Acetoanaerobium pronyense sp. nov., an anaerobic alkaliphilic bacterium isolated from the Prony alkaline Hydrothermal Field in New Caledonia

International audience; A novel anaerobic bacterium, strain ST07-YET, was isolated from a carbonate chimney of the Prony Hydrothermal Field (PHF) in New Caledonia. Cells were Gram-positive-staining, straight rods (0.7-0.8 x 3.0-5.0 µm). They were motile by the means of lateral flagella. Strain ST07-YET was mesophilic (optimum 35°C), moderately alkaliphilic and halotolerant (optimum pH 8.7 and 5 g l-1 NaCl). Elemental sulfur, sulfate, thiosulfate, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Yeast extract, peptone, tryptone, casamino-acids, crotonate, pyruvate, galactose, maltose, sucrose, ribose, trehalose and glucose were used as carbon sources. Glucose fermentation led to acetate, H2 and CO2 formation. Arginine, serine, histidine, lysine, methionine and cysteine improved growth, but the Stickland reaction was negative for the combinations of amino acids tested. The major metabolic products from yeast extract fermentation were H2, acetate, butyrate, isobutyrate, isovalerate and propionate. The predominant cellular fatty acids were C16:0, C16:1 cis9, C14:0 and C16:1 cis7 (>5% of total fatty acids). The G+C content of the genomic DNA was 32.9 mol %. Phylogenetic analysis revealed that strain ST07-YET was most closely related to Clostridium sticklandii DSM 159T and Acetoanaerobium noterae NOT-3T (96.7% and 96.8% 16S rRNA gene sequence identity). On the basis of phylogenetic, chemotaxonomic and physiological properties, strain ST07-YET (= DSM 27512 = JCM 19400) is proposed as a novel species of the genus Acetoanaerobium, order Clostridiales, phylum Firmicutes, as Acetoanaerobium pronyense sp. nov..