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MethanosarcinaRANK: GenusTAXONOMY: cellular organisms -> Archaea -> Euryarchaeota -> Methanomicrobia -> Methanosarcinales -> Methanosarcinaceae -> Methanosarcina OVERVIEW: Irregular spheroid bodies (1–3 µm in diameter), occurring alone or typically in aggregates of cells (aggregates up to 1000 µm in diameter). Sometimes occur as large cysts with a common outer wall surrounding individual coccoid cells. Refer to Figures 1, 2, and 3 for typical morphologies. Endospores not formed. Gram stain results are variable. Nonmotile. May contain gas vesicles (Figure 4). Strictly anaerobic. Optimum growth temperatures are 30–40°C for mesophilic species and 50–55°C for thermophiles. Energy metabolism via formation of methane from acetate, methanol, monomethylamine, dimethylamine, trimethylamine, H2/CO2, and CO. Some strains do not use H2/CO2 as the sole energy substrate. May grow very slowly on pyruvate. N2 may be fixed. The mol% G + C of the DNA is: 36–43. Type species: Methanosarcina barkeri |