Hydrogen and carbon isotope systematics in hydrogenotrophic methanogenesis under H2-limited and H2-enriched conditions: implications for the origin of methane and its isotopic diagnosis

Progress in Earth and Planetary Science

Table 2 Initial stable hydrogen isotopic conditions for the hydrogenotrophic methanogenesis experiments

Batches	Isotope labeling		Initial value		\( {\updelta}^{\mathrm{eq}}{\mathrm{D}}_{{\mathrm{H}}_2\hbox{--} {\mathrm{H}}_2\mathrm{O}} \)
Batches	D₂O	DH	\( {\updelta \mathrm{D}}_{{\mathrm{H}}_2\mathrm{O}} \)	\( {\updelta \mathrm{D}}_{{\mathrm{H}}_2} \)
Thermophilic coculture experimental set (TC, at 55 °C)
A1	−	−	−58	−	−
A2	−	−	−62	−	−
A3	+	−	+1624	−	−
A4	+	−	+1639	−	−
A5	++	−	+3771	−	−
A6	++	−	+3787	−	−
Mesophilic coculture experimental set (MC, at 25 °C)
B1	−	−	−62	−	−
B2	−	−	−58	−	−
B3	+	−	+1406	−	−
B4	+	−	+1413	−	−
B5	++	−	+3662	−	−
B6	++	−	+3286	−	−
Thermophilic pure culture experimental set (TP, at 60 °C)
C1	−	−	−59	−358	DH-rich
C2	−	+	−53	+330	DH-rich
C3	+	−	+1097	−287	Equilibrated
C4	+	++	+1210	+1886	DH-rich
C5	++	−	+2574	−350	D₂O-rich
C6	++	+	+2317	+70	Equilibrated
Mesophilic pure culture experimental set (MP, at 30 °C)
D1	−	−	−54	−344	DH-rich
D2	+	+	+1427	+145	DH-rich
D3	+	+	+1424	+22	DH-rich
D4	+	−	+1369	−350	Equilibrated
D5	+	−	+1382	−349	Equilibrated
D6	++	−	+3096	−351	D₂O-rich
D7	++	+	+3142	+85	Equilibrated