Geobacteraceae-Methanogens种群间的电子传递过程及对湿地土壤甲烷释放的影响机制

Methane is an important greenhouse gas and terrestrial wetlands, including natural wetlands and rice paddies, contribute about half of the global methane emissions. There was a significant increase in methane that could be attributed to increased release of methane from northern wetlands in 2007 and tropical wetlands in 2008. Syntrophic interactions between microorganisms are essential for microbial methane production, however,these syntrophic interactions are poorly understood and there is insufficient information to predicatively model how electron transfer will influence these interactions and methane production. In present project, we propose to elucidate key syntrophic interactions associated with the production of methane in wetlands.The proposed research will coculture Geobacteraceae and Methanogens to test whether direct cell to cell electron transfer between Geobacteraceae and Methanogens; to analysis members of syntrophic methanogenic cultures optimize cell-to-cell electron transfer by conductive pili or other outer-surface components that promote direct cell-to-cell electron. Some wetlands soils in Fujian Province will be sampled to characterize the mode of electron transfer of Methanogens. The researches will analysis the community composition of Geobacteraceae and Methanogens in wetlands soil aggregates and determine the construction, function conduction of soil aggregates and its effect on methane production. This research is expected to provide new insights into the mechanisms of syntrophy and represents an important first step in developing the capacity to predictively model the contributions and response of methanogenic microbial communities to global carbon cycling and climate change.

甲烷作为仅次于二氧化碳的全球第二大温室气体，对全球温室效应产生重要影响。湿地环境中微生物互营产甲烷过程介导着甲烷的生物地球化学循环，由于环境介质和环境条件的复杂性，种群互营关系的核心-电子传递过程一直没有得到清晰的认识。本项目拟以我国典型亚热带湿地土壤为代表原位样品，结合室内模拟实验，以湿地环境中典型Geobacteraceae和Methanogens微生物为代表互营共培养，阐明微生物种群间电子传递模式；分析其直接电子传递的可能性及对产甲烷过程的影响；在分子水平上研究湿地不同粒径土壤颗粒上Geobacteraceae和Methanogens组成与分布；湿地土壤颗粒的结构、功能和导电性及可能的电子传递模式与产甲烷过程的耦联关系；阐明湿地土壤中Geobacteraceae-Methanogens种群间的电子传递及对湿地土壤甲烷释放的影响机制，为湿地甲烷释放过程的控制以及有机碳循环提供理论。

甲烷作为第二大温室气体和新能源，对全球温室效应以及经济产生重要影响。种间电子传递是厌氧产甲烷过程的核心。本项目以我国亚热带湿地土壤和UASB厌氧颗粒污泥开展室内模拟实验，同时构建厌氧产甲烷互营共培养体系，分析了产甲烷颗粒上Geobacteraceae和Methanogens组成与分布、功能和导电性及可能的电子传递模式与产甲烷过程的耦联关系，取得主要进展如下：.1、阐明了厌氧产甲烷体系co-culture系统产甲烷过程及电子传递模式。项目组构建了Desulfovibrio vulgaris 和Geobacter sulfurreducens WT（Geobacter sulfurreducens hyb突变株）共培养体系并证明其种间氢转移机制。同时也成功构建Desulfovibrio sp和 Methanosarcina sp共培养体系。基于前期的成果，我们在Renewable & Sustainable Energy Reviews（IF 6.798）上发表了目前的种间电子传递包括种间氢气转移、种间甲酸转移和种间直接电子传递（DIET）等三种方式的可能过程与机制的综述文章。.2、建立了湿地土壤与UASB厌氧产甲烷体系颗粒微生物组成、导电性与电子传递模式的关系。确定了产甲烷颗粒导电性和微生物纳米导线pili的分析方法，发现湿地土壤与UASB厌氧产甲烷体系中导电性与甲烷转化率相关性显著，而且导电性与关键微生物种群Geobacter和Methanosaetae的数量显著线性相关，初步证实了体系种间直接电子传递的可能性。.3、阐明了外源材料影响产甲烷过程电子传递模式与效率的机制。研究发现活性炭能有效促进共培养体系及湿地土壤和UASB颗粒污泥反应器的甲烷产生效率，通过转录组高通量测序发现共培养体系微生物电子传递链相关基因的表达量发生显著变化，活性炭的添加强化了电子传递链中Qrc路径，从而促进了该互营体系的电子传递速率，而且发现体系的导电性明显增加，这样活性炭的加入有可能促进DIET从而影响产甲烷过程与效率。.项目组经过四年的努力，初步阐明了湿地土壤体系和UASB反应器中厌氧产甲烷过程颗粒的导电特性及关键微生物种群电子传递模式，为厌氧产甲烷过程提供了理论依据。项目负责人以第一作者或通讯作者发表SCI收录文章10篇文章（其中影响因子大于4的有7篇）。