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

Abstract

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 H 2S. Glucose was oxidised to lactate, acetate, CO 2 and H 2S in the presence of thiosulfate but in its absence lactate, ethanol, CO 2 and H 2 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 μm 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).