In taxonomy, the Thermoplasmataceae are a family of the Thermoplasmatales. It contains only one genus, Thermoplasma. All species within Thermoplasmataceae are thermoacidophiles, and they grow at a temperature of 60°C and pH 2. They were isolated from hydrothermal vents, fumaroles and similar environments.
The genus Thermoplasma is the only described genus of the family Thermoplasmataceae and is represented by two species, T. volcanium and T. acidophilum. These facultative aerobes morphologically resemble bacterial mycoplasmas in that they do not have a cell wall or S-layer and form colonies that have a “fried-egg” appearance on agar. The Thermoplasma are obligate thermoacidophilic heterotrophs, growing optimally at 60 °C and pH 2, and are motile pleomorphic cocci. Both species genomes have been sequenced, providing additional insight to their thermoacidophilic lifestyle. Although T. acidophilum is a Euryarchaeota, it shares 58 % gene homology to the crenarchaeote Sulfolobus solfataricus, likely a result of adaptations and lateral gene transfer events due to their shared ecological niche. 16S rRNA gene sequences related to Thermoplasmataceae have been found in terrestrial solfataras, deep-sea hydrothermal vents, and several other environments, suggesting a broad niche range for this family and its relatives in the order Thermoplasmatales.