Methanosphaera stadtmanae DSM 3091

Methanosphaera stadtmanae, the first human archaeal commensal whose genome has been sequenced, thrives in the human intestine, where methanol is a product of pectin degradation by Bacteroides species and other anaerobic bacteria. This human intestinal inhabitant can generate methane only by reduction of methanol with H2 and is dependent on acetate as a carbon source. It has the most restricted energy metabolism of all methanogenic archaea. The genome lacks 37 CDS present in the genomes of all other methanogens. Among these are the CDS for synthesis of molybdopterin (which is required for the enzyme catalyzing the first step of methanogenesis from CO2 + H2) and for synthesis of the CO dehydrogenase/acetyl-coenzyme A synthase complex, which explains why M. stadtmanae cannot reduce CO2 to methane or oxidize methanol to CO2 and why this archaeon is dependent on acetate for biosynthesis of cell components. (HAMAP: METST)