Methanothrix

Methanothrix is a genus of methanogenic archaea within the phylum Methanobacteriota. Methanothrix cells were first isolated from a mesophilic sewage digester but have since been found in many anaerobic and aerobic environments. Methanothrix were originally understood to be obligate anaerobes that can survive exposure to high concentrations of oxygen, but recent studies have shown at least one Candidatus operational taxonomic unit proposed to be in the Methanothrix genus not only survives but remains active in oxic soils. This proposed species, Ca. Methanothrix paradoxum, is frequently found in methane-releasing ecosystems and is the dominant methanogen in oxic soils.

Methanothrix are non-motile rod-shaped cells which connect together to form long filaments. These filaments are enclosed in a proteinaceous sheath. Methanothrix species, like their close relative Methanosarcina barkeri, have membranes entirely composed of diphytanylglycerol diethers.