Isolation and characterization of Fonticella tunisiensis gen nov., sp. nov., a novel bacterium isolated from a Tunisian hot spring.

International audienceA strictly anaerobic, moderately thermophilic, halotolerant, rod-shaped bacterium, was isolated from a water sample of a Tunisian hot spring. The strain designated BELH25T was non motile with cells appearing singly or in pairs (0.4-0.6 µm x 2-6 µm). It grew at temperatures between 45°C and 70°C (optimum 55°C), pH between 6.2 and 8.0 (optimum 7.0) and NaCl concentration between 0 and 4 % (optimum 0-2.0 %). Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Strain BELH25T used cellobiose, fructose, galactose, glucose, maltose, mannose, saccharose, starch and yeast extract as electron donors. The main fermentation products from glucose metabolism were formate, acetate, ethanol and CO(2). The predominant cellular fatty acids were iso- C15:0, iso- C17:0 and anteiso-C15:0. The DNA G+C content was 37.2 mol %. Phylogenetic analysis of the small-subunit (SSU) ribosomal RNA (rRNA) gene sequence indicated that strain BELH25T had Caloramator viterbiensis and Fervidicella metallireducens as its closest relatives (identity of 92.2 and 92.1 % respectively) and that the strain was positioned approximatively equidistantly between the two genera. Based on phenotypic, phylogenetic and taxonomic characteristics, strain BELH25T is proposed as a novel species of a new genus within the order Clostridiales, family Clostridiaceae for which the name Fonticella tunisiensis is proposed. The type strain is BELH25T (= DSM 24455 T = JCM 17559T)