Methanosarcinales

Methanosarcinales is an order of Archaea in the class Methanomicrobia, phylum Methanobacteriota. The order Methanosarcinales contains both methanogenic and methanotrophic lineages, although the latter have so far no pure culture representatives. Methanotrophic lineages of the order Methanosarcinales were initially abbreviated as ANME (anaerobic methanotrophs) to distinguich from aerobic methanotrophic bacteria. Currently, those lineages receive their own names such as Ca. Methanoperedens, Ca. Methanocomedens (ANME-2a), Ca.Methanomarinus (ANME-2b), Ca. Methanogaster (ANME-2c), Ca. Methanovorans (ANME-3). The order contains archaeon with one of the largest genome, Methanosarcina acetivorans C2A, genome size 5,75 Mbp.

The organisms placed within the order can be found in freshwater, saltwater, salt-rich sediments, anaerobic digestors, and animal digestive systems. The order consist of mesophiles or moderately thermophillic, neutrophilic or alkaliphilic species with some able to grow at high salt concentrations (genera Methanohalobium, Methanohalophilus, and Methanosalsum). Most of the species in the order were isolated or detected in marine and freshwater sediments, soil with only a few specialized lineages adapted to the digestive tract of animals - genera Methanimicrococcus, Methanolapillus, and Ca. Methanofrustulum that can be found in termites/cockroaches, millipedes, and ruminants, respectively.