Downloaded from www.microbiologyresearch.org by IP: 93.91.26.109 On: Fri, 15 Jan 2016 07:55:50 Desulfotomaculum hydrothermale sp. nov., a thermophilic sulfate-reducing bacterium isolated from a terrestrial Tunisian hot spring Olfa Haouari, 1,2 Marie-Laure Fardeau, 1 Jean-Luc Cayol, 1 Corinne Casiot, 3 Franc ¸ oise Elbaz-Poulichet, 3 Moktar Hamdi, 2 Manon Joseph 1 and Bernard Ollivier 1 Correspondence Bernard Ollivier bernard.ollivier@univmed.fr 1 IRD, UMR 180, Microbiologie et Biotechnologie des Environnements Chauds, IFR-BAIM, ESIL, Universite ´ s de Provence et de la Me ´ diterrane ´ e, 163 Avenue de Luminy, F-13288 Marseille Cedex 09, France 2 Laboratoire d’E ´ cologie et de Technologie Microbiennes INSAT, 1080 Tunis, Tunisia 3 Laboratoire Hydrosciences Montpellier, UMR 5569, Universite ´ s Montpellier 2 et 1, CNRS, IRD, Place E. Bataillon, Case MSE, 34095 Montpellier Cedex 05, France A novel strictly anaerobic, moderately thermophilic, sulfate-reducing bacterium, designated strain Lam5 T , was isolated from a hot spring in north-east Tunisia and was characterized phenotypically and phylogenetically. The isolate stained Gram-negative but had a Gram-positive-type cell wall. The strain comprised endospore-forming, slightly curved rod-shaped cells with peritrichous flagella. It did not possess desulfoviridin. Strain Lam5 T grew anaerobically at 40–60 6C (optimally at 55 6C) and at pH 5.8–8.2 (optimally at pH 7.1); it did not require NaCl but tolerated concentrations up to 1.5 % (w/v). It utilized lactate, pyruvate, formate, ethanol, butanol, glycerol, propanol and H 2 (plus acetate) as electron donors. Lactate was oxidized and pyruvate was fermented to acetate. Sulfate, sulfite, thiosulfate, As(V) and Fe(III) (but not elemental sulfur, fumarate, nitrate or nitrite) were used as electron acceptors. The G+C content of the genomic DNA was 46.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing showed that strain Lam5 T was a member of the genus Desulfotomaculum, with Desulfotomaculum putei as its closest relative (96 % similarity to the type strain). On the basis of genotypic, phenotypic and phylogenetic data, strain Lam5 T represents a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum hydrothermale sp. nov. is proposed. The type strain is Lam5 T (5DSM 18033 T 5JCM 13992 T ). Micro-organisms associated with hot springs in geothermal areas have attracted considerable interest in recent years. Because the primary production in these extreme environ- ments is probably sustained by hydrogen-oxidizing bac- teria, special attention has been paid to the microaerophilic members of the order Aquificales (Aguiar et al., 2004), which are recognized as dominant hydrogen oxidizers within terrestrial hot springs (Reysenbach et al., 1994; Hugenholtz et al., 1998; Reysenbach & Shock, 2002). In addition to hydrogen oxidation performed under micro- aerophilic conditions by members of the Aquificales, hydrogen oxidation occurring under anaerobiosis is also important in hot springs, as temperature and sulfide concentrations can be involved in maintaining a low redox potential in situ. Under these physicochemical conditions, sulfate-reducing bacteria (SRB) may therefore contribute significantly to hydrogen oxidation in these extreme environments, where sulfate is not limiting (Fishbain et al., 2003). It is therefore not surprising that several cultivation-based and culture-independent molecular phylogenetic surveys have provided evidence of a wide diversity of SRB inhabiting geothermal terrestrial hot springs (Blank et al., 2002; Ferris et al., 2003; Fishbain et al., 2003; Hugenholtz et al., 1998; Meyer-Dombard et al., 2005; Skirnisdottir et al., 2000). Most of the SRB isolated so far from terrestrial hot springs, with the exception of the crenarchaeote Caldivirga maquilingensis (Itoh et al., 1999), have been reported to oxidize hydrogen. They comprise bacterial members of (i) the genus Thermodesulfobacterium (Zeikus et al., 1983; Sonne-Hansen & Ahring 1999), representing one of the deepest branches within the Abbreviation: SRB, sulfate-reducing bacteria. The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains Lam5 T and Lam7 are EF081293 and EF494253, respectively. International Journal of Systematic and Evolutionary Microbiology (2008), 58, 2529–2535 DOI 10.1099/ijs.0.65339-0 65339 G 2008 IUMS Printed in Great Britain 2529