Microbial coal-bed methane is an important economic resource and source of a potent greenhouse gas, but controls on its formation are poorly understood. To test whether the microbial degradability of coal limits microbial methane, we monitored methoxyl group demethylation—a reaction that feeds methanogenesis—in a global sample suite ranging in maturity from wood to bituminous coal. Carbon isotopic compositions of residual methoxyl groups were inconsistent with a thermal reaction, instead implying a substrate-limited biologic process. This suggests that deep biosphere communities participated in transforming plant matter to coal on geologic time scales and that methoxyl abundance influences coal-bed methane yield. Carbon isotopic enrichments resulting from microbial methylotrophy also explain an enigmatic offset in the carbon-13 content of microbial methane from coals and conventional hydrocarbon deposits.

中文翻译：

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甲氧基稳定同位素对煤层气成因和限制的制约

微生物煤层气是重要的经济资源和强效温室气体的来源，但对其形成的控制知之甚少。为了测试煤的微生物降解性是否限制了微生物甲烷，我们在从木材到烟煤的成熟度范围内的全球样本组中监测了甲氧基去甲基化——一种促进产甲烷的反应。残留甲氧基的碳同位素组成与热反应不一致，而是意味着受底物限制的生物过程。这表明深层生物圈群落在地质时间尺度上参与了将植物物质转化为煤的过程，甲氧基丰度影响煤层气产量。