深渊海沟是海洋最深处，具典型的“漏斗”地貌，孕育了独特的异养型细菌占主导的微生物群落。黄杆菌纲是深渊异养细菌的代表类群，但其生理代谢活性高度不明。申请人初步研究发现Mesoflavibacter是深渊黄杆菌纲的优势属，本项目拟以该属细菌为代表，深入探究深渊黄杆菌纲的有机质代谢能力及作用机制，以提升对深渊微生物所发挥生态作用的认识。采用培养/非培养方法，分析以马里亚纳海沟为代表的深渊生境中黄杆菌纲的多样性及有机质利用遗传特征；获得Mesoflavibacter菌株及基因组，通过比较基因组及底物培养实验，鉴定深渊该属细菌的优势/特有有机质代谢基因，揭示其有机质利用能力，并结合转录组/蛋白质组及碳水化合物活性酶功能分析，解析其对以多糖为代表的有机质的代谢通路；同时，分析深渊该属细菌有机质代谢基因的进化路径和环境响应。本研究将深化对深渊生命过程的认知，促进对海洋异养微生物代谢有机质过程机制的理解。

The hadal trench is the deepest ocean on Earth featured by funnel-shaped geomorphology and unique microbial communities that are dominated by heterotrophic bacteria. Flavobacteriia, a class of heterotrophic bacteria, is predominant in the hadal water, but its physiological and metabolic properties are largely unknown. Our preliminary results revealed that Mesoflavibacter was a representative genus of hadal Flavobacteriia. In this proposal, the organic matter utilization capability and mechanism of Mesoflavibacter will be investigated to gain insights into the ecological role of hadal microorganisms. By using both culture-dependent and -independent methods, the species diversity and genetic basis of organic utilization in Flavobacteriia in the hadal environment (the Mariana Trench) will be investigated. Isolates and genomic sequences of Mesoflavibacter will be obtained. A combination of comparative genomics, substrate utilization experiment, transcriptomic/proteomic analysis and carbohydrate-active enzyme expression and characterization will be implemented to identify the dominant/unique organic matter metabolic genes of hadal Mesoflavibacter, to reveal its capability of organic matter utilization, and to elucidate its organic matter utilization pathway (represented by polysaccharides). Moreover, the evolutionary path and environmental response of organic matter utilization genes in hadal Mesoflavibacter will be analyzed. This study would provide insights into the hadal life process and strengthen our understanding of the process and mechanism of organic matter unitization by marine heterotrophic microorganisms.