Thermococci

In taxonomy, the Thermococci are a class of microbes within the Euryarchaeota. They live in extremely hot environments, such as hydrothermal vents, and they have optimal growth temperatures above 80 °C. Thermococcus and Pyrococcus (literally 'balls of fire') are both obligately anaerobic chemoorganotrophs. Thermococcus prefers 70-95 °C and Pyrococcus 70-100 °C. Palaeococcus helgesonii, recently discovered in the Tyrrhenian Sea, is an aerobic chemoheterotrophic that grows at temperatures of 45-85 °C with an optimal temperature of 80 °C. Thermococcus gammatolerans sp. nov. was recently discovered in the Guaymas Basin, and it grows at temperatures from 55-95 °C with an optimal temperaturearound 88 °C with an optimal pH of 6. It has pronounced radioresistance and can survive gamma radiation at 30 kGY.