Desulfurococcus mucosus Zillig and Stetter 1983 is the type species of the genus Desulfuro-coccus, which belongs to the crenarchaeal family Desulfurococcaceae. The species is of in-terest because of its position in the tree of life, its ability for sulfur respiration, and several bio-technologically relevant thermostable and thermoactive extracellular enzymes. This is the third completed genome sequence of a member of the genus Desulfurococcus and already the 8 ^th sequence from a member the family Desulfurococcaceae. The 1,314,639 bp long ge-nome with its 1,371 protein-coding and 50 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.