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.

Its optimal growth pH is 6, favoring the presence of sulfur (S), which is reduced to hydrogen sulfide (H2S).

[3] Thermococcus species live in extremely hot environments such as hydrothermal vents with a growth optimum temperature above 80 °C.

Thermococcus gammatolerans was discovered in 2003 in samples collected from a hydrothermal chimney at the Guaymas Basin about 2,000 m deep off the coast of California, (27° 1' N, 111° 24' W).

gamma (γάμμα),[8] referring to gamma rays; Latin participle adjective tolerans, tolerating; Neo-Latin participle adjective gammatolerans, referring to its ability to tolerate high levels of γ-rays.