Origin of hydrogen in methane produced by Methanobacterium thermoautotrophicum

Abstract
The production of deuterated methane by M. thermoautotrophicum in H2O-D2O mixtures was examined by high-resolution mass spectrometry. The hydrogen in the methane arose solely from water and not from H2 gas. H2 gas served only as an electron source in methanogenesis. A whole-cell product isotope discrimination of 1.5 favoring H2 over deuterium was observed in methane production in 81 atom% deuterated water. The distribution of deuterated methane species is described by a simple model of the overall reaction.