Very interestingly, the McrA phylogeny (Fig.2b) revealed that, despite the fact that strain RMAST and Methanothermobacter crinale Tm2T are closely related to Methanothermobacter thermautotrophicus DHT on the basis of 16S rRNA gene sequences (Fig. 2a), they were more related to members of the genus Methanobacterium than to Methanothermobacter.