The complete genome sequence of the rumen methanogen Methanobacterium formicicum BRM9

Methanobacterium formicicum BRM₉ was isolated from the rumen of a New Zealand Friesan cow grazing a ryegrass/clover pasture, and its genome has been sequenced to provide information on the phylogenetic diversity of rumen methanogens with a view to developing technologies for methane mitigation. The 2.45 Mb BRM₉ chromosome has an average G + C content of 41%, and encodes 2,352 protein-coding genes. The genes involved in methanogenesis are comparable to those found in other members of the Methanobacteriaceae with the exception that there is no [Fe]-hydrogenase dehydrogenase (Hmd) which links the methenyl-H4MPT reduction directly with the oxidation of H2. Compared to the rumen Methanobrevibacter strains, BRM₉ has a much larger complement of genes involved in determining oxidative stress response, signal transduction and nitrogen fixation. BRM₉ also has genes for the biosynthesis of the compatible solute ectoine that has not been reported to be produced by methanogens. The BRM₉ genome has a prophage and two CRISPR repeat regions. Comparison to the genomes of other Methanobacterium strains shows a core genome of ~1,350 coding sequences and 190 strain-specific genes in BRM₉, most of which are hypothetical proteins or prophage related.