The 16S rRNA gene-based phylogeny (NJ and ML analyses) also revealed that strain RMAST is most closely related to members of the genus Methanothermobacter and that the 16S rRNA gene sequence similarities between strain RMAST and the genus Methanothermobacter are higher (95.1–95.7 %) than with the genus Methanobacterium (91.3–93.8 %).