What is "thermococcus"

In taxonomy, Thermococcus is a genus of extreme thermophiles in the family the Thermococcaceae.
Members of the genus Thermococcus are all Archaea, having thermophillic-hyperthermophillic characteristics. These microorganisms are typically irregularly shaped coccoid species, ranging in size from 0.6-2.0 μm in diameter. Some species of Thermococcus are immobile, and some species have motility, using flagella as their main source of movement. These flagella typically exist at a specific pole of the organism. This movement has been seen at room temperature or at high temperature, depending on the specific organism. In some species, these microorganisms can aggregate and form white-gray plaques, while all of these organisms dwell in temperatures from 70-<100oC, either in the presence of black smokers (hydrothermal vents), or freshwater springs, amongst salt (NaCl) concentrations of 1%-3%. Species in this genus are strictly anaerobes, and most are barophiles as well as thermophiles, living in depths between 200-<1000 ft. These organisms thrive at pH levels of 5.6-7.9. Members of this genus have been found in many hydrothermal vent systems in the world, including from the seas of Japan, to off the coasts of California. Surprisingly salt (NaCl) is not a required substrate for these organisms, as one study showed Thermococcus members living in fresh hot water systems in New Zealand, however they do require a low concentration of lithium ion for growth. Thermococcus members are described as heterotrophic, chemotrophic and organotrophic sulfanogens; utilizing elemental sulfur (So) and carbon sources including amino acids, carbohydrates, and organic acids such as pyruvate.