Short rods or shells lanceolate (0.7 x 0.8 to 1.8 microns), non-motile, often in pairs or chains and resembling streptococci. Gram positive. Yellow colony convex and regular. Uses H2 + CO2 and formate. Mesophilic often demanding growth factors (rumen). DNA contains from 27 to 32 mol% G+ C The genus comprises 14 species, including the type species Methanobrevibacter ruminantium who lives in the rumen of cattle. Methanobrevibacter arboriphilus was isolated from living trees, it does not use formate.
