Rhabdanaerobium thermarum gen. nov., sp. nov., a novel anaerobic bacterium isolated from a hot spring.

A novel Gram-stain-positive, obligately anaerobic and thermophilic bacterium, strain SYSU GA15001, was isolated from a sample collected from a hot spring located in Tengchong, China. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain SYSU GA15001 belonged to the family Eubacteriaceae, and was closely related to 'Irregularibacter muris' 2PG-426-CC4.2 (93.6 % similarity), Garciella nitratireducens DSM 15102 (93.2 %) and Alkalibacter saccharofermentans Z-78920 (89.7 %). Cells were rods and motile by means of a subpolar flagellum. Spores were formed in old cultures. Optimum growth was observed at 45 °C, at pH 7 and in the presence of 1.5 % (w/v) NaCl. The strain utilized d-arabinose, dulcitol, d-galactose, glucose, lactose, maltose, d-mannose, raffinose, l-rhamnose, d-sorbitol, xylitol, l-alanine, l-arginine, glycine, l-isoleucine, l-leucine, dl-methionine, NH4Cl, l-proline and l-threonine as sole carbon/nitrogen sources. Additionally, complex substrates including beef extract, peptone, starch and yeast extract can also be used as sole energy sources. The major fatty acid methyl esters were C14 : 0, anteiso-C15 : 0 and C18 : 0. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, an unidentified polar lipid, three unidentified phospholipids and an unidentified glycolipid. The DNA G+C content was determined to be 35.6 mol%. Strain SYSU GA15001 was physiologically and phylogenetically distinguishable from its closely related genera, and merits assignment as representing the type species of a new genus Rhabdanaerobium, with the name Rhabdanaerobium thermarum gen. nov., sp. nov. The type strain of the type species is SYSU GA15001 (=CGMCC 1.5219=KCTC 15623).