and Methanothermobacter defluvii ADZT (95.5%), which strongly supports placing strain RMAST in the genus Methanothermobacter. Also, Methanothermobacter crinale Tm2T and Methanobacterium thermaggregans DSM 3266T were found to be closely related to strain RMAST (98.7 and 95.7% sequence similarity, respectively); however, we did not include them for comparative analysis because Methanothermobacter crinale Tm2T was not validly described at the time of writing