Thermoproteus thermophilus sp. nov., a hyperthermophilic crenarchaeon isolated from solfataric soil

A hyperthermophilic crenarchaeon, designated strain CBA1502T, was isolated from volcanic soil in the Mayon volcano in the Philippines. The 16S rRNA gene sequence of strain CBA1502T was most closely related to that of Thermoproteus uzoniensis DSM 5263T (99.2% similarity) and Thermoproteus tenax Kra 1T (99.0%). The organism grew at 75-90°C and pH 4.0-6.0 and in the presence of 0-0.5% (w/v) NaCl, with optimal growth at 85°C and pH 5.0. Strain CBA1502T utilized d-arabinose, beef extract, Casamino acids, formate, fumarate, peptone, pyruvate, trimethylamine and yeast extract as energy substrates, and d-arabinose, formate, pyruvate and yeast extract as carbon sources. Fumarate, sulfate, sulfur and thiosulfate functioned as electron acceptors, but not ferric chloride, nitrate, malate or oxidized glutathione. DNA-DNA hybridization studies showed that there was less than 46.1% relatedness between strain CBA1502T and other members of the genus Thermoproteus. The DNA G+C content of strain CBA1502T was 62.0 mol%. We conclude that, according to its phylogenetic, phenotypic and genotypic characteristics, strain CBA1502T represents a novel species of the genus Thermoproteus, and propose the name Thermoproteus thermophilus sp. nov., with the type strain CBA1502T ( = ATCC BAA-2416T = JCM 17229T).