Desulfotomaculum hydrothermale sp. nov., a thermophilic sulfate-reducing bacterium isolated from a terrestrial Tunisian hot spring.

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 degrees C (optimally at 55 degrees C) 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) (=DSM 18033(T) =JCM 13992(T)).

Thermodesulfovibrio hydrogeniphilus sp. nov., a new thermophilic sulphate-reducing bacterium isolated from a Tunisian hot spring.

A new thermophilic sulphate-reducing bacterium (strain Hbr5T) was enriched and isolated from a terrestrial Tunisian hot spring. It was a non-spore-forming Gram-negative curved or vibrio-shaped bacterium. It appeared singly or in long chains and was actively motile by a polar flagellum. It possessed c-type cytochromes and desulfofuscidin. Growth occurred between 50 and 70 degrees C, with an optimum of 65 degrees C at pH 7.1. In the presence of sulphate as a terminal electron acceptor, this strain readily used H2 but formate only poorly. It could use sulphate, thiosulphate, sulphite or arsenate as electron acceptors. Its DNA G+C content was 36.1 mol%. Based on phenotypic, genomic, and phylogenetic characteristics, strain Hbr5T (=DSM 18151T, =JCM 13991T) is proposed to be assigned to a novel species of genus Thermodesulfovibrio, T. hydrogeniphilus sp. nov.

Isolation of sulfate-reducing bacteria from Tunisian marine sediments and description of Desulfovibrio bizertensis sp. nov.

Several strains of sulfate-reducing bacteria were isolated from marine sediments recovered near Tunis, Korbous and Bizerte, Tunisia. They all showed characteristics consistent with members of the genus Desulfovibrio. One of these strains, designated MB3(T), was characterized further. Cells of strain MB3(T) were slender, curved, vibrio-shaped, motile, Gram-negative, non-spore-forming rods. They were positive for desulfoviridin as bisulfite reductase. Strain MB3(T) grew at temperatures of 15-45 degrees C (optimum 40 degrees C) and at pH 6.0-8.1 (optimum pH 7.0). NaCl was required for growth (optimum 20 g NaCl l(-1)). Strain MB3(T) utilized H(2) in the presence of acetate with sulfate as electron acceptor. It also utilized lactate, ethanol, pyruvate, malate, fumarate, succinate, butanol and propanol as electron donors. Lactate was oxidized incompletely to acetate. Strain MB3(T) fermented pyruvate and fumarate (poorly). Electron acceptors utilized included sulfate, sulfite, thiosulfate, elemental sulfur and fumarate, but not nitrate or nitrite. The G+C content of the genomic DNA was 51 mol%. On the basis of genotypic, phenotypic and phylogenetic characteristics, strain MB3(T) (=DSM 18034(T)=NCIMB 14199(T)) is proposed as the type strain of a novel species, Desulfovibrio bizertensis sp. nov.