海洋沉积物中甲烷代谢微生物的研究进展

Advances in the study of methane-metabolizing microbial communities in marine sediments

甲烷是一种重要的温室气体,深刻影响着全球的气候变化。同时,甲烷还是海底潜在能源—天然气水合物的主要成分。海洋沉积物是甲烷生物转化的一个重要生态区域,产甲烷菌主要利用H_(2)、CO_(2)及简单的有机物(甲醇、甲胺、二甲基硫等)作为底物生成甲烷,产生的甲烷在向上迁移的过程中主要被甲烷厌氧氧化(anaerobic oxidation of methane, AOM)和甲烷好氧氧化(aerobic oxidation of methane,AeOM)消耗,进而大大减少了甲烷向大气的排放量。AeOM主要发生在含氧的沉积物及沉积物-水界面中,由甲烷好氧氧化菌(aerobic methane-oxidizing bacteria, MOB)介导。然而,绝大部分甲烷在穿透缺氧沉积物层之前是被AOM反应消耗,甲烷厌氧氧化古菌(anaerobic methanotrophic archaea,ANME)是主要的参与者,这些功能微生物耦联电子受体SO_(4)^(2-)、NO_(2)^(-)/NO_(3)^(-)或Fe^(3+)和Mn^(4+)将甲烷进行氧化。本文对产甲烷菌和甲烷氧化菌的种类、代谢途径及其在海洋沉积物中的分布特征进行了综述,并在前人工作基础上,对今后海洋生境中甲烷代谢过程的研究进行了展望,以期为进一步开展海洋环境中甲烷的生物转化过程及元素耦合的研究提供理论依据。

Methane is an important greenhouse gas affecting the global climate. Meanwhile, methane is a major component of natural gas hydrate which regarded as a potential energy resource below seafloor. Seafloor sediment is an important ecological region for methane biotransformation. The methanogens can use H_(2), CO_(2), and simple organic compounds(e.g. methanol, methylamines, dimethylsulfide) as substrates to produce methane. The methane produced in the bottom of the sediments would be consumed by aerobic methanotrophs and anaerobic methanotrophs during its upward migration, which reduces greatly the methane emissions to the atmosphere. Aerobic methane oxidation occurs mainly in oxygenated sediments and sediment-water interfaces, and is mediated by aerobic methane-oxidizing bacteria.However, most of the methane is consumed by anaerobic methane oxidation before it reaches the seafloor. The anaerobic methanotrophs oxidize methane coupled by SO_(4)^(2-), NO_(2)^(-)/NO_(3)^(-)or Fe^(3+)/Mn^(4+). We reviewed the status quo and perspectives of the taxonomy, metabolic and ecological diversity of methanogens and methanotrophs in marine sediments, and emphasized deficiencies and issues need to be solved in future studies.This review provided theoretical foundation for the study of biotransformation process and element coupling of methane in marine environment.