Mayumi Daisuke, Tamaki Hideyuki, Kato Souichiro, Igarashi Kensuke, Lalk Ellen, Nishikawa Yasunori, Minagawa Hideki, Sato Tomoyuki, Ono Shuhei, Kamagata Yoichi, Sakata Susumu
Institute for Geo-Resources and Environment, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
Science. 2024 Dec 20;386(6728):1372-1376. doi: 10.1126/science.ado0126. Epub 2024 Dec 19.
Methane, a greenhouse gas and energy source, is commonly studied using stable isotope signals as proxies for its formation processes. In subsurface environments, methane often exhibits equilibrium isotopic signals, but the equilibration process has never been demonstrated in the laboratory. We cocultured a hydrogenotrophic methanogen with an H-producing bacterium under conditions (55°C, 10 megapascals) simulating a methane-bearing subsurface. This resulted in near-complete reversibility of methanogenesis, leading to equilibria for both hydrogen and carbon isotopes. The methanogen not only equilibrated kinetic isotope signals of initially produced methane but also modified the isotope signals of amended thermogenic methane. These findings suggest that hydrogenotrophic methanogenesis can overwrite the isotope signals of subsurface methane, distorting proxies for its origin and formation temperature-insights crucial for natural gas exploration.
甲烷作为一种温室气体和能源，通常利用稳定同位素信号作为其形成过程的替代指标进行研究。在地下环境中，甲烷常常呈现出平衡同位素信号，但该平衡过程从未在实验室中得到证实。我们在模拟含甲烷地下环境的条件（55°C，10兆帕斯卡）下，将一种氢营养型产甲烷菌与一种产氢细菌进行共培养。这导致了甲烷生成几乎完全可逆，从而使氢和碳同位素都达到平衡。该产甲烷菌不仅使最初产生的甲烷的动力学同位素信号达到平衡，还改变了添加的热成因甲烷的同位素信号。这些发现表明，氢营养型甲烷生成可以覆盖地下甲烷的同位素信号，扭曲其来源和形成温度的替代指标——这对天然气勘探至关重要。
