General Information: Methanobrevibacter smithii ATCC 35061 (DSM 861) (strain PS) was isolated from a sewage digester in Gainesville, Florida, USA. Sewage digester isolate. Human gut methanogen. Methanobrevibacter smithii can be isolated from anoxic environments such as anaerobic digesters, anaerobic soil and sediment, and the gastrointestinal tracts of humans, ruminants and other animals. This organism is the dominant archaeal symbiont found in the human gut.