Phylogenetic tree of the members of the genus Methanobrevibacter based on the 16S rRNA gene. The tree was generated using CLUSTAL W program  for sequence alignment (786 bp) and by the neighbor joining method using Kimura 2 parameter distances in MEGA 2.1 software. Only positions 286–1120 (E. coli numbering) were considered with Msp. stadtmanae as the outgroup. Numbers at nodes indicate percent bootstrap values above 50 (1000 replicates). Bar indicates Jukes-Cantor evolutionary distance. Bold letters indicate isolated strains whereas normal font indicates clones.