红树林湿地生态系统中MCG古菌多样性和丰度的时空变化规律及其环境效应研究

Miscellaneous Crenarchaeota Group (MCG, recently named as “Candidatus Bathyarchaeota”) are one of widespread, diverse and predominant active archaeal groups in marine sediments, which might play a significant role in global marine carbon cycling. However, little is known about the microbial ecology of MCG archaea in coastal environments, including mangrove ecosystems. In this project, we will investigate the diversity, abundance, temporal and spatial distribution, as well as environmental effects of MCG archaea in mangrove sediments. We will collect mangrove sediment samples from two distinctive seasons (winter and summer) at different sediment layers to monitor various environmental parameters for background information. Then we will investigate the diversity, abundance and their temporal and spatial variation of MCG archaea in the samples, using Illumina Miseq high throughput sequencing, clone library, quantitative PCR (qPCR) and fluorescence in situ hybridization (FISH) technologies. We will also perform statistical analysis based on geochemical and microbiological results above, using different kind of software packages, such as Unifrac, CANOCO 4.5, and LINKTREE, to analyze the relationships between environmental factors and different subgroups of MCG archaea in mangrove sediments, thus we could understand how MCG archaea response to the environmental changing in coastal environments and evaluate their potential environmental effects. The results of this proposal will provide a insightful understanding on microbial ecology of MCG archaea in mangrove ecosystems, which not only enhances the knowledge of MCG archaea, but also provides scientific information on the sustainable development of coastal environments.

MCG (Miscellaneous Crenarchaeotal Group)古菌，又名深古菌，广泛分布在海洋沉积物中，是海底深部生物圈中最丰富且最活跃的微生物类群之一，对海洋碳循环具有不可忽视的贡献。本课题拟以红树林湿地生态系统中的MCG古菌为对象，研究其多样性和丰度的时空变化规律以及它们的环境效应。申请人将在深圳红树林湿地设置不同站位，分别采集不同季节和深度的沉积物样品，采用高通量测序、克隆文库、 定量PCR和荧光原位杂交等技术分析其中MCG古菌多样性和丰度的时空变化规律；结合环境参数和分子生物学的研究结果，利用统计学方法分析不同类群的MCG古菌与环境因子之间的内在关系，探讨它们对环境变化的响应和适应机制，并评估它们的环境效应。研究结果不仅可以丰富人们对MCG古菌的科学认识，还能增进人们对近海生态系统变化与环境变迁的认识，为近海海洋环境保护提供科学依据。

MCG（Miscellaneous Crenarchaeotal Group）古菌，又名深古菌（Bathyarchaeota），在海洋沉积物中数量巨大、代谢多样性极高，被视为海底深部生物圈中最丰富活跃的微生物类群之一。最新研究发现，MCG古菌不仅可降解包括蛋白质和芳香类化合物等各类有机物，还可能直接参与甲烷代谢和乙酸的产生，表明它们在海洋碳循环扮演不可忽视或不可替代的角色。目前MCG古菌的研究主要集中于大洋深海和个别河口近岸的沉积物，对其在近海生态系统中的生态功能的报道还非常有限。本研究结合分子生物学、生态学、基因组学和分析化学等交叉学科的技术手段，研究深圳周边滨海红树林湿地中 MCG古菌的种群结构、功能及生态效应，并考察 MCG 古菌对环境变化的响应与适应机制。主要研究结果包括（1）分析了深圳湾红树林湿地两个季度不同层次沉积物中总古菌多样性和丰度变化，发现MCG古菌、MBG-D菌、洛基古菌和乌斯古菌是最主要的四大类古菌；其中MCG古菌其相对占总古菌的43.32%，其丰度随沉积物深度增加而逐渐增加；（2）在红树林湿地沉积物共发现至少17个不同亚群的MCG古菌，其中亚群6、8、15和17为主要类群；（3）相关性分析发现，季节对MCG古菌的多样性组成和丰度的影响不显著，总有机碳和NO与MCG古菌的丰度有显著相关关系，而pH则是影响MCG古菌群落结构的最重要的环境参数，其中亚群6的生态分布和环境参数的关系与其他亚群有显著差别，表明该亚群更偏好分布于微酸、高有机碳和厌氧环境，具有独特的生理代谢机制；（4）对所构建的6个几乎完整的MCG古菌的基因组和转录组开展系统分析，揭示了它们多样化的碳代谢途径，暗示这些古菌对于沉积物碳循环具有不可忽视的贡献。上述研究成结果累计发表7 篇直接相关的学术论文，包括1篇发表于Nature Microbiology和 1篇发表于FEMS Microbiology Reviews的高水平学术论文。这些研究成果系统的阐述了红树林湿地生态系统中MCG古菌多样性和丰度的时空变化规律，揭示了MCG古菌的生理代谢潜能并评估了MCG古菌的环境效应，对于推动MCG古菌这一刚刚兴起的领域的深入开展具有重要的理论意义。此外，另有10篇间接相关的学术论文也获得了本项目的大力支持，在论文发表时均给予诚挚的致谢。