Balneicella halophila gen. nov., sp nov., an anaerobic bacterium, isolated from a thermal spring and description of Balneicellaceae fam. nov.

International audienceA mesophilic anaerobic bacterium, designated KHALHBd91(T) was isolated from the moderately hot spring of Hammam Biadha, Tunisia. The strain was Gram-staining-negative, non-sporulating, non-motile and rod-shaped, appearing singly (0.5-2.0 x 0.5-1 mu m). It grew anaerobically at temperatures between 20 and 50 degrees C (optimum 37 degrees C) and at pH values between 5.5 and 7.8 (optimum 7.0). It required NaCl for growth, with growth observed at up 8.5% and an optimum at 2.5 %. KHALHBd91(T) used glucose, galactose, maltose, pyruvate, lactate, fumarate and yeast extract as electron donors. The end-products from glucose fermentation were acetate, propionate, succinate and CO2. Nitrate, nitrite, thiosulfate, elemental sulfur, sulfate and sulfite were not used as terminal electron acceptors. The predominant cellular fatty acids were anteiso-C-15 : 0 and iso-C-15 : 0. The respiratory quinone was MK-6. The main polar lipids consisted of lipids, phospholipids, glycolipids, aminolipids, phosphoaminoglycolipids and phosphatidylethanolamine. The DNA G+C content was 35.0 mol%. Phylogenetic analysis of the small-subunit ribosomal 16S rRNA gene sequence indicated that KHALHBd91(T) had Marinifilum fragile and Marinifilum flexuosum (phylum Bacteroidetes, class Bacteroidia, order Bacteroidales) as its closest relatives (similarity of 86.7 and 87.8% respectively). The phylogenetic and physiological data fro the present study strongly indicate that the isolate represents a novel genus and species of a novel family, Balneicella halophila gen. nov., sp. nov., in the family Balneicellaceaefam. nov. The type strain is KHALHBd91(T) (=DSM28579(T) =JCM19909(T))