Accretionary prisms are thick masses of sedimentary material scraped from the oceanic crust and piled up at convergent plate boundaries found across large regions of the world. Large amounts of anoxic groundwater and natural gas, mainly methane (CH4), are contained in deep aquifers associated with these accretionary prisms. To identify the subsurface environments and potential for CH4 production by the microbial communities in deep aquifers, we performed chemical and microbiological assays on groundwater and natural gas derived from deep aquifers associated with an accretionary prism and its overlying sedimentary layers. Physicochemical analyses of groundwater and natural gas suggested wide variations in the features of the six deep aquifers tested. On the other hand, a stable carbon isotope analysis of dissolved inorganic carbon in the groundwater and CH4 in the natural gas showed that the deep aquifers contained CH4 of biogenic or mixed biogenic and thermogenic origins. Live/dead staining of microbial cells contained in the groundwater revealed that the cell density of live microbial cells was in the order of 104 to 106 cells mL–1, and cell viability ranged between 7.5 and 38.9%. A DNA analysis and anoxic culture of microorganisms in the groundwater suggested a high potential for CH4 production by a syntrophic consortium of hydrogen (H2)-producing fermentative bacteria and H2-utilizing methanogenic archaea. These results suggest that the biodegradation of organic matter in ancient sediments contributes to CH4 production in the deep aquifers associated with this accretionary prism as well as its overlying sedimentary layers.

中文翻译：

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与增生棱柱及其上覆沉积层相关的不同深层含水层中同养微生物群落生产CH ₄的潜力

增生棱柱是从大洋地壳刮下的厚厚的沉积物质，堆积在世界大部分地区的会聚板块边界上。与这些增生棱柱相关的深层含水层中含有大量缺氧地下水和天然气，主要是甲烷 (CH4)。为了确定深层含水层中微生物群落产生 CH4 的地下环境和潜力，我们对源自与增生棱柱及其上覆沉积层相关的深层含水层的地下水和天然气进行了化学和微生物分析。地下水和天然气的物理化学分析表明，所测试的六个深层含水层的特征存在很大差异。另一方面，对地下水中溶解的无机碳和天然气中的 CH4 的稳定碳同位素分析表明，深层含水层含有生物源或混合生物源和热源的 CH4。地下水中微生物细胞的活/死染色显示，活微生物细胞的细胞密度在104-106个细胞mL-1的数量级，细胞活力在7.5-38.9%之间。地下水中微生物的 DNA 分析和缺氧培养表明，产氢 (H2) 发酵细菌和利用 H2 的产甲烷古菌的同养联合体生产 CH4 的潜力很大。