[1] 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.

It has pronounced radioresistance and can survive gamma radiation at 30 kGy.

[2] Thermococcus grows on organic substrates where there is a higher capacity of elemental sulfur.

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