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Abstract
A strictly anaerobic, thermophilic bacterium, designated strain R270T, was isolated from microbial mats thriving in the thermal waters (66 °C) of a Great Artesian Basin bore (registered no. 17263) runoff channel. Cells of strain R270T were straight to slightly curved rods (3.50–6.00×0.75–1.00 μm) that stained Gram-positive, but possessed a Gram-negative cell-wall ultrastructure. Strain R270T grew optimally in tryptone-yeast extract-Casamino acids medium at 65 °C (growth temperature range between 50 and 70 °C) and at pH 7.0 (growth pH range between 6.0 and 9.0). In the presence of 0.02 and 0.10 % yeast extract, pyruvate and Casamino acids were the only substrates fermented from a wide spectrum of substrates tested. Fe(III), Mn(IV), thiosulfate and elemental sulfur were used as electron acceptors in the presence 0.2 % yeast extract, but not sulfate, sulfite, nitrate, nitrite or fumarate. Growth of strain R270T increased in the presence of Fe(III), which was reduced in the presence of peptone, tryptone, Casamino acids, amyl media, starch, pyruvate, H2 and CO2, but not in the presence of acetate, lactate, propionate, formate, benzoate, glycerol or ethanol. Growth and Fe(III) reduction were inhibited by chloramphenicol, streptomycin, tetracycline, penicillin, ampicillin and 2 % NaCl (w/v). The DNA G+C content of strain R270T was 41±1 mol% (T m) and phylogenetic analysis of the 16S rRNA gene indicated that this isolate was closely related to Thermovenabulum ferriorganovorum DSM 14006T (similarity value of 96.1 %) within the family ‘Thermoanaerobacteraceae’, class ‘Clostridia’, phylum ‘Firmicutes’. On the basis of the phylogenetic distance separating the two, together with differences in a number of key phenotypic characteristics, strain R270T represents a novel species of the genus Thermovenabulum, for which the name Thermovenabulum gondwanense sp. nov. is proposed; the type strain is R270T (=KCTC 5616T=DSM 21133T).
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