Fractionation of the methane isotopologues 13CH4, 12CH3D, and 13CH3D during aerobic oxidation of methane by Methylococcus capsulatus (Bath). (1st November 2016)

• Record Type: Journal Article
• Authors: Wang, David T.; Welander, Paula V.; Ono, Shuhei
• Is Part Of: Geochimica et cosmochimica acta. Volume 192(2016:Nov. 01)
• Page Start: 186
• Page End: 202
• Publication Date: 2016-11-01
• Subjects: Methane -- Clumped isotopologues -- Aerobic methane oxidation -- Methanotrophic cultures -- Isotopic fractionation; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2016.07.031
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: 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 CH4, 13 CH4, 12 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 Δ 13 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.