What is the term for bacteria that thrive in extremely hot environments?

Bacteria that thrive in very hot environments are called thermophiles. They are heat-loving organisms adapted to grow at temperatures that would damage most familiar microbes.

Thermophiles occur in geothermal habitats such as hot springs, geysers, volcanic soils, and deep-sea hydrothermal vents. Their proteins, membranes, and genetic material are adapted for stability at elevated temperatures. Some thermophiles are bacteria, while many others belong to the archaeal domain.

A more extreme subgroup is the hyperthermophile, whose optimum growth temperature is generally above 80°C. That term is more specific than thermophile, but the broader word is the standard answer when a question asks for organisms that thrive in hot environments. Acidophiles instead prefer low pH, halophiles prefer high salt, and psychrophiles prefer cold conditions.

Thermophiles have also become important in biotechnology. The bacterium Thermus aquaticus produces Taq polymerase, a heat-stable enzyme that made repeated high-temperature DNA amplification practical in PCR. This connection between hot springs and laboratory genetics is one of the best-known examples of extremophile biology.