深海黑暗食物链的发现，打破“万物生长靠太阳”的传统观念。作为深海中广泛分布的化能自养微生物，奇古菌所主导的硝化反应在深海黑暗食物链中是初级生产力的重要贡献者。但是这些深海奇古菌目前还没有被分离和培养，它们所参与的碳氮转化过程仍然不清楚。本项目前期实验发现南海深层水中添加氨后，可持续产生亚硝酸，推测氨是限制深海奇古菌生长的关键因素，从而提出“深海奇古菌在黑暗食物链中作为初级生产力受制于氨来源”的科学假设，其核心科学问题是：1）深海奇古菌获取氨的内在分子机制；2）深海奇古菌在黑暗食物链中对宏观初级生产力的贡献。本项目拟通过建立深海奇古培养体系，获得其富集物，并综合利用微生物学、海洋生态学、生物地球化学等多学科手段，结合基因组模型算法，揭示深海奇古菌的转化碳氮元素的过程与机制，验证该科学假设以揭示上述科学问题。本项目成果将为理解深海碳循环过程及黑暗食物链的驱动机制提供基础数据和理论依据。

The discovery of the deep-sea dark food chain breaks the traditional concept of "all things grow by the sun". As a wide range of chemoautotrophic microorganisms distributed in the deep sea, Thaumarchaeota performing the limiting step of nitrification make significant contributions to the primary production in the deep-sea dark food chain. However, the detailed mechanisms of nitrification and CO2 fixation performed by these deep sea Thauharchaeota have not been elucidated. Our preliminary experiments showed continuous production of nitrite after adding ammonia in the cultivation systems using the deep water of the South China Sea. Thus our hypothesis for this project is that the deep-sea Thaumarchaeota performing CO2 fixation in the dark food chain is constrained by the availability of ammonium in deep sea. The core scientific issues include: 1) the intrinsic molecular mechanisms of ammonia-acquisition by deep sea Thaumarchaeota; 2) the macro-scale contribution of deep-sea thamarchaeota to the primary production in the dark food chain. This project intends to address these fundamental questions using enrichment cultures of deep-sea thaumarchaeota from South China Sea. Through comprehensively multi-disciplinary methods such as microbial genomics, marine ecology, biogeochemistry, and genetic modelling, we will be able to reveal the process and mechanisms of nitrification and the carbon transformation conducted by the deep-sea Thaumarchaeota, which would verify the above hypothesis and address scientific questions. The results of this project will provide basic data and theoretical basis for the deep-sea carbon cycling and the driving mechanism of the dark food chain.