Petrotoga mobilis sp. nov., from a North Sea oil-production well

Rod-shaped, thermophilic bacteria with a sheath-like outer structure ('toga') were isolated from hot oilfield water of a North Sea oil reservoir. One of the isolates, designated SJ95(T), is an obligately anaerobic, sheathed, Gram-negative, fermentative bacterium capable of reducing elemental sulfur to hydrogen sulfide and tolerating high salt concentrations. The optimum growth conditions for this isolate are 58-60 degrees C and ph 6.5-7.0 with 3-4% NaCl and 0.7% MgSO4. 7H(2)O in the medium. Vitamins are required for growth. Growth is stimulated by yeast extract. Cells of strain SJ95(T) vary in sire from 1-2 to 40-50 mu m in length and are motile with a subpolar flagellation. Cells grown on xylan have xylanase activity, presumably associated with the toga, and glucose isomerase activity was detected in xylose-grown cells. The DNA G+C content is 31 and 34 mol%, determined by the thermal denaturation and HPLC methods, respectively. Phylogenetically, strain SJ95(T) is most closely related to Petrotoga miotherma with a 97.7% similarity level between their 16S rDNA sequences. The DNA-DNA reassociation value between the two DNAs was 35.6%. On the basis of differences in genotypic, phenotypic and immunological characteristics, strain SJ95(T)(= DSM 10674(T)) is proposed as the type strain of a new species, Petrotoga mobilis. It can be readily distinguished from P.miotherma by its motility.