Stable carbon isotope fractionation between substrates and products of Methanosarcina barkeri

There were large differences in the δ13C among the M. barkeri lipids produced within each experiment, with the notable exception of growth on acetate. The 13C content of lipids was generally well correlated with that of biomass, with archaeol showing the strongest relationship. The 13C content of individual lipids varied with substrate availability in some cases, but did not show patterns that could be used to identify the growth substrate of methanogens in natural environments.