Phylogeny of Methanomassiliicoccales sequences and highly abundant Methanomassiliicoccales OTUs. Representative sequences of highly abundant OTUs (AS99ML1, AS99ML2, and AS99ML3) were aligned to the ARB database, version 111, using SINA-aligner (26). Fifty-seven sequences of group10, group11, and group12 and of isolates and enrichment cultures were selected in RIM-DB (14). Phylogenetic analysis was performed on the V6-to-V8 region of the 16S rRNA gene of the aligned OTUs and selected database sequences. The tree was resampled 500 times, and only bootstrap values of ≥70% are shown. The dendrogram was rooted with five Methanopyrus sequences. The scale bar indicates 0.10 inferred nucleotide substitutions per position. Mmc., Methanomassiliicoccus; Mmp., Methanomethylophilus; Mg., Methanogranum.