Characterization of Thermosphaera chiliense sp. nov., the Second Representative of the Genus Thermosphaera, a Hyperthermophilic Hydrolytic Archaeon Fermenting Carbohydrates

Archaeal genus Thermosphaera belongs to Desulfurococcaceae family (Thermoproteota) and is represented by one described species, T. aggregans. It is anaerobic hyperthermophile with coccoid cells utilizing proteinaceous compounds and heat-treated xylan. Here we report characterization of the strain 3507 belonging to Thermosphaera. Strain 3507 had similar phenotype with T. aggregans, however can utilize wider range of substrates including different mono- and polysaccharides, and possessed resistance to oxygen. Starch fermentation products were CO2, H2, ethanol and acetate. Based on phenotypic and genomic (phylogenomic analysis, genome-based comparisons) data, we propose Thermosphaera chiliense sp. nov. with strain 3507T (=UQM 41896T) as a type strain.