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 reser voir. One of the isolates, designated SJ95<SUP>T</SUP>, is an obligate ly anaerobic, sheathed, Gram-negative, fermentative bacterium capable of reducing elemental sulfur to hydrogen sulfide and tolerating high s alt 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% MgSO<INF>4</IN F>. 7H<INF>2</INF>O in the medium. Vitamins are required for growth. G rowth is stimulated by yeast extract. Cells of strain SJ95<SUP>T</SUP> vary in sire from 1-2 to 40-50 mu m in length and are motile with a s ubpolar flagellation. Cells grown on xylan have xylanase activity, pre sumably associated with the toga, and glucose isomerase activity was d etected 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<SUP>T</SUP><INF></INF> is most closely related to Petrotoga miotherma with a 97.7% similarity level between t heir 16S rDNA sequences. The DNA-DNA reassociation value between the t wo DNAs was 35.6%. On the basis of differences in genotypic, phenotypi c and immunological characteristics, strain SJ95<SUP>T</SUP>(= DSM 106 74<SUP>T</SUP>) is proposed as the type strain of a new species, Petro toga mobilis. It can be readily distinguished from P.miotherma by its motility.