Which type of microorganisms are referred to as methanogens?

Methanogens are a specific group of microorganisms known for their crucial role in anaerobic environments where they produce methane as a metabolic byproduct. These microorganisms belong to a diverse group called Archaea, and they thrive in environments such as wetlands, the guts of ruminants, and anaerobic digesters used in wastewater treatment processes.

The defining characteristic of methanogens is their ability to utilize substrates like carbon dioxide, hydrogen, acetate, and other organic compounds to generate methane. This metabolic process is vital in natural ecosystems and engineered systems alike, as it helps to recycle organic material and contributes to biogas production, which can be harnessed as a renewable energy source.

In contrast, the other options refer to different types of microorganisms with distinct functions. Acid producers are typically involved in fermentation processes, nitrogen fixers convert atmospheric nitrogen into forms usable by plants, and cellulose degraders specialize in breaking down plant materials in environments suitable for their growth. Hence, the uniqueness of methanogens as methane formers highlights their important role in anaerobic digestion and energy recovery processes.