Thermococci

File:Schematic diagram of a Thermococcus gammatolerans cell.jpg

Schematic diagram of the Thermococcus gammatolerans cell pictured above.

File:Pyrococcus furiosus.png

Pyrococcus furiosus

Thermococci is a class of microbes within the Euryarchaeota.

They live in extremely hot environments, such as hydrothermal vents, and their optimal optimal growth temperatures tend to be around 75 to 85°C. Thermococcus and Pyrococcus (literally "balls of fire") are both obligately anaerobic chemoorganotrophs.

Thermococcus prefers 70–95 °C and Pyrococcus 70-100 °C. Palaeococcus helgesonii, recently discovered in the Tyrrhenian Sea, is an aerobic chemoheterotrophic that grows at temperatures of 45–85 °C with an optimal temperature of 80 °C. Thermococcus gammatolerans sp. nov. was recently discovered in the Guaymas Basin, and it grows at temperatures from 55 to 95 °C with an optimal temperature around 88 °C with an optimal pH of 6. It has pronounced radioresistance and can survive gamma radiation at 30 kGy.

Thermococcus grows on organic substrates where there is a higher capacity of elemental sulfur. This archaeon mostly grows between temperatures 60–100 degrees Celsius. The average temperature where they thrive is around 85 degrees Celsius.

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

Taxonomy

This class encompasses the hyperthermophilic members of Methanobacteriota that have a sulfur-based anaerobic respiration. There is only one widely recognized order within Thermococci, Thermococcales. Another proposed but not yet widely accepted order is Candidatus Methanofastidiosales. Thermococcales encompasses the family Thermococcaceae, which is composed of three genus: Palaeococcus, Pyrococcus and Thermococcus. Palaeococcus encompasses 3 species, while Pyrococcus and Thermococcus encompass 24 and 179 species, respectively.

See also

• List of Archaea genera

Further reading

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