Thermogladius shockii gen. nov., sp. nov., a hyperthermophilic crenarchaeote from Yellowstone National Park, USA
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A hyperthermophilic heterotrophic archaeon (strain WB1) was isolated from a thermal pool in the Washburn hot spring group of Yellowstone National Park, USA. WB1 is a coccus, 0.6–1.2 μm in diameter, with a tetragonal S-layer, vacuoles, and occasional stalk-like protrusions. Growth is optimal at 84°C (range 64–93°C), pH 5–6 (range 3.5–8.5), and <1 g/l NaCl (range 0–4.6 g/l NaCl). Tests of metabolic properties show the isolate to be a strict anaerobe that ferments complex organic substrates. Phylogenetic analysis of the 16S rRNA gene sequence places WB1 in a clade of previously uncultured Desulfurococcaceae and shows it to have ≤96% 16S rRNA sequence identity to Desulfurococcus mobilis, Staphylothermus marinus, Staphylothermus hellenicus, and Sulfophobococcus zilligii. The 16S rRNA gene contains a large insertion similar to homing endonuclease introns reported in Thermoproteus and Pyrobaculum species. Growth is unaffected by the presence of S0 or SO42−, thereby differentiating the isolate from its closest relatives. Based on phylogenetic and physiological differences, it is proposed that isolate WB1 represents the type strain of a novel genus and species within the Desulfurococcaceae, Thermogladius shockii gen. nov., sp. nov. (RIKEN = JCM-16579, ATCC = BAA-1607, Genbank 16S rRNA gene = EU183120).