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 1 Experimental and organismal information examined in this study

Culture type	T (°C)	Head space H₂ (Pa)	CH₄ substrate	Organism information
Culture type	T (°C)	Head space H₂ (Pa)	CH₄ substrate	Syntrophic bacteria	Methanogen
Thermophilic coculture	55	<6.0 × 10¹	Butyrate	Syntrophothermus lipocalidus (DSMZ 12681)	Methanothermobacter thermautotrophicus strain ΔH (JCM10044)
Mesophilic coculture^a	25	<1.0 × 10¹	Butyrate	Syntrophomonas sp.	Methanobacterium sp. strain MO-MB1
Thermophilic pure culture	60	<2.1 × 10⁵	H₂/CO₂	−	Methanothermococcus okinawensis strain IH1 (JCM11175)
Mesophilic pure culture	30	<2.2 × 10⁵	H₂/CO₂	−	Methanobacterium sp. strain MO-MB1

^aThe mesophilic coculture included a contaminant bacterium, Geosporobacter sp. (Saito et al. 2014)