Methanogenesis is the final step in the anaerobic degradation of organic matter. The most important substrates of methanogens are hydrogen plus carbon dioxide and acetate, but also the use of methanol, methylated amines, and aromatic methoxy groups appears to be more widespread than originally thought. Except for most members of the family Methanosarcinaceae, all methylotrophic methanogens require external hydrogen as reductant and therefore compete with hydrogenotrophic methanogens for this common substrate. Since methanogenesis from carbon dioxide consumes four molecules of hydrogen per molecule of methane, whereas methanogenesis from methanol requires only one, methyl-reducing methanogens should have an energetic advantage over hydrogenotrophic methanogens at low hydrogen partial pressures. However, experimental data on their hydrogen threshold is scarce and suffers from relatively high detection limits. Here, we show that the methyl-reducing methanogens Methanosphaera stadtmanae (Methanobacteriales), Methanimicrococcus blatticola (Methanosarcinales), and Methanomassiliicoccus luminyensis (Methanomassiliicoccales) consume hydrogen to partial pressures < 0.1 Pa, which is almost one order of magnitude lower than the thresholds for M. stadtmanae and M. blatticola reported in the only previous study on this topic. We conclude that methylotrophic methanogens should outcompete hydrogenotrophic methanogens for hydrogen and that their activity is limited by the availability of methyl groups.

中文翻译：

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专门还原甲基的产甲烷菌的氢阈值。

甲烷生成是有机物厌氧降解的最后一步。产甲烷菌最重要的底物是氢，二氧化碳和乙酸盐，但甲醇，甲基化胺和芳族甲氧基的使用似乎比最初想像的要广泛。除甲烷菌科的大多数成员外，所有的甲基营养型产甲烷菌都需要外部氢作为还原剂，因此与氢营养型产甲烷菌竞争这种常见的底物。由于二氧化碳的甲烷生成过程每分子甲烷消耗四分子氢，而甲醇的甲烷生成过程只需要一个分子，因此在低氢分压下，甲基还原的甲烷生成物应比氢营养型甲烷生成物具有能量优势。然而，关于它们的氢阈值的实验数据是稀缺的并且具有相对较高的检测限。在这里，我们显示了甲基还原甲烷菌Methanosphaera stadtmanae（Methanobacteriales），Methanimicrococcus blatticola（Methanosarcinales）和发光甲烷甲烷球菌（Methanomassiliicoccales）消耗氢气至分压<0.1 Pa，这比之前关于该主题的唯一研究报道的斯塔德曼科和布拉提菌的阈值低了近一个数量级。我们得出的结论是，对于氢来说，甲基营养型产甲烷菌应该比氢营养型产甲烷菌更胜一筹，并且它们的活性受到甲基可用性的限制。