thermoacidophiles

Thermoacidophiles are extremophilic microorganisms that require both high temperatures and acidic pH for growth. Most known thermoacidophiles are archaea, including genera such as Sulfolobus, Acidianus, Metallosphaera, Thermoplasma, and Picrophilus. They inhabit hot, acidic environments such as volcanic hot springs, solfataras, acidic hydrothermal vents, and metal-rich lakes.

Physiology and metabolism: Thermoacidophiles are typically chemolithoautotrophs or chemoorganoheterotrophs, obtaining energy by oxidizing reduced sulfur compounds and sometimes ferrous iron; electron acceptors may include oxygen or ferric iron. Many are aerobic or microaerophilic, with some capable of anaerobic metabolism. Growth temperatures usually range from about 50°C to over 80°C, and pH optima typically lie between 1 and 4. They possess archaeal membrane lipids with ether linkages and often tetraether lipids; many lack peptidoglycan in their cell walls. Their enzymes are highly thermostable and acid-stable, enabling metabolic activity under harsh conditions.

Taxonomy and examples: The best-studied thermoacidophiles are archaeal genera such as Sulfolobus, Acidianus, Metallosphaera, Thermoplasma, and Picrophilus. Sulfolobus species are aerobic chemolithoautotrophs that oxidize sulfur; Acidianus spp. can oxidize sulfur and reduce ferric iron; Metallosphaera sedula is known from mining and biomining. Thermoplasma species are acidophilic, cell-wall-deficient archaea; Picrophilus oshimae and related species are among the most acidophilic known, thriving at pH near 0.

Ecology and applications: They play key roles in sulfur and iron cycling in geothermal environments and influence mineral dissolution and metal cycling. Biotechnological uses include bioleaching and bioremediation under acidic, high-temperature conditions.