Methanogens are a unique group of prokaryotic microorganisms that produce methane gas as a metabolic byproduct in anaerobic (oxygen-free) conditions. They are classified under the domain Archaea and specifically belong to the group known as Archaebacteria. These organisms are often extremophiles, capable of living in harsh environments such as marshy areas, hot springs, and the digestive tracts of ruminant animals like cows. Their cell walls differ from true bacteria as they lack peptidoglycan and instead contain pseudomurein.

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