A strictly anaerobic, thermophilic bacterium, designated strain Y170T, was isolated from a microbial mat colonizing thermal waters of a run-off channel created by the free-flowing waters of a Great Artesian Basin (GAB) bore well (New Lorne bore; registered number 17263). Cells of strain Y170T were slightly curved rods (1.2-12 0.8-1.1 mm) and stained Gram-negative. The strain grew optimally in tryptone-yeast extract-glucose medium at 70 6C (temperature range for growth was 55-80 6C) and pH 7 (pH range for growth was 5-9). Strain Y170T grew poorly on yeast extract as a sole carbon source, but not on tryptone (0.2 %). Yeast extract could not be replaced by tryptone and was obligately required for growth on tryptone, peptone, glucose, fructose, galactose, cellobiose, mannose, sucrose, xylose, mannitol, formate, pyruvate, Casamino acids and threonine. No growth was observed on arabinose, lactose, maltose, raffinose, chitin, xylan, pectin, starch, acetate, benzoate, lactate, propionate, succinate, myo-inositol, ethanol, glycerol, amyl media, aspartate, leucine, glutamate, alanine, arginine, serine and glycine. End products detected from glucose fermentation were acetate, ethanol and presumably CO2 and H2. Iron(III), manganese(IV), thiosulfate and elemental sulfur, but not sulfate, sulfite, nitrate or nitrite, were used as electron acceptors in the presence of 0.2% yeast extract. Iron(III) in the form of amorphous Fe(III) oxhydroxide and Fe(III) citrate was also reduced in the presence of tryptone, peptone and Casamino acids, but not with chitin, xylan, pectin, formate, starch, pyruvate, acetate, benzoate, threonine, lactate, propionate, succinate, inositol, ethanol, glycerol, mannitol, aspartate, leucine, glutamate, alanine, arginine, serine or glycine. Strain Y170T was not able to utilize molecular hydrogen and/or carbon dioxide in the presence or absence of iron(III). Chloramphenicol, streptomycin, tetracycline, penicillin and ampicillin and NaCl concentrations greater than 2% inhibited growth. The G+C content of the DNA was 48ᱠmol% [SD (n53); Tm]. 16S rRNA gene sequence analysis indicated that strain Y170T is a member of the family Syntrophomonadaceae, class Clostridia, phylum Firmicutes and was most closely related to members of the genus Thermosediminibacter (mean similarity of 93.6 %). On the basis of the 16S rRNA gene sequence comparisons and physiological characteristics, strain Y170T is considered to represent a novel species of a new genus, for which the name Fervidicola ferrireducens gen. nov., sp. nov. is proposed. The type strain is Y170T (5KCTC 5610T5JCM 15106T5DSM 21121T).