弧菌在我国边缘海的生态分布及在碳循环中的作用研究

Heterotrophic microorganisms are known to play key roles in driving remineralization of organic carbon. However, the degradation and transformation processes and mechanisms on organic carbon as well as the contribution to organic carbon remineralization of most microbial groups are poorly understood, which hinders our understanding of marine carbon cycle. The study object of this project is Vibrio species, a widespread bacterial species in marginal seas with high abundance and heterotrophic metabolic activities. The abundance, species composition and genetic diversity of Vibrio species in different environments of Chinese marginal seas will be investigated, and their distribution patterns in Chinese marginal seas will be determined; the correlation between geographic distribution patterns as well as population genetics properties of Vibrio species and various environmental factors will be analyzed, and the main control factors that affect the distribution and ecological roles exertion of Vibrio species will be discovered; degradation efficiencies of Vibrio species on different types of organic carbons will be tested, and the contribution of Vibrio species in degradation of marine organic carbon will be revealed; genes encoding hydrolytic enzymes to typical organic carbon will be cloned and heterologous expressed, the degradation activity will be detected and the hydrolysed product will be identified, and the degradation mechanism of Vibrio species to typical organic carbon will be revealed. Finally, all the results will be combined, and the roles of Vibrio species on carbon cycle of Chinese marginal seas will be evaluated. Based on the above studies, the knowledge of the contribution of heterotrophic microbial communities to carbon cycle in marginal seas will be enriched.

异养微生物在驱动有机碳矿化过程中发挥着关键作用，但目前绝大多数微生物类群对有机碳的降解转化过程和机制以及对有机碳矿化的贡献尚不明确，阻碍了人们对海洋碳循环的认识。本项目拟以边缘海中分布广、丰度高且异养代谢活性强的弧菌为研究对象，通过对其在我国边缘海不同环境中的丰度、种类组成和遗传多样性等方面进行研究，阐明弧菌在我国边缘海的分布规律；通过对弧菌地理分布特征和种群遗传学特征与环境因素的相关性分析，找出影响弧菌分布及其生态功能的主控因子；通过检测弧菌对不同类型有机物的降解效率，揭示其在海洋有机碳降解过程中的贡献；通过对典型有机物降解酶基因进行异源表达、降解活性及降解产物的检测，揭示弧菌对有机碳的降解机制。最后，结合弧菌生态分布等的研究结果，估算弧菌在我国边缘海碳循环中的贡献。通过以上研究，加深人们对异养微生物在边缘海碳循环中所发挥作用的认知。

异养微生物在驱动有机碳矿化中发挥关键作用，但人们对于异养微生物对有机碳的降解过程和机制及其对有机碳矿化的贡献了解甚少，阻碍了对海洋碳循环的认识。本项目拟以边缘海中分布广、丰度高且异养代谢活性强的弧菌为研究对象，通过对弧菌在我国边缘海的丰度、种类组成、种群遗传学特征、环境响应以及对典型有机物的降解过程和机制等进行研究，阐明其生态分布特征及在碳循环中的作用。研究结果表明，我国边缘海（渤海、黄海、东海、南海及长江口）水体和沉积物中的弧菌丰度高于全球其他海域；弧菌丰度呈显著的时空差异，夏季＞冬季，沉积物>水体，海水>淡水，南海>黄海，弧菌呈自由生活或颗粒附着状态；冬季和夏季的优势类群分别为大西洋弧菌和欧文氏弧菌。弧菌分布呈明显的空间异质性和距离衰减模式，受温度、盐度、DO、pH及空间因素等的显著影响。弧菌拥有稳定的核心基因组与趋近无穷大的泛基因组，使其适应多变的海洋环境，弧菌祖先坎贝氏弧菌可能从~385百万年前泥盆纪时期伴随鱼类的繁荣一同出现；几丁质酶基因在弧菌基因组中广泛存在，说明几丁质对弧菌生存非常重要；分离自不同生态位的坎贝氏弧菌具有显著不同的有机物降解基因和遗传特性，说明环境因素对弧菌生态功能具有重要控制作用。发现弧菌对多种大分子有机物有降解作用，但不同菌株的有机物降解谱有较大差异，多数菌株可降解几丁质，许多菌株可降解褐藻胶；发现轮虫弧菌和哈维氏弧菌中两个序列高度相似的几丁质酶具有截然不同的酶学性质；从海弧菌中鉴定出10个褐藻胶裂解酶基因，其中2个为新酶基因，该菌基因组具有3个褐藻胶代谢基因座，该菌在降解褐藻胶过程中会分泌囊泡结构，内含褐藻胶裂解酶，提出了细菌褐藻胶降解代谢的新思路。总之，本项目揭示了弧菌在我国边缘海的生态分布特征、环境因素对弧菌地理分布和生态功能的控制作用及其对不同类型海洋有机碳的降解过程和机制，加深了人们对异养微生物在边缘海碳循环中所发挥作用的认知。