GENERAL GEOLOGY

Detailed explanation-1: -Three major pathways of methanogenesis are known (8, 9): hydrogenotrophic, methylotrophic, and acetoclastic (Fig.

Detailed explanation-2: -Methanogenesis is an anaerobic respiration that generates methane as the final product of metabolism. In aerobic respiration, organic matter such as glucose is oxidized to CO2, and O2 is reduced to H2O. In contrast, during hydrogenotrophic methanogenesis, H2 is oxidized to H+, and CO2 is reduced to CH4.

Detailed explanation-3: -Three main methanogenesis pathways (hydrogenotrophic, aceticlastic, and methylotrophic) have been described that share the core pathway of methanogenesis yet also differ in many aspects of their biochemistry and physiology. The largest phylogenetic diversity is found within the hydrogenotrophic methanogens.

Detailed explanation-4: -Five Orders of methanogens have been identified: Methanopyrales, Methanococcales, Methanobacteriales, Methanomicrobiales and Methanosarcinales [2].