Methanobacterium

Methanobacterium is a genus of the Methanobacteria class in the Archaea kingdom, which produce methane as a metabolic byproduct. Despite the name, this genus belongs not to the bacterial domain but the archaeal domain (for instance, they lack peptidoglycan in their cell walls). Methanobacterium are nonmotile and live without oxygen, which is toxic to them, and they only inhabit anoxic environments.

A shared trait by all methanogens is their ability to recycle products. They can use the products of metabolic activities occurring during methanogenesis as substrates for the formation of methane. Methanobacterium species typically thrive in environments with optimal growth temperatures ranging from 28 to 40 °C, and in versatile ecological ranges. They are a part of the scientific world that is still relatively unknown, but methanogens are thought to be some of earth's earliest life forms. They do not create endospores when nutrients are limited. They are ubiquitous in some hot, low-oxygen environments, such as anaerobic digesters, wastewater, and hot springs.