Fractionation of the methane isotopologues 13CH4, 12CH3D, and 13CH3D during aerobic oxidation of methane by Methylococcus capsulatus (Bath) Journal Article uri icon

DCO ID 11121/3222-2054-8350-1195-CC

is Contribution to the DCO

  • YES

year of publication

  • 2016


  • Aerobic oxidation of methane plays a major role in reducing the amount of methane emitted to the atmosphere from freshwater and marine settings. We cultured an aerobic methanotroph, Methylococcus capsulatus  (Bath) at 30 and 37 °C, and determined the relative abundance of 12 CH413 CH412 CH3 D, and 13 CH3 D (a doubly-substituted, or “clumped” isotopologue of methane) to characterize the clumped isotopologue effect associated with aerobic methane oxidation. In batch culture, the residual methane became enriched in 13 C and D relative to starting methane, with D/H fractionation a factor of 9.14 (D ε/13 ε) larger than that of 13 C/12 C. As oxidation progressed, the Δ13 CH3 D value (a measure of the excess in abundance of 13 CH3 D relative to a random distribution of isotopes among isotopologues) of residual methane decreased. The isotopologue fractionation factor for 13 CH3 D/12 CH4  was found to closely approximate the product of the measured fractionation factors for 13 CH4 /12 CH4  and 12 CH3 D/12 CH4  (i.e., 13 C/12 C and D/H). The results give insight into enzymatic reversibility in the aerobic methane oxidation pathway. Based on the experimental data, a mathematical model was developed to predict isotopologue signatures expected for methane in the environment that has been partially-oxidized by aerobic methanotrophy. Measurement of methane clumped isotopologue abundances can be used to distinguish between aerobic methane oxidation and alternative methane-cycling processes.


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