Evolution of acetoclastic methanogenesis in Methanosarcina via horizontal gene transfer from cellulolytic Clostridia

Phylogenetic analysis confirmed that two genes required for acetoclastic methanogenesis, ackA and pta, were horizontally transferred to the ancestor of Medianosarcina from a derived cellulolytic organism in the class Clostridia. This event likely occurred within the last 475 million years, causing profound changes in planetary methane biogeochemistry.