Desulfovibrio marinus sp. nov., a moderately halophilic sulfate-reducing bacterium isolated from marine sediments in Tunisia
O. Ben Dhia Thabet,1,2 M.-L. Fardeau,1 C. Suarez-Nunez,1,3 M. Hamdi,2 ˜ 1 1 1,3 P. Thomas, B. Ollivier and D. Alazard
Correspondence D. Alazarddidier.firstname.lastname@example.org
´ ´ ´ Laboratoire de Microbiologie IRD, UMR 180, Universites de Provence et de la Mediterranee, ESIL, Case 925, 163 Avenue de Luminy, 13288 Marseille cedex 9, France Laboratoire d’Ecologie et de Technologie Microbienne, INSAT, 1080 Tunis, Tunisia
´ ´ ´ Instituto Mexicano del Petroleo, Programa de Biotecnologıa del Petroleo, 07730 Mexico DF, ´ Mexico
Two novelsulfate-reducing bacterial strains, designated E-2T and IMP-2, were isolated from geographically distinct locations. Strain E-2T 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 andmoderately halophilic. Sulfate, sulfite, thiosulfate and elemental sulfur served as electron acceptors, but not nitrate or nitrite. H2 (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-2T andIMP-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-2T (5DSM 18311T 5JCM 14040T).
Sulfate-reducing bacteria (SRB) are widely presentin natural habitats with high sulfate concentrations such as marine environments, where they contribute significantly to organic matter mineralization (Fauque & Ollivier, 2004). They are defined by their ability to use sulfate as a terminal electron acceptor during anaerobic respiration. Phylogenetically, they may be divided into four major groups, based on 16S rRNA gene sequence analysis. Theyinclude the Gram-negative SRB of the Deltaproteobacteria, the Gram-positive spore-forming SRB, the deeply branching thermophilic SRB and the thermophilic archaeal sulfate reducers (Castro et al., 2000; Fauque & Ollivier, 2004; Stackebrandt et al., 1995). The mesophilic members of the Deltaproteobacteria represent the largest group of SRB, now including around 40 genera. Members of the genusAbbreviation: SRB, sulfate-reducing bacteria. The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains E-2T and IMP-2 are respectively DQ365924 and DQ365925.
Desulfovibrio have been isolated frequently from marine environments, including Desulfovibrio acrylicus (van der Maarel et al., 1996), D. africanus (Campbell et al., 1966), D. giganteus (Esnault et al., 1988), D. gigas(Le Gall, 1963) and D. inopinatus (Reichenbecher & Schink, 1997). Halotolerant to halophilic Desulfovibrio species have also been recovered from oilfield environments (Birkeland, 2005); these include Desulfovibrio vietnamensis (Dang et al., 1996) and D. longus (Magot et al., 1992), considered as halotolerant, and Desulfovibrio gabonensis (TardyJacquenod et al., 1996), D. capillatus (Miranda-Tello...