noun, plural: thermophiles
A thermophile is an organism that is adapted to live at relatively high temperatures, i.e. between 41 and 122 °C. Thermophiles are mostly from the domain Archaea. They occur in places such as geothermally-heated regions, e.g. hot springs, deep sea hydrothermal vents, peat bogs, and compost. They are able to thrive in such extreme temperatures because they contain enzymes that can function at high temperatures.
Thermophiles may be classified into groups such as obligate thermophiles, facultative thermophiles, and hyperthermophiles. Obligate thermophiles are those that need high temperatures in order to grow and thrive in their environment. Facultative thermophiles are those that can thrive at high temperatures as well as at relatively lower temperatures, e.g. below 50 °C. Hyperthermophiles are thermophiles that prefer temperatures above 80 °C for optimal growth. Because hyperthermophiles can withstand extremely high temperatures that would likely be detrimental to the survival of many organisms, they are a type of extremophiles.
Thermophiles are different from mesophiles. The latter grow best at moderate temperatures, i.e. 20 and 45 °C, which are not too hot and not too cold.
Word origin: thermos- (warm, hot) + phile (love)