全程硝化菌与其它硝化相关微生物在滩涂生态系统作用机制和相互关系的研究

The finding of complete ammonia oxidizer (Comammox) which oxidize ammonia to nitrate broke up our knowledge that nitrification is labour divided to ammonia oxidation and nitrite oxidation. Therefore, Comammox become hot issue in the research of ecological nitrogen cycle. The applicant found high ubiquity and diversity of Comammox in various environments including tidal flat, and already enriched and completely genome sequenced novel type of Comammox recently. In this project, we target Dongtan, Chongming at Yangtz River Estuary and coastal tidal flat at North Jiangsu Province, 1) analyze the distribution of Comammox and other nitrifiers in different ecological environments, and its correlation with environmental factors; 2）understand the contribution of Comammox in ammonia and nitrite oxidation, and the correlation with other nitrifiers based on microcosm tests of selected environmental samples; 3) enrich different types of Comammox, and understand the growth characteristics and active mechanism of Comammox based on batch and chemostat cultures of the enrichments at different condition. The study of active mechanism of Comammox and its correlation with other nitrifiers will accelate our understanding of nitrification process as an important part of the research of nitrogen cycle driven by microbes.

独自完成氨氧化和硝酸化过程的全程硝化菌的发现，打破了由两个不同类型微生物完成硝化过程的一百多年认识，全程硝化菌也已成为生态系统氮循环研究的新热点。申请人前期研究中发现全程硝化菌在滩涂等各种生态系统中广泛分布，而且已富集培养了还未报道的新型全程硝化菌，并完成了其全基因组分析。本研究中将以长江河口崇明东滩和苏北沿海滩涂为主要研究对象，分析滩涂不同生境中全程硝化菌和其它硝化相关微生物分布特点以及与环境因素的相关性；通过微宇宙培养实验，认识不同环境条件下全程硝化菌在氨氧化和硝酸化过程中的贡献以及与其它硝化相关微生物的关系；进一步富集培养不同类型全程硝化菌，通过摇瓶和恒化培养探讨其在不同环境条件下的生长特点和作用机制。滩涂生态系统中全程硝化菌与其它硝化相关微生物作用机制和相互关系的研究，作为微生物驱动氮循环机制研究的重要组成部分，必将促进人们对生态系统硝化过程的深入认识。

全程硝化菌的发现，让人们对氨氧化和硝酸化过程有了新的认识。本课题中我们设计针对Nitrospira属全程硝化菌clade A、clade B及针对传统硝酸化细菌的定量引物，使得可广泛应用于各种环境中这些微生物的丰度分析。基于宏基因组/转录组数据库，发现全程硝化菌主要分布在部分饮用水、河水、地下水和城市水道沉积物等中。探究了全程硝化菌在海岸带、长江口及不同季节和深度滩涂样品中的分布特点以及与其它硝化相关微生物和环境因子的关系。并选取滩涂生境样品开展微宇宙培养实验，并建立了水生环境中全程硝化菌活性贡献的研究方法，初步分析了盐度对全程硝化菌和其它硝化相关微生物活性和生态贡献的影响。此外，通过不断优化培养条件，我们从不同来源及不同盐度的样品中富集到了高比例的不同类型全程硝化菌，并通过添加不同抑制剂、改变环境因素等实验探究了全程硝化菌的生长特点、作用机制及培养过程中与其它硝化相关微生物的关系。上述结果有助于提升滩涂生境中全程硝化菌的贡献和作用机制及与其它硝化相关微生物关系的整体认识，并为开展其它生态系统中全程硝化菌的研究奠定了重要基础。