Regular hulls ± 0.7 to 1.5 microns in diameter. Presence of non-cellular appendages of 2.5 microns and sulfur inclusions. During growth, cells are often connected by two by a thin filament non-uniform division by constriction. In rich environment, the appearance of giant forms of 10 microns in diameter. Occasional presence of rod-shaped protrusions. The ultrastructure shows dense parts of the cytoplasm attached to the cell membrane. Anaerobic, heterotrophic growth on peptides, casein, or lactotryptone yeast extract and glucose for the same species, sulfo-reduction. Optimum temperature 87 ° C between pH 4 and 7. Some species have a mucus envelope, others lophotriche polar flagellation. DNA contains 51 mol% G+ C. Five species,Desulfurococcus mucosus .
