Spirochaeta smaragdinae sp. nov. : a new mesophilic strictly anaerobic spirochete from an oil field

An obligately anaerobic spirochete designated strain SEBR 4228(T) (T = type strain) was isolated from an oil field of Congo, Central Africa. The strain grew optimally with a sodium chloride concentration of 5% (sodium chloride concentration growth range 1.0-10%) at 37°C (growth temperature range 20-40°C) and pH of 7.0-7.2 (pH growth range pH 5.5-8.0). Strain SEBR 4228(T) grew on carbohydrates (glucose, fructose, ribose, D-xylose, galactose, mannitol and mannose), glycerol, fumarate, peptides and yeast extract. Yeast extract was required for growth and could not be replaced by vitamins. It reduced thiosulfate and sulfur, to H2S. Glucose was oxidised to lactate, acetate, CO2 and H2S in the presence of thiosulfate but in its absence lactate, ethanol, CO2 and H2 were produced. Fumarate was fermented to acetate and succinate. The G+C content of strain SEBR 4228(T) was 50%. Strain SEBR 4228(T) was spiral shaped measuring 5-30 by 0.3-0.5 micrometers and was motile with a corkscrew-like motion. Electron microscopy revealed the presence of periplasmic flagella in a 1-2-1 arrangement. Strain SEBR 4228(T) possessed features typical of the members of the genus #Spirochaeta$. 16S rRNA sequence analysis revealed that it was closely related to #Spirochaeta bajacaliforniensis$ (similarity 98.6%). The lack of DNA homology with #S. bajacaliforniensis$ (38%), together with other phenotypic differences, indicated that strain SEBR 4228(T) is a new species, which we have designated #Spirochaeta smaragdinae$. The type strain is SEBR 4228(T) (= DSM 11293). (Résumé d'auteur