A strictly anaerobic, thermophilic bacterium, designated strain B2-1T, was isolated from microbial mats colonizing a runoff channel formed by free-flowing thermal water from a Great Artesian Basin, Australia, bore well (registered number 17263). The cells of strain B2-1T were slightly curved rods (3.0-3.5 0.6-0.7 mm) which stained Gram-negative. The strain grew optimally in tryptone-yeast extract-glucose medium at 50 6C (temperature growth range 30-55 6C) and a pH of 8 (pH growth range 6.5-9). Strain B2-1T grew poorly on yeast extract (0.2 %) and/or tryptone (0.2 %), which were obligately required for growth on other energy sources, including a range of other carbohydrates and organic acids, but not amino acids. The end-products of glucose fermentation were ethanol and acetate. In the presence of 0.2% yeast extract, iron(III), manganese(IV) and elemental sulfur were reduced but sulfate, thiosulfate, sulfite, nitrate and nitrite were not reduced. Growth was inhibited by chloramphenicol, streptomycin, tetracycline, penicillin, ampicillin, sodium azide and by NaCl concentrations greater than 4% (w/v). The DNA G+C content was 48ᱠmol% as determined by the thermal denaturation method. 16S rRNA gene sequence analysis indicated that strain B2-1T was a member of the family Clostridiaceae, class Clostridia, phylum Firmicutes and was most closely related to Geosporobacter subterraneus DSM 17957T (89.9% similarity). On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain B2-1T is considered to represent a novel species of a new genus, for which the name Thermotalea metallivorans gen. nov., sp. nov. is proposed. The type strain is B2-1T (5KCTC 5625T5JCM 15105T5DSM 21119T).