Effect of temperature on methanogens metabolic pathway and structures of predominant bacteria

Methanogens are strictly anaerobic archaea, which not only take part in the methanogenesis procedure but also limit this process. Temperature plays a key role in the anaerobic fermentation. Temperature could not only directly alter the community structure and function of methanogenic archaea,but also affect the supply of substrates for methanogens,which in turn indirectly regulates the pathways of methanogenic archaea.There are three pathway for methanogenesis, and they are started from acetic acid, H2/CO2 and C-1 compound respetively. Acetoclastic methanogenesis accounts for about two-thirds of the total methane production globally, while hydrogenotrophic methanogenesis accounts for about one third. Methanol- and methyl amine-derived methanogensis is restricted in ocean and saline water. Acetoclastic methanogenesis is the predominant methanogenesis at a low temperature, and methane is produced by acetoclastic and hydrogenotrophic methanogenesis at a medium temperature, while methane is exclusively produced by hydrogenotrophic methanogenesis at a high or ultra-high temperature.