厌氧铁氨氧化反应在南方湿地生态系统中的分布及其对氨氧化的影响

Recently, a novel ammonium oxidation process under iron reduction (Feammox) has been described and a previously unreported species Acidimicrobiaceae bacterium A6 are suggested to play an important role in Feammox process. The discovery of Feammox makes us believe the previous natural ammonium oxidation was underestimated, particularly in the region with environmental factors (low pH, rich iron, vegetation, etc) that suitable for Feammox, such as wetlands in Southern China. Thus, the purpose of this project is to discover and evaluate Feammox in this region. We will take soil samples from typical wetlands, including tropical and subtropical wetlands, natural and engineered wetlands, coastal wetlands and freshwater wetlands, and vegetation will be considered like mangrove and other forest wetlands. From each wetland, the Feammox process will be measured by 15N isotope incubation. Feammox bacteria and the microbial community will be assessed by qPCR and 454 pyrosequencing, which will help to understand the cooperation and competition of Feammox and other bacteria. The interactions of Feammox and other nitrogen-transformed bacteria and their effects on nitrous oxide will be assessed as well. Finally, based on these studies, the evaluation of Feammox on ammonium oxidation as well as nitrogen cycle within wetlands in Southern China will be achieved. This project will provide insight into Feammox and its contribution to the nitrogen cycle in Southern China, and will allow for further manipulation of the Feammox pathway in soil environments and/or engineered treatment systems.

厌氧铁氨氧化（简称铁氨氧化）反应是一种新发现的氮循环途径，它是以三价铁作为电子受体，氨作为电子供体，在缺氧条件下完成氨氧化生成亚硝酸盐的过程。铁氨氧化细菌是铁氨氧化的参与者，它主要存在于富含铁、低pH、含植物根系的土壤环境中。我国南方湿地生态系统满足铁氨氧化细菌生长所需条件，同时项目组的前期工作结果显示广东韶关地区存在铁氨氧化细菌，因此我们推测铁氨氧化很可能成为南方湿地生态系统中氨氧化的一个重要反应。根据前期工作结果，本项目拟扩大采样区域，研究铁氨氧化反应在多种南方湿地生态系统中的分布和对当地氨氧化的贡献值，探索铁氨氧化反应所发生的细菌群落特征以判断铁氨氧化细菌与其他微生物的合作竞争机制，探讨铁氨氧化对温室气体氧化亚氮释放的影响机理，从而对铁氨氧化在南方湿地中的贡献值提出总体评价，并为下一步利用铁铵氨化处理作为湿地氮去除系统提供理论依据。

厌氧铁氨氧化反应是一种新发现的氮循环途径，它是以三价铁作为电子受体，氨作为电子供体，在缺氧条件下完成氨氧化生成亚硝酸盐的过程。本项目一方面富集并分析厌氧铁氨氧化细菌，另一方面扩大采样区域，在矿山区域、河流沉积物、水稻土、人工湿地、种植菜地、电子拆解园等土壤采样，通过培养实验、高通量测序、分子生物学分析等手段，在kingdom，phylum，class，order，family，genus，species等各水平上分析微生物细菌群落结构组成，逐一分析厌氧铁氨氧化细菌与其它氮转化细菌之间的竞争与合作关系，并评价了厌氧铁氨氧化的重要性。结果表明：（1）经过培养，大宝山厌氧铁氨氧化细菌得到富集，其所在的class水平上Acidobacteria菌落所占百分比由原来0.058%上升至3.583%；电镜显示厌氧铁氨氧化菌为杆状菌。（2）在城市河流沉积物中，微生物在夏季活性高于冬季，且硝化细菌和反硝化细菌都受附近农业活动的影响。（3）在矿山区域、水稻土、人工湿地、种植菜地、电子拆解园等土壤类型采样，厌氧铁氨氧化细菌所在的order水平上unidentified_Acidimicrobiia所占比例为0.03%-1.46%，其中在矿山森林土的森林土或菜地土比例更高。（4）进一步对比（3）中genus水平上各类生态系统中微生物群落，尤其是各类硝化细菌的种类和数量比（好氧氨氧化菌，好氧氨氧化古菌，厌氧氨氧化菌，厌氧铁氨氧化菌，好氧亚硝酸盐氧化菌），各类氨氧化细菌占所有细菌比例的0.13%-1.46%，好氧亚硝酸盐氧化菌占所有细菌比例的0.05%-0.89%；其中厌氧铁氨氧化细菌一般占到各类氨氧化细菌总和的3%-10%；值得注意的是，高的厌氧铁氨氧化细菌群落出现在电子拆解园旁的菜地土（23.96%）和广西矿区外菜地土（99.29%），这显示了厌氧铁氨氧化细菌更为适应含重金属环境。本项目初步研究了厌氧铁氨氧化细菌在不同生态系统中的分布，初步评估了它在这几类生态系统中的地位，并初步分析了它所在的微生物菌落的组成。