Thermococcus gammatolerans is an archaea extremophile and the most radiation-resistant organism known to exist. As reported in 2003 the type strain EJ3ᵀ was taken from a submarine hydrothermal vent in the Guaymas Basin off the coast of Baja California at a depth of about 2,600 m by submersible Nautile during the 1991 Guaynaut cruise. Thermococcus gammatolerans thrives in temperatures between 55 and 95 °C with an optimum development around 88 °C. Its optimal growth pH is 6, favoring the presence of sulfur, which is reduced to hydrogen sulfide. It is the organism with the strongest known resistance to radiation, supporting a radiation of gamma rays from 30,000 gray.