Unique coenzymes in microbial physiology: which group of microorganisms characteristically uses coenzyme M and coenzyme F420 in their energy metabolism?

Introduction / Context:
Distinct microbial groups use signature cofactors that serve as biochemical fingerprints. In archaeal methanogenesis, unique coenzymes participate in one-carbon transfers and redox steps that culminate in methane formation from substrates such as CO2, acetate, or methylated compounds.

Given Data / Assumptions:

• Two named cofactors: coenzyme M (HS–CoM) and coenzyme F420.
• We must match these cofactors to the appropriate microbial group.
• Consider roles in methane biochemistry.

Concept / Approach:
Methanogens (archaea) use coenzyme M to form methyl–CoM intermediates and to release methane in the terminal step (methyl–CoM reduction). Coenzyme F420 is a deazaflavin cofactor serving as a low-potential electron carrier in methanogenic pathways and related reductive processes.

Step-by-Step Solution:

Verification / Alternative check:
Biochemistry of methanogenic archaea consistently highlights HS–CoM and F420 among hallmark cofactors, distinguishing them from methanotrophs or sulfate reducers.

Why Other Options Are Wrong:

• Sulfate reducers and acetogens use different cofactors (for example, cytochromes, corrinoids) and do not rely on HS–CoM/F420 as defining features.
• Methanotrophs oxidize methane; they are not producers of methane.

Common Pitfalls:
Confusing methanotrophy (oxidation of methane) with methanogenesis (production of methane). The cofactors named belong to the latter.

Final Answer:
Methanogens (methane-producing microbes)