Thermolithobacteria is a class of rod-shaped Gram-positive bacteria within phylum Bacillota. Species within this class are thermophilic lithotrophs isolated from sediment in Calcite Springs in Yellowstone National Park. Thermolithobacter ferrireducens strain JW/KA-2(T) metabolism consists of the oxidation of hydrogen gas and reduction of ferric oxide to magnetite. Thermolithobacter carboxydivorans strain R1(T) is hydrogenic and oxidizes carbon monoxide.