SPIROCHAETA SMARAGDINAE SP. NOV., A NEW MESOPHILIC STRICTLY ANAEROBICSPIROCHETE 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 degrees C ( growth temperature range 20-40 degrees 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), glycer ol, fumarate, peptides and yeast extract. Yeast extract was required f or growth and could not be replaced by vitamins. It reduced thiosulfat e and sulfur, to H2S. Glucose was oxidised to lactate, acetate, CO2 an d H2S in the presence of thiosulfate but in its absence lactate, ethan ol, CO2 and H-2 were produced. Fumarate was fermented to acetate and s uccinate. 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 mu m and was motil e with a corkscrew-like motion. Electron microscopy revealed the prese nce 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 Spi rochaeta bajacaliforniensis (similarity 98.6%). The lack of DNA homolo gy with S. bajacaliforniensis (38%), together with other phenotypic di fferences, indicated that strain SEBR 4228(T) isa new species, which w e have designated Spirochaeta smaragdinae. The type strain is SEBR 422 8(T) (= DSM 11293).