最低，在高海拔湖泊沉积物中较高。此外，同一海拔湖泊沉积物中的细菌、真核微生物群落以及微生物功能基因组成更为相似，这说明沉积物中的微生物群落和功能基因组成具有明显的海拔格局。典范对应分析（CCA）、Mantel检验以及相关性分析表明：pH、总氮、硝氮、亚硝氮、氨氮、总磷、温度和海拔等因子对细菌和真核微生物群落结构有较大的影响，而微生物功能基因组成主要受海拔影响。群落构建分析结果表明：确定性过程在细菌群落构建过程中的作用随着海拔升高而增强，环境过滤是影响不同海拔沉积物中细菌群落构建的主要因素，并且这种影响在高海拔地区更为明显。不同海拔沉积物中微生物功能基因互作网络分析进一步表明：海拔是介导不同湖泊沉积物中微生物功能基因互作网络的最重要的因子。本研究揭示了湖泊沉积物中微生物群落多样性海拔梯度格局及其构建机制，阐明了湖泊表层沉积物中细菌和真核微生物群落沿海拔梯度的分布特征，有助于丰富对湖泊微生物生态学基础理论的认识。