近海与河口MGII古菌的碳代谢机制及其群落互作关系的研究

Archaea comprise 20% of the total prokaryotic biomass in ocean water and play critical roles in the global carbon cycle. MGII archaea are one of the two predominant planktonic archaeal groups in the ocean. They widely distribute in diverse marine environments and are especially abundant in coastal waters and estuaries, serving as key players in organic carbon degradation and sequestration. However, we have limited knowledge about the community composition of MGII archaea in coast waters and estuaries, their interactions with the environment, and their carbon metabolism pathways. Based on our previous findings, we propose in this study the hypothesis that MGII archaea adapt to highly dynamic coastal and estuarial environments by forming a mutualistic relationship with algae. The core scientific questions include 1) the distributional pattern of MGII archaea and environmental factors controlling or affecting it in Chinese estuaries and adjacent seas; 2) the symbiotic mechanism between MGII archaea and algae; and 3) the metabolic rate of organic carbon utilization by MGII archaea. We plan to conduct extensive sample collection and cultivation, utilize state-of-the-art technologies such as metagenomics/transcriptomics, single-cell Raman spectrum and high-throughput cell enrichment and isolation, and combine with bioinformatic methods, to systematically analyze and validate the above hypothesis and to subsequently answer those core scientific questions. This study will provide fundamental data and theoretical basis for assessing MGII archaea’s contribution in coastal and estuarial carbon cycling, restoration of coastal ecosystems and mitigation of global climate change.

古菌占海洋水体原核生物总量的20%，在海洋碳循环过程中发挥着重要作用。MGII是海洋水体中两大主要古菌类群之一，广泛分布于各种海洋环境，在近海与河口尤其丰富，是有机碳降解过程的重要参与者。然而，对MGII古菌在近海与河口的群落组成、环境互作机制及碳代谢过程仍知之甚少。本项目在前期研究基础上，首次提出“MGII与藻类互惠共生以适应近海与河口动态变化环境”的科学假说，其核心科学问题是：1、近海与河口MGII的分布规律及受控因素；2、MGII与藻类共生长的过程和机制；3、MGII代谢有机碳速率的量化分析。通过大量样品采集和富集培养，采用宏基因组/转录组、单细胞拉曼光谱以及高通量富集分离等先进技术，结合生物信息学方法，综合分析和系统验证该科学假说以达到揭示上述科学问题的目的。本项目成果将为评估MGII对近海与河口有机碳循环的贡献、改善近海生态环境及应对全球气候变化提供重要的基础数据和理论依据。

海洋浮游古菌是海洋水体中非常丰富的微生物类群，在全球碳循环中起着重要的作用。它们主要由MGI和MGII组成。目前MGI已有纯培养，且其生态分布、生理生化和演化都有较多研究报道。然而，对MGII古菌在近海与河口的群落组成、环境互作机制及碳代谢过程仍知之甚少。本研究通过生态调查技术、无人机采样技术、海洋化学、分子生物学、微生物学、拉曼光谱技术和生物信息学技术等多种先进方法研究了珠江口、南海北部等海域的样品中的MGII古菌分布及其与浮游藻类种群的相互作用、盐度变化驱动的全球河口环境MGII物种分化及演化路径、MGII的富集培养和基于拉曼光谱的MGII生理生化研究。取得了以下重要成果：1）珠江口和南海北部的浮游藻类种群对MGII古菌分布和生态位物种具有潜在调控影响；浮游植物可能是影响MGII古菌分布和活性的重要因素；2）无人机高密度采样技术揭示昼夜节律微生物主要为光合自养藻；部分异养细菌也具有微弱的昼夜节律，而古菌无明显昼夜节律；3）通过研究盐度变化驱动的全球河口环境MGII物种分化及演化路径，提出了MGII在半咸水和海水之间的分化是由全球地质背景下一个镁运输基因corA的重新排列引发的假说；4）建立了稳定传代的MGII富集培养体系且通过组学数据进一步拓展了MGII系统发育树；完整闭环基因组图谱展示了具有固碳潜力的MGII新类群MGII-CF；5）通过拉曼光谱和荧光原位杂交联用方法研究了MGII的生理生化，揭示了MGII可能具有潜在的脂肪酸合成或代谢通路。在项目执行期间：1）已发表论文39篇, 其中SCI论文35篇, 获批中国实用新型专利4项，申请发明专利2项； 2）举办2次国际会议和5次国内会议；3）共培养4位博士后，3位博士研究生和5位硕士研究生。项目执行率为87.54%