A new moderately halophilic sulfate-reducing bacterium (strain H₁(T) ) was enriched and isolated from a wastewater digestor in Tunisia. Cells were curved, motile rods (2-3 x 0.5 μm). Strain H₁(T) grew at temperatures between 22 and 43°C (optimum 35°C), and at pH between 5.0 and 9.2 (optimum 7.3-7.5). Strain H₁(T) required salt for growth (1-45 g of NaCl/l), with an optimum at 20-30 g/l. Sulfate, sulfite, thiosulfate, and elemental sulfur were used as terminal electron acceptors but not nitrate and nitrite. Strain H₁(T) utilized lactate, pyruvate, succinate, fumarate, ethanol, and hydrogen (in the presence of acetate and CO₂) as electron donors in the presence of sulfate as electron acceptor. The main end-products from lactate oxidation were acetate with H₂ and CO₂. The G + C content of the genomic DNA was 55%. The predominant fatty acids of strain H₁(T) were C(15:0) iso (38.8%), C(16:0) (19%), and C(14:0) iso 3OH (12.2%), and menaquinone MK-6 was the major respiratory quinone. Phylogenetic analysis of the small-subunit (SSU) ribosomal RNA (rRNA) gene sequence indicated that strain H₁(T) was affiliated to the genus Desulfovibrio. On the basis of SSU rRNA gene sequence comparisons and physiological characteristics, strain H₁(T) is proposed to be assigned to a novel species of sulfate reducers of the genus Desulfovibrio, Desulfovibrio legallis sp. nov. (= DSM 19129(T) = CCUG 54389(T)).
Two novel sulfate-reducing bacterial strains, designated E-2 T and IMP-2, were isolated from geographically distinct locations. Strain E-2 T was recovered from marine sediments near Sfax (Tunisia), whereas strain IMP-2 originated from oilfield production fluids in the Gulf of Mexico. Cells were Gram-negative, non-sporulated, motile, vibrio-shaped or sigmoid. They were strictly anaerobic, mesophilic and moderately halophilic. Sulfate, sulfite, thiosulfate and elemental sulfur served as electron acceptors, but not nitrate or nitrite. H 2 (with acetate as carbon source), formate, fumarate, lactate, malate, pyruvate, succinate and fructose were used as electron donors in the presence of sulfate as terminal electron acceptor. Lactate was oxidized incompletely to acetate. Fumarate and pyruvate were fermented. Desulfoviridin and c-type cytochromes were present. 16S rRNA gene sequence analysis of the two strains showed that they were phylogenetically similar (99.0 % similarity) and belonged to the genus Desulfovibrio, with Desulfovibrio indonesiensis and Desulfovibrio gabonensis as their closest phylogenetic relatives. The G+C content of the DNA was respectively 60.4 and 62.7 mol% for strains E-2 T and IMP-2.DNA-DNA hybridization experiments revealed that the novel strains had a high genomic relatedness, suggesting that they belong to the same species. We therefore propose that the two isolates be affiliated to a novel species of the genus Desulfovibrio, Desulfovibrio marinus sp. nov. The type strain is strain E-2 T (5DSM 18311 T 5JCM 14040 T ).
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