沉水植物根际反硝化菌-厌氧氨氧化菌耦合分子生态效应研究

The discovery of anammox in the ocean has profoundly changed our understanding of the nitrogen cycle in the environment. At the same time, the study of anammox in the freshwater is becoming a new rising research field. With the help of our previous research project, the anammox bacteria were found to exist extensively in lake sediments of the Jianghan Plain. And there was a positive correlation between denitrification and anammox (P<0.01), which means that these two reactions have the coupling effect. Unfortunately, researchers know nearly nothing about this effect. Submerged plant holds a dominant status in the lake ecosystem and its rhizosphere is the most active area of nitrogen cycle. It is helpful for understanding of inherent mechanism of the coupling effect to study microorganisms of the nitrogen removal process in this rhizosphere area. The actual field survey and the test of rhizosphere incubator will be carried out in our research. These studies can help analyzing the molecular coupling process of denitrifying bacteria and anammox bacteria in the rhizosphere area by means of the molecular ecology technology, in situ microelectrode determination method and serial section of quick-frozen soil. Furthermore, the research will reveal the evolution mechanism of two kinds of microorganisms and main influencing factors in nitrogen removal process. Research results can develop theory of nitrogen cycle in lake and provide a scientific basis for the bioremediation of polluted water.

海洋中厌氧氨氧化的发现已深刻改变了人们对海洋氮素循环的认识，淡水湖泊的厌氧氨氧化研究也正在快速兴起。依托上一基金，申请人发现厌氧氨氧化菌在江汉平原湖泊中广泛存在。且反硝化反应和厌氧氨氧化反应间存在正相关关系（P<0.01）,两种脱氮反应存在耦合效应，但这种效应的过程和机制还不清楚。沉水植物在湖泊生态系统中具有主导地位，根际氮素循环活跃，对其脱氮微生物进行研究，能更准确地揭示耦合效应的内在机理。本项目拟通过植物根际野外调研和根际培养箱实验，采用分子生态学、微电极原位测定、土壤速冻切片等技术，从分子生物学角度探索沉水植物根际反硝化菌与厌氧氨氧化菌的耦合过程，揭示这两类脱氮菌种群关系演变机制及主要影响因素。研究结果可丰富湖泊氮素循环理论，并为水体生物修复提供科学依据。

反硝化菌可为厌氧氨氧化菌提供反应物NO2--N，但同时也与厌氧氨氧化菌竞争NH4+-N，这两种微生物间存在着复杂的竞争协作关系。本项目通过野外采样和室内培养相结合的方法，从分子生物学角度探索了沉水植物根际反硝化菌与厌氧氨氧化菌的耦合过程。研究表明在长江中游典型湖泊沉水植物根际中，Candidatus Kuenenia属的厌氧氨氧化菌占有优势地位。根区和非根际环境更有利于nirS型反硝化菌和厌氧氨氧化菌的生长，而根际环境则对这两种菌生长产生了抑制作用。进一步研究表明，随植物生长时间的增加，根际NirS型反硝化菌数量与厌氧氨氧化菌数量的比值趋于平稳，植物生长减缓了这两种微生物的竞争关系。根际反硝化菌数量会随遮光度的增大而增加，而厌氧氨氧化菌数量却未表现出明显波动，遮光改变了两种菌间的种群动态关系。沉水植物受损或者死亡后，根际反硝化菌数量和厌氧氨氧化菌的丰度都会下降，但两者的下降程度存在差异性。本项目研究成果有助于深入了解湖泊氮素循环过程，并为水体修复提供了一定的科学依据。