Summary auto-generated
Researchers isolated a novel sulfate-reducing bacterium, designated strain B54T, from a water-oil separation system on a North Sea oil platform. The bacterium was identified as a new species within the genus Desulfobacter and named Desulfobacter vibrioformis. This gram-negative, vibrio-shaped organism grows optimally at 33°C and pH 6.8-7.0 in marine conditions. Unlike most Desulfobacter species, D. vibrioformis requires no vitamins and uniquely uses acetate as its sole carbon source while reducing sulfate, sulfite, and thiosulfate. The organism oxidizes acetate completely to CO2 through an operative citric acid cycle and possesses nitrogen-fixation capability. Phylogenetic analysis using 16S rDNA sequencing showed 98.1% similarity to D. latus, but DNA-DNA hybridization revealed only 40.5% relatedness, supporting classification as a distinct species. The bacterium contains desulforubidin and cytochromes of types b and c, with a DNA G+C content of 47 mol%. Multiple phenotypic, genotypic, immunological, and serological differences distinguish D. vibrioformis from other validly described Desulfobacter species, particularly its distinctive large, curved cell morphology.
Key findings
- A new sulfate-reducing bacterial species, Desulfobacter vibrioformis, was isolated from North Sea oil field water and characterized as a vibrio-shaped, marine, acetate-oxidizing organism with unique metabolic and physiological properties.
- D. vibrioformis differs from related Desulfobacter species by requiring no vitamins, utilizing sulfite and thiosulfate as electron acceptors, and displaying distinctive protein profiles and serological properties.
- 16S rDNA sequence analysis showed 98.1% similarity to D. latus, but DNA-DNA hybridization of only 40.5% confirmed species-level distinction according to accepted taxonomic criteria.
- The organism possesses an operative citric acid cycle for acetate oxidation, nitrogen-fixation capability, and contains desulforubidin and b- and c-type cytochromes with 47 mol% G+C DNA content.
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Abstract
A mesophilic, gram-negative, vibrio-shaped, marine, acetate-oxidizing sulfate reducer (strain B54) was isolated from a water-oil separation system on a North Sea oil platform. The optimum conditions for growth were 33 degrees C, pH 6.8 to 7.0, and concentrations of NaCl and MgCl2.6H2O of at least 1 and 0.3%, respectively. Of various organic acids tested, only acetate was used as an electron and carbon source. The presence of 2-oxoglutarate:dye oxidoreductase suggests acetate oxidation via an operative citric acid cycle. Even though growth of most Desulfobacter strains (including strain B54) did not occur on hydrogen, hydrogenase was detected at low activity. The growth yields were 4.6, 13.1, and 9.6 g of (dry weight) cells per mol of acetate oxidized with sulfate, sulfite, and thiosulfate, respectively, as electron acceptors. Strain B54 was able to fix dinitrogen. Desulforubidin and cytochromes of the c and b types were present. The G+C content of the DNA was 47 mol%. Strain B54 is most closely related to Desulfobacter latus, with a 16S rDNA sequence similarity of 98.1%. The DNA-DNA relatedness between them was 40.5%. On the basis of differences in genotypic, phenotypic, and immunological characteristics, we propose that strain B54 is a member of a new species, D. vibrioformis. It can be easily identified and distinguished from other Desulfobacter species by its large, vibrioshaped cells.