海洋沉积物中金属依赖型甲烷厌氧氧化作用研究进展及展望

Research progress and prospects of metal-dependent anaerobic methane oxidation in marine sediments

海洋沉积物中大部分甲烷会通过甲烷厌氧氧化作用(anaerobic oxidation of methane, AOM)而被消耗。早期研究表明,AOM可与硫酸盐、硝酸盐和亚硝酸盐的还原作用相耦合,从而有效减少甲烷向大气的排放。最近,金属依赖型AOM(metal-AOM,活性金属氧化物还原反应驱动的AOM)被证实存在于自然界沉积物和富集培养的样品中。但是,目前仍未从自然海洋环境中分离获得能够介导metal-AOM的微生物。对海洋沉积物中metal-AOM的研究大多聚焦于热液或冷泉等海洋特殊生境,一系列研究表明地质流体在这些海底化能自养生态系统的维持和演化方面起到了重要作用,并深刻影响全球地球化学循环,因此,该科学问题研究吸引了越来越多的注意力。本文讨论了可能参与海洋沉积物中metal-AOM的微生物类群及其地球化学证据,并在前人工作基础上,以冲绳海槽冷泉-热液共生区为例,提出一种新的metal-AOM作用机制。认为在全球冷泉-热液系统相互作用地区的调查有助于更好地探讨metal-AOM的发生机制及微生物在深海生境中分布的连通性问题。

A large fraction of methane is consumed by anaerobic oxidation(AOM) in marine sediments. Previous researches suggested that AOM is coupled to the reduction of sulfate, nitrate and nitrite, which may effectively reduce methane emission into the atmosphere. Recently,metal-dependent AOM(metal-AOM, AOM driven by active metal oxides reduction reaction) was demonstrated to occur in both the sediments in nature and enriched cultures. But the elusive microorganisms mediating metal-AOM process have not yet been isolated from natural marine environments, and most researches on metal-AOM in marine sediments focus on special marine habitats such as hydrothermal vents or cold seeps. However, a series of investigation shows that geological fluids play an important role in the maintenance and evolution of these submarine chemolithoautotrophy ecosystems, and profoundly affect the global geochemical cycle. Therefore, the research on this scientific problem has attracted more and more attention from marine scientists. In this review, the potential microbial communities and geochemical evidence of metal-AOM in marine sediments are summarized. On the basis of literature researches, taking the cold seeps and hydrothermal vents coexisted region, the Okinawa Trough, as an example, a new metal-AOM mechanism is proposed. The investigation in the global cold seeps and hydrothermal vents system interaction areas could be beneficial to better discuss the mechanism of metal-AOM and the connectivity of microbial distribution in deep-sea habitats.