Spirochaeta smaragdinae Magot et al. 1998 belongs to the family Spirochaetaceae. The species is Gram-negative, motile, obligately halophilic and strictly anaerobic and is of interest because it is able to ferment numerous polysaccharides. S. smaragdinae is the only species of the family Spirochaetaceae known to reduce thiosulfate or element sulfur to sulfide. This is the first complete genome sequence in the family Spirochaetaceae. The 4,653,970 bp long genome with its 4,363 protein-coding and 57 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.