Practice question

Methanogenesis, anaerobic production of methane as catabolic end product, is restricted to Archaea possessing coenzymes methanofuran, tetrahydromethanopterin, and coenzyme M unique to this group and absent in bacteria. Most cultivated methanogens including Methanobacterium, Methanococcus, and Methanosarcina belong phylogenetically to phylum Euryarchaeota which also includes halophiles, thermoplasmatales, and Archaeoglobus sulfate reducers. Crenarchaeota primarily comprises hyperthermophiles lacking methanogenic capacity. Euryarchaeal 16S rRNA clustering and shared methanogenic pathway enzymes define this metabolic coherence, playing crucial role in anaerobic digestion, rumen function, and global carbon cycle regulation.