Fig. 3From: Hydrogen and carbon isotope systematics in hydrogenotrophic methanogenesis under H2-limited and H2-enriched conditions: implications for the origin of methane and its isotopic diagnosisRelations between \( {\updelta}^{13}{\mathrm{C}}_{{\mathrm{C}\mathrm{O}}_2} \) and \( {\updelta}^{13}{\mathrm{C}}_{{\mathrm{C}\mathrm{H}}_4} \) values during growth in each of the four experiment sets (a–d). Symbols are the same as those in Fig. 1. The black arrow in each panel shows orders of the values along with the time of growth. Diagonal dashed lines indicate the theoretical isotope fractionation factors between CO2 and CH4 Back to article page