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.