东北农田黑土氮循环关键过程微生物的地理分布及其驱动机制

Surveys of spatial distribution patterns of microbial community diversity and composition and the factors driving such patterns is indispensable to understand the biological diversity and maintain mechanism. Recently, the researches on soil microbial distribution patterns and their driving force going very rapidly, many research pointed out that microbial communities were geographically distributed and the hypothesis of the microbial random distribution pattern has been ruled out. Although few studies analyzed the distribution patterns on microbial functional genes, their maintain mechanism are still unclear. Therefore we currently know little regarding the distribution patterns of microbial functional traits in nature. Black soils (Mollisols) are one of the most important soil resources for maintaining food security of China and are mainly distributed in northeast China. To understand which environmental factors influence the microbial functional communities and how the communities are distributed in the black soils, we collected soil samples with different soil carbon contents across the black soil zone in northeast China. In this project, soil nitrifying and denitrifying community composition, the potential functional gene diversity and their distribution patterns will be analyzed by using clone library, Illumina MiSeq sequencing and GeoChip methods. Through this study, the changes of microbial functional genetic diversity and community structure with environments will be clarified; and the distribution patterns on microbial functional genes and those mechanisms alone the latitudinal gradient in the black soil zoon will be discovered. These studies are expected to provide scientific basis for understanding the biogeochemical cycling process mediated in soil microbe in farmland ecosystems.

微生物群落组成与多样性的空间分布格局及对环境因子梯度变化的响应研究，是揭示地球上生物多样性产生和维持机制的必要前提。近年来，土壤微生物的分布格局及其驱动机制研究成为国际上研究的重点，排除了微生物随机分布格局的假说，揭示出微生物群落存在明显的地理分布特征。然而，目前只有少数报道分析了微生物功能基因的空间分布模式，其形成机制尚不清楚。为此，本项目以我国东北黑土区纬度梯度样带的农田土壤为研究对象，利用构建克隆文库和高通量测序技术，研究参与农田土壤硝化和反硝化过程微生物种群、丰度和多样性分布特征。同时采用基因芯片技术探讨农田土壤微生物功能基因的空间分布规律。该研究将明确氮循环主要过程微生物的群落结构组成及分布，阐明我国东北黑土区农田土壤功能微生物的空间分布格局及其驱动机制，对认识土壤微生物参与的农田生态系统的生物地球化学循环过程提供理论基础。

土壤微生物群落组成和多样性的地带性分布特征及对环境因素梯度变化的响应机制研究，是揭示生物多样性的产生和维持机制的必要性前提。近年来，土壤微生物的分布格局及其驱动机制研究成为国际上研究的重点，排除了微生物随机分布格局的假说，揭示出微生物群落存在明显的地理分布特征。然而，目前只有少数报道分析了微生物功能基因的空间分布模式，其形成机制尚不清楚。本研究通过实时定量qPCR、扩增子和宏基因组学分析技术，明确了不同纬度梯度下土壤氨氧化细菌、古菌、固氮和反硝化微生物的丰度变化及分布特征，揭示了不同功能微生物的群落组成和演替规律。本项目研究发现，亚硝化球菌（Nitrososphaera）和亚硝化螺菌（Nitrosospira）分别是黑土农田土壤参与氨氧化过程的主要AOA和AOB类群，古菌群落中奇古菌（Thaumarchaeota）数量最多，其次是广古菌（Euryarchaeota），而泉古菌（Crenarchaeota）占比较低。奇古菌中Thaumarchaeota group 1.1b是最主要分布类群，鉴于Thaumarchaeota group 1.1b隶属于Nitrososphaera类群，说明黑土农田土壤中的大部分古菌均参与了氨氧化过程。大多数被检测到的反硝化微生物群落均属于未明确分类的微生物类群，其中有明确分类信息中Rhodanobacter的相对丰度最高，其次为Bradyrhizobium。此外，基于定量qPCR耦合氮循环关键过程微生物丰度及宏基因组分析，揭示出不同氮循环过程的基因演替规律，研究发现农田土壤氮循环微生物具有明显的地理分布特征，其中土壤pH是驱动两类氨氧化微生物和反硝化微生物空间分布的最主要的土壤因子，此外不同氮循环过程关键基因同时也受到有机质和全氮含量的影响，但不同氮循环过程微生物受到地理分割和环境因子影响的相对贡献不尽相同。