RESUMO
Two moderately halophilic, mesophilic, sulfate-reducing bacteria were isolated from production-water samples from Emeraude Oilfield, Congo. Motile, vibrioid cells of SRL4225T grew optimally at a concentration of 4 % NaCl, at pH 5.8-6.2, with a minimal pH for growth of 5.2, showing that it is a moderately acidophilic bacterium. Cells of SRL6146T were motile, curved or vibrioid, long and thin rods. Optimal growth was obtained at a concentration of 5-6 % NaCl, at pH 6.8-7.2. The nutritional requirements showed that many of the characteristics of these strains overlap with those of known Desulfovibrio species. On the basis of 16S rRNA gene sequence analysis and DNA-DNA hybridization studies, both strains are members of the genus Desulfovibrio. However, they are not closely related to any species of the genus that have validly published names. It is therefore proposed that the two strains are members of two novel species of the genus Desulfovibrio with the names Desulfovibrio bastinii sp. nov. (type strain SRL4225T = DSM 16055T = ATCC BAA-903T) and Desulfovibrio gracilis sp. nov. (type strain SRL6146T = DSM 16080T = ATCC BAA-904T).
