Methane gas is the second most prevalent greenhouse gas and an abundant source of energy in the United States. Methane is both produced and consumed in marine sediments through anaerobic methanogenesis. Methanogenic archaea primarily use one-carbon substrates such as CO2, acetate, or methanol for growth and methanogenesis through CO2 reduction, aceticlastic, or methylotrophic pathways, respectively. The key step in the methanogenesis pathway, reducing methyl-coenzyme M (CH3-S-CoM) and coenzyme B (HS-CoB) to methane, is catalyzed by Methylcoenzyme M reductase (MCR). This reaction, which leads to the formation of a heterodisulfide substrate (CoM-S-SCoB), is exergonic. Therefore, for reverse methanogenesis to occur, the methane oxidation reaction needs to be coupled with an endergonic reaction that provides a thermodynamically favorable situation.
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