深渊海沟沉积物中古菌群落的生态分布特点及其碳氮代谢机制研究—以雅浦海沟为例

The hadal trench is characterized by the ultra-high pressure, isolated environment, and funneling effect. It contains abundant, active, and special forms of extremophiles. Latest studies have revealed that archaeal communities play important roles in hadal sediments, but the mechanism of how they drive carbon and nitrogen metabolism in hadal sediments is still unclear. Our previous metagenomic analysis reveals that higher abundances of archaea and amoA genes, and the complete archaeal HP/HB cycle were detected in the surface sediments of the Yap Trench. Therefore, we propose the hypothesis that archaeal communities, as represented by Thaumarchaeota, play important roles in the carbon and nitrogen cycles in hadal trench sediments. In this proposal, we aim to investigate the correlation between archaeal communities and environmental parameters from different layers in the Yap Trench sediments, by using high-throughput sequencing and statistical analysis. Then we will reveal the metabolic pathways of carbon and nitrogen for major archaeal communities by using metagenomics and metatranscriptomics. Finally, we will provide insight into the carbon and nitrogen metabolism of archaeal communities in hadal sediments, by stable-isotope-probing approaches, simulated culture systems, and isolation of pure archaeal cultures with carbon and nitrogen activities. This study may also find some special archaeal groups, and their new metabolic pathways and regulatory mechanisms from this hadal extreme environment.

深渊海沟具有超高压、封闭性和漏斗效应的特点，蕴育着丰富、活跃且特殊的极端生命形式。最新的研究表明，古菌在深渊沉积物中占据重要地位，然而它们如何驱动深渊沉积物的碳氮代谢的机制目前还不清楚。申请人前期通过宏基因组分析发现，雅浦海沟的表层沉积物中含有高丰度的奇古菌和古菌amoA基因，并含有完整的古菌HP/HB固碳途径。因此，我们提出科学假设：以奇古菌为代表的古菌在深渊海沟沉积物的碳氮循环过程中具有重要的作用。为证明该科学假设，本项目以雅浦海沟沉积物中的古菌为研究对象，先通过高通量测序和统计学分析评估不同层位的沉积物中的古菌类群与各种环境参数的相关关系，再采用宏基因组和宏转录组手段揭示主要的古菌类群的碳氮代谢途径，最后设立稳定同位素标记的模拟培养系统、分离具有碳氮代谢活性的纯培养古菌来进一步探讨深渊沉积物古菌的碳氮代谢机制。该研究还有望从深渊极端环境中发现特殊的古菌类群及其新的代谢途径和调控机制。

深渊生物圈一般是指水深大于6000米的海沟区域，它占据海洋垂直深度梯度的45%，具有高静水压、低温和封闭性的特点。前期研究集中于阐述深渊水体和沉积物中微生物群落的丰度和多样性，但是对深渊中的微生物参与的碳氮循环过程的研究较少。本项目以雅浦海沟和马里亚纳海沟为研究对象，聚焦于深渊环境中的微生物参与的碳氮代谢过程及其环境适应性机制，目前已取得以下3项研究成果：（1）揭示了深渊海沟中微生物群落的碳氮代谢特点，并以中国神话人物中海龙王的形象命名了3个全新的细菌门类，彰显了中国文化自信，进一步拓展对深渊微生物的认知。（2）详细报道了底栖古菌含有一套非常古老的氢酶呼吸系统，丰富了古菌的呼吸系统的进化历史。（3）系统综述了古菌在滨海生态系统的碳循环过程发挥的重要作用，激发了人们对如何利用古菌来减缓气候变化的研究兴趣。本项目研究紧紧围绕水圈微生物重大研究计划的重点资助方向（一），为揭示大洋重要微生物功能类群及其驱动碳氮硫循环的机制提供更丰富的科学证据。