湖滨带芦苇根际细菌群落的环境响应及构建机制

Plant roots harbour abundant and diverse bacterial microbiota, and rhizosphere is considered as one of the most complicated ecosystems on Earth. Compared with the bacterial community in the rhizosphere of terrestrial plants, we know only little about the rhizosphere microbes associated with the aquatic plants. Knowledge about the effects of soil properties, climatic and environmental factors, plant growth period on the microbial communities in the rhizosphere of aquatic plants is also lacking. In this study, we focus on the bacterial community in the rhizosphere of Phragmites australis in the aquatic-terrestrial ecotone of the plain and plateau to carry out the following research. Firstly, rhizosphere samples of Phragmites australis in the lakeshore zone of plain and plateau will be collected in summer and winter for the field investigation. The diversity, composition and activity of the bacteria community will be examined with the high-throughput sequencing. Then, the control experiments will be carried out in greenhouse to explore how these variables (soil properties, climatic and environmental factors, plant genotype and growth periods) affect the bacterial community in the rhizosphere of Phragmites australis. The data of the above mentioned variables combined with the data of bacterial community will be analyzed by multivariate statistics, network analysis and phylogenetic structure analysis to clarify the influences of these factors on the bacterial community in the rhizosphere of Phragmites australis. The assembly mechanisms and associated influencing factors of the bacterial community in the rhizosphere samples could be revealed by the community assembly theories based on processes. The obtained results will be helpful for better understand the basic theory of microbial ecology in the rhizosphere of aquatic plants.

植物根际所含微生物类群众多，被认为是地球上最复杂的生态系统之一。当前，相比于陆生植物，人们对湖泊水生植物根际微生物群落的了解还非常少，更加缺乏对土质、气候环境、植株基因型及生长阶段等因素调控水生植物根际微生物群落规律的认知。本研究以平原和高原湖滨带芦苇根际细菌群落为研究对象，开展如下研究：首先，进行野外观测，在夏季和冬季分别采集平原和高原湖滨带芦苇根际样品，应用高通量测序技术获取根际细菌群落多样性、组成及活性数据；然后，构建温室控制试验，探讨土质、气候环境、植株基因型、生长阶段等因素对芦苇根际细菌群落的影响。将上述因素数据与根际细菌群落多样性、组成及活性数据相结合，应用多元统计、网络分析、细菌群落系统发育结构分析等方法，阐明上述因素对芦苇根际细菌群落的影响。结合基于过程的细菌群落构建理论，揭示芦苇根际细菌群落的构建机制及其影响因素。预期成果将丰富对水生植物根际微生物生态学基础理论的认识。

根际细菌群落是陆地和水生生态系统中养分循环过程的重要驱动者。相比于陆生植物，目前人们对水生植物根际微生物群落组成及其构建机制还缺乏了解，也不清楚多种因素（如：土壤理化性质、水位条件、植物的基因型、生长阶段等）单一或联合作用时会对植物及其根际微生物群落的多样性、组成、活性和构建机制产生何种影响。本研究选取湖泊湖滨带广泛分布的挺水植物芦苇作为研究对象，采用以高通量测序为主的分子生物学技术方法以及以多元统计分析为主的生物信息学分析方法，开展研究。结果表明：（1）本研究得到的芦苇样品中长江中下游芦苇居群基因水平上的变异程度较云贵高原的低。芦苇居群的亲缘关系和地理距离成负相关；（2）与活性菌群相比，常驻菌群具有显著较高的alpha多样性和较低的beta多样性；夏季根际细菌群落中潜在活性类群的比例较低；生态位分化和季节变化对芦苇根际常驻和活性细菌群落的构建起着重要的驱动作用，而水位因素对细菌群落的影响较弱。（3）对比了夏季和冬季芦苇非根际沉积物以及与根相关的隔室（即根际和内生）中的细菌群落组成及其群落构建过程发现：在这两个季节，根际细菌群落的alpha多样性最高，beta多样性最低；与冬季相比，夏季三个隔室的alpha多样性和beta多样性显著增加；在这两个季节，根际沉积物是根内生细菌的主要来源（约70%）。随机性过程主要影响根内生细菌群落组成，而确定性过程和随机性过程都决定根际细菌群落组成；随机性过程与确定性过程的相对重要性取决于季节。本研究选取在世界范围内均广泛分布的挺水植物芦苇作为研究对象，将野外观测与控制试验研究相结合，探索芦苇根际细菌群落的时空异质性及其构建机制，研究结果有助于深化对水生植物根际微生物生态学基本理论的认识。