Thermococcus gammatolerans

Thermococcus gammatolerans is an archaea extremophile and the most radiation-resistant organism known to exist.

Thermococcus gammatolerans
Thermococcus gammatolerans
Scientific classification
Domain:
Archaea
Phylum:
Euryarchaeota
Class:
Thermococci
Order:
Thermococcales
Family:
Thermococcaceae
Genus:
Thermococcus
Species:
T. gammatolerans
Binomial name
Thermococcus gammatolerans
Jolivet , 2003

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 (S), which is reduced to hydrogen sulfide (H
2S). It is the organism with the strongest known resistance to radiation, supporting a radiation of gamma rays from 30,000 gray (Gy).[1]

Along with the genera Palaeococcus and Pyrococcus, Thermococcus belongs to the Thermococcaceae family, sole family of the Thermococci (called "Protoarchaea" by Cavalier-Smith), a class in the phylum Euryarchaeota of Archaea.[2] Thermococcus species live in extremely hot environments such as hydrothermal vents with a growth optimum temperature above 80 °C. Thermococcus and Pyrococcus (literally "ball of fire") are both chemoorganotrophic anaerobic required. Thermococcus spp. prefer 70–95 °C, whereas Pyrococcus species prefer 70–100 °C.

The resistance to ionizing radiation of T. gammatolerans is enormous. While a dose of 5 Gy is sufficient to kill a human, and a dose of 60 Gy is able to kill all cells in a colony of E. coli, Thermococcus gammatolerans can withstand doses up to 30,000 Gy, and an instantaneous dose up to 5,000 Gy with no loss of viability.

History

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).

Mechanisms of resistance to radiation

Unlike other organisms, cell survival in T. gammatolerans is not altered by changing conditions in its growth phase, but the lack of ideal conditions and nutrients decreases its radioresistance. The system of chromosomal DNA repair shows that cells in stationary phase of growth reconstitute DNA more rapidly than cells in exponential growth phase. T. gammatolerans can slowly or quickly rebuild damaged chromosomes without loss of viability.[3]

Applications

A study has been conducted of its application to the development of new enzymatic markers that are resistant to high temperatures and their application in the study of carcinogenesis and the study of the development of mitochondrial diseases. DNA repair mechanisms of T. gammatolerans could be incorporated into the genome of higher species to improve DNA repair and reduce cellular aging.

Etymology

Thermococcus: Greek feminine noun thermê (θέρμη),[4] heat; new Latin masculine noun coccus (from Greek masculine noun kokkos (κόκκος),[5] berry), coccus; new Latin masculine noun Thermococcus, coccus existing in hot environment.[6] gammatolerans: Gr. gamma (γάμμα),[7] referring to gamma rays; Latin participle adjective tolerans, tolerating; Neolatin participle adjective gammatolerans, referring to its ability to tolerate high levels of γ-rays.[6]

References
  1. Jolivet, E; L'Haridon, S; Corre, E; Forterre, P; Prieur, D (2003). "Thermococcus gammatolerans sp. nov., a hyperthermophilic archaeon from a deep-sea hydrothermal vent that resists ionizing radiation". Int. J. Syst. Evol. Microbiol. 53 (Pt 3): 847–51. doi:10.1099/ijs.0.02503-0. PMID 12807211.
  2. Classification of phyla entry in LPSN; Euzéby, J.P. (1997). "List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet". International Journal of Systematic and Evolutionary Microbiology. 47 (2): 590–2. doi:10.1099/00207713-47-2-590. PMID 9103655.
  3. Tapias, Angels; Leplat, Christophe; Confalonieri, Fabrice (March 2009). "Recovery of ionizing-radiation damage after high doses of gamma ray in the hyperthermophilic archaeon Thermococcus gammatolerans". Extremophiles. 13 (2): 333–343. doi:10.1007/s00792-008-0221-3. PMID 19137239. S2CID 5671089.
  4. θέρμη. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  5. κόκκος. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
  6. Thermococcus entry in LPSN; Euzéby, J.P. (1997). "List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet". International Journal of Systematic and Evolutionary Microbiology. 47 (2): 590–2. doi:10.1099/00207713-47-2-590. PMID 9103655.
  7. γάμμα. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project

Further reading
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