Hyperthermophile

A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upwards. An optimal temperature for the existence of hyperthermophiles is above 80 °C (176 °F). Hyperthermophiles are a subset of extremophiles, which are often micro-organisms within the domain Archaea, although some bacteria are able to tolerate temperatures of around 100 °C (212 °F), as well. Some bacteria can live at temperatures higher than 100 °C at large depths in sea where water does not boil because of high pressure. Many hyperthermophiles are also able to withstand other environmental extremes such as high acidity or radiation levels.

Hyperthermophiles were first discovered by Thomas D. Brock in 1965, in hot springs in Yellowstone National Park, Wyoming. Since then, more than 70 species have been discovered. The most hardy hyperthermophiles yet discovered live on the superheated walls of deep-sea hydrothermal vents, requiring temperatures of at least 90 °C for survival. An extraordinary heat-tolerant hyperthermophile is the recently discovered Strain 121 which has been able to double its population during 24 hours in an at 121 °C (hence its name); the current record growth temperature is 122 °C, for Methanopyrus kandleri.

Although no hyperthermophile has yet been discovered living at temperatures above 122 °C, their existence is very possible (Strain 121 survived being heated to 130 °C for two hours, but was not able to reproduce until it had been transferred into a fresh growth medium, at a relatively cooler 103 °C). However, it is thought unlikely that microbes could survive at temperatures above 150 °C, as the cohesion of DNA and other vital molecules begins to break down at this point.

Early research into hyperthermophiles speculated that their genome could be characterized by high guanine-cytosine content; however, recent studies show that "there is no obvious correlation between the GC content of the genome and the optimal environmental growth temperature of the organism."

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