Petrotoga halophila sp nov., a thermophilic, moderately halophilic, fermentative bacterium isolated from an offshore oil well in Congo

A novel thermophilic, moderately halophilic, rod-shaped bacterium, strain MET-B-T with a sheath-like outer structure (toga) was isolated from an offshore oil-producing well in Congo, West Africa. Strain MET-B-T was a Gram-negative bacterium with the ability to reduce elemental sulfur, but not sulfate, thiosulfate or sulfite into sulfide. The optimum growth conditions were 60 degrees C, pH 6.7-7.2 and 4-6% NaCl. The DNA G + C content was 34.6 mol%. Strain MET-B T was phylogenetically related to members of the genus Petrotoga; Petrotoga miotherma, Petrotoga olearia and Petrotoga mexicana were the closest relatives, with type strains exhibiting more than 99% identity in an analysis of small-subunit rRNA gene sequences. The values for DNA-DNA relatedness between the type strains of these three species and strain MET-B T were less than 42%. As MET-B-T was found to be genetically and physiologically different from other species of the genus Petrotoga, this strain is proposed as representing a novel species, for which the name Petrotoga halophila sp. nov. is proposed. The type strain is MET-B-T (= DSM 16923(T) = CCUG 50214(T)).