Thermococcus gammatolerans
Thermococcus gammatolerans is a gram-negative archaeon 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 (8,500 ft) by submersible Nautile during the 1991 Guaynaut cruise.
Source: Wikipedia — Thermococcus gammatolerans (CC BY-SA 4.0)