Microbial methane production (methanogenesis) is responsible for more than half of the annual emission of this major greenhouse gas to the atmosphere. Though the stable isotopic composition of methane is often used to characterize its sources and sinks, strictly empirical descriptions of the isotopic signature of methanogenesis currently limit such attempts. We developed a biochemical-isotopic model of methanogenesis by CO₂ reduction, which predicts carbon and hydrogen isotopic fractionations, and clumped isotopologue distributions, as functions of the cell’s environment. We mechanistically explain multiple-isotopic patterns in laboratory and natural settings and show that such patterns constrain the in-situ energetics of methanogenesis. Combining our model with environmental data, we infer that in almost all marine environments and gas deposits, energy-limited methanogenesis operates close to chemical and isotopic equilibrium.

中文翻译：

---

控制微生物甲烷的同位素组成

微生物甲烷的产生（产甲烷作用）占每年向大气排放的这种主要温室气体的一半以上。尽管甲烷的稳定同位素组成通常用于表征其来源和汇，但目前对甲烷生成同位素特征的严格经验描述限制了这种尝试。_{我们开发了 CO 2}产甲烷的生化同位素模型还原，它预测碳和氢的同位素分馏，以及聚集的同位素分布，作为细胞环境的函数。我们机械地解释了实验室和自然环境中的多同位素模式，并表明这种模式限制了产甲烷的原位能量学。将我们的模型与环境数据相结合，我们推断在几乎所有海洋环境和气藏中，能量受限的产甲烷作用接近化学和同位素平衡。