methanosarcinaceae methanosarcinaceae in taxonomy, the methanosarcinaceae are a family of the methanosarcinales. methanosarcinaceae methanosarcina barkeri fusaro scientific classification domain: archaea kingdom: euryarchaeota phylum: euryarchaeota class: methanomicrobia order: methanosarcinales family: methanosarcinaceaebalch and wolfe 1981 genera halomethanococcus yu & kawamura 1988 methanimicrococcus methanococcoides methanohalobium methanohalophilus methanolobus methanomethylovorans methanosalsum methanosarcina "ca. methanovorans" chadwick et al. 2022 phylogeny the currently accepted taxonomy is based on the list of prokaryotic names with standing in nomenclature (lpsn) and national center for biotechnology information (ncbi) 16s rrna-based ltp_01_2022 53 marker proteins based gtdb 07-rs207 methanohalobium zhilina & zavarzin 1988 methanosalsum boone and baker 2002 methanococcoides sowers and ferry 1985 methanohalophilus paterek and smith 1988 methanomethylovorans lomans et al. 2004 methanolobus könig and stetter 1983 methanimicrococcus sprenger et al. 2000 methanosarcina kluyver and van niel 1936 methanimicrococcus methanosarcina methanohalobium methanosalsum methanococcoides methanohalophilus methanomethylovorans methanolobus biochemistry a notable trait of methanosarcinaceae is that they are methanogens that incorporate the unusual amino acid pyrrolysine into their enzymes. the enzyme monomethylamine methyltransferase catalyzes the reaction of monomethylamine to methane. this enzyme includes pyrrolysine. the unusual amino acid is inserted using a unique trna, the anticodon of which is uag. in most organisms, and in most methanosarcinaceae proteins, uag is a stop codon. however in this enzyme, and anywhere else pyrrolysine is incorporated, likely through contextual markers on the mrna, the pyrrolysine-loaded trna is inserted instead of the release factor. they also have a unique aminoacyl-trna synthetase to specifically load this trna with pyrrolysine. this unique adaptation is still the subject of significant study.