Thermococci

Thermococci is a class of microbes within the Euryarchaeota.

They live in extremely hot environments, such as hydrothermal vents, and their optimal growth temperatures tend to be around 75 to 85 °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. Further, most Thermococci bacteria obtain their nutrition from the oxidation of organic compounds, and have a variety of nutritional categories. Some of these categories include those from mesophillic bacteria. Thermococcus gammatolerans sp. nov. was recently discovered in the Guaymas Basin, and it grows at temperatures from 55 to 95 °C with an optimal temperature around 88 °C with an optimal pH of 6. It has pronounced radioresistance and can survive gamma radiation at 30 kGy.

Thermococcus grows on organic substrates where there is a higher capacity of elemental sulfur. This archaeon mostly grows between temperatures 60–100 degrees Celsius. The average temperature where they thrive is around 85 degrees Celsius.

The DNA structure has a circular genome with around 2,353 coding sequence, and 2,306 are identified.