Desulfovibrio tunisiensis sp. nov., a novel weakly halotolerant, sulfate-reducing bacterium isolated from exhaust water of a Tunisian oil refinery

1 Laboratoire d'Immuno-Microbiologie Environnementale (LIME), Faculté des Sciences de Bizerte, 70021 Zarzouna, Tunisia 2 Laboratoire de Microbiologie et Biotechnologie des Environnements Chauds (LMBEC), IRD-UMR 180-ESIL CP-925, Universités de Provence et de la Méditerranée, 163 Avenue de Luminy, 13288 Marseille cedex 9, France 3 Laboratory of Enzymology at Interfaces and Physiology of Lipolysis, CNRS-UPR 9025-IBSM, 31 Chemin Joseph-Aiguier, 13009 Marseille, France Correspondence Marc Labat labat{at}esil.univmed.fr A novel weakly halotolerant, sulfate-reducing bacterium, designated strain RB22 T , was isolated from exhaust water of a Tunisian oil refinery. Cells of strain RB22 T were Gram-negative, motile, vibrio-shaped or sigmoid and non-spore-forming, and occurred singly or in chains. Strain RB22 T grew between 15 and 45 °C (optimum, 37 °C) and at pH 4.5 to 9 (optimum, pH 7). NaCl was not required for growth, but the strain tolerated high NaCl concentrations (up to 70 g l –1 ) with an optimum of 40 g l –1 . Sulfate, thiosulfate, sulfite and elemental sulfur served as electron acceptors, but not fumarate. Nitrate and nitrite were not reduced. Strain RB22 T utilized lactate, formate, fumarate, succinate, glycerol, H 2 +CO 2 and methanol as substrates. The DNA G+C content was found to be 59.6 mol%. Phylogenetic analysis based on the 16S rRNA gene revealed that the isolate was a member of the genus Desulfovibrio , with no close relatives at the species level (16S rRNA gene sequence similarity of less than 95 %). Strain RB22 T exhibited levels of 16S rRNA gene sequence similarity of 94.6 and 94.12 % to the type strains of the closely related species Desulfovibrio aespoeensis and Desulfovibrio dechloracetivorans , respectively. On the basis of genotypic and phylogenetic characteristics, and significant phenotypic differences, we suggest that strain RB22 T represents a novel species, for which the name Desulfovibrio tunisiensis sp. nov. is proposed. The type strain is RB22 T (=NCIMB 14400 T =JCM 15076 T =DSM 19275 T ). Abbreviations: SRB, sulfate-reducing bacteria The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain RB22 T is EF577029 .