Sulfurovum riftiae sp. nov., a mesophilic, thiosulfate-oxidizing, nitrate-reducing chemolithoautotrophic epsilonproteobacterium isolated from the tube of the deep-sea hydrothermal vent polychaete Riftia pachyptila

An anaerobic, nitrate-reducing, sulfur- and thiosulfate-oxidizing bacterium, designated strain 1812E(T), was isolated from the vent polychaete Riftia pachyptila, which was collected from a deep-sea hydrothermal vent on the East Pacific Rise. Cells were Gram-stain-negative rods, measuring approximately 1.05 +/- 0.11 mu m by 0.40 +/- 0.05 mu m. Strain 1812E(T) grew at 25 - - 45 degrees C (optimum 35 degrees C), with 1.5-4.0% (w/v) NaCI (optimum 3.0%) and at pH 5.0-8.0 (optimum pH 6.0). The generation time under optimal conditions was 3 h. Strain 1812E(T) was an anaerobic chemolithotroph that grew with either sulfur or thiosulfate as the energy source and carbon dioxide as the sole carbon source. Nitrate was used as a sole terminal electron acceptor. The predominant fatty acids were C-16:1 omega 7c(1) C-18:1 omega 7c and C-16:0. The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The major respiratory quinone was menaquinone MK-6 and the G+C content of the genomic DNA was 47.4 mol%. Phylogenetic analysis of the 16S rRNA gene of strain 1812E(T) showed that the isolate belonged to the Epsilon proteobacteria, and its closest relatives were Sulfurovum lithotrophicum 42BK(T) and Sulfurovum aggregans Monchim 33(T) (98.3 and 95.7% sequence similarity, respectively). DNA DNA relatedness between strain 1812E(T) and the type strain of S. lithotrophicum was 29.7%, demonstrating that the two strains are not members of the same species. Based on the phylogenetic, molecular, chemotaxonomic and physiological evidence, strain 1812E(T) represents a novel species within the genus Sulfurovum, for which the name Sulfurovum riftiae sp. nov. is proposed. The type strain is 1812E(T) (=DSM 101780(T)=JCM 30810(T))