Calditerricola satsumensis gen. nov., sp. nov. and Calditerricola yamamurae sp. nov., extreme thermophiles isolated from a high-temperature compost

<jats:p>Two novel thermophilic micro-organisms, designated YMO81<jats:sup>T</jats:sup> and YMO722<jats:sup>T</jats:sup>, were isolated from a high-temperature compost (internal temperature >95 °C). The isolates were able to grow at 80 °C in a nutrient broth and in a synthetic medium. Cells were aerobic, Gram-negative rods (0.3×4.0 μm). Spore formation was not observed. Strain YMO81<jats:sup>T</jats:sup> grew at 83 °C and pH 6.9–8.9 and grew optimally at 78 °C and pH 7.5 with 2 % NaCl. For growth in a synthetic minimal medium at 70 °C, the vitamins biotin, folic acid and thiamine and the amino acids glutamine and methionine were essential for growth of both strains; at 80 °C, strain YMO81<jats:sup>T</jats:sup> also required histidine, isoleucine, leucine, lysine, phenylalanine, serine, tryptophan and valine. Cellular fatty acids of the isolates comprised mainly iso-C<jats:sub>17 : 0</jats:sub> and anteiso-C<jats:sub>17 : 0</jats:sub>. The DNA G+C contents of strains YMO81<jats:sup>T</jats:sup> and YMO722<jats:sup>T</jats:sup> were 70 and 64 mol%, respectively. When the 16S rRNA gene sequences of the isolates were compared with those of other bacteria, highest similarity was observed with <jats:italic>Planifilum yunnanense</jats:italic> LA5<jats:sup>T</jats:sup> (90 % 16S rRNA gene sequence similarity). DNA–DNA relatedness between strain YMO722<jats:sup>T</jats:sup> and strain YMO81<jats:sup>T</jats:sup> was 55 %. <jats:italic>N</jats:italic> <jats:sup>4</jats:sup>-Aminopropylspermine was identified as a major polyamine, which suggested that the isolates were distinct from other related taxa. On the basis of phylogenetic, phenotypic and chemotaxonomic analyses, we propose a new genus, <jats:italic>Calditerricola</jats:italic> gen. nov., and two novel species, the type species <jats:italic>Calditerricola satsumensis</jats:italic> sp. nov., with type strain YMO81<jats:sup>T</jats:sup> (=ATCC BAA-1462<jats:sup>T</jats:sup> =JCM 14719<jats:sup>T</jats:sup> =DSM 45223<jats:sup>T</jats:sup>), and <jats:italic>Calditerricola yamamurae</jats:italic> sp. nov., with type strain YMO722<jats:sup>T</jats:sup> (=ATCC BAA-1461<jats:sup>T</jats:sup> =JCM 14720<jats:sup>T</jats:sup> =DSM 45224<jats:sup>T</jats:sup>).</jats:p>