The deduced amino acid sequences of mcrA of strain
RMAST using the MCRf/MCRr and ME1/ME2 primer
pairs were 157 and 240 amino acids long, respectively. The
McrA sequence of strain RMAST exhibited high similarities
with those of Methanothermobacter crinale Tm2T and
Methanobacterium aarhusense H2-LRT (96.7 and 90.1 %,
respectively). 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. The reason for the discrepancy
between the 16S rRNA gene and McrA phylogenies is not
clear, but the physiological and biochemical features, as
shown below, support the placement of strain RMAST in
the genus Methanothermobacter.