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| Pyrococcus furiosus|
Erauso et al. 1993
Pyrococcus furiosus is a heat-requiring extremophile species of Archaea, (procaryotes with a different ancestry than ordinary bacteria--and possibly everything else). It is one of the few organisms that has enzymes which contain tungsten, an element rarely found in biological molecules. The name Pyrococcus meaning 'fireball' in Latin, refers to the extremophile's round shape and its ability to grow in temperatures of around 100 degrees Celsius. The species name furiosus means 'rushing', and refers to the extremophile's doubling time.
Pyrococcus furiosus is noted for its rapid rate of reproduction (its doubling time is 37 minutes under its unusual optimal conditions). It appears as mostly regular cocci of 0.8 µm to 1.5 µm diameter with monopolar polytrichous flagellation. It grows between 70 ºC and 103 ºC, with an optimum temperature of 100 ºC, and between pH 5 and 9 (with an optimum at pH 7). It grows well on yeast extract, maltose, cellobiose, ß-glucans, starch, and protein sources (tryptone, peptone, casein and meat extracts). Growth is very slow, or nonexistent, on amino acids, organic acids, alcohols, and most carbohydrates (including glucose, fructose, lactose and galactose).
The ability to grow on polysaccharides (maltose, cellobiose, starch) but not on the monomeric sugars suggests that oligosaccharides with various degrees of polymerization may be imported into the cell, and only afterwards hydrolyzed to glucose.
Pyrococcus furiosus has an unusual glycolytic pathway: its hexokinase and phosphofructokinase hydrolize ADP, instead of ATP. Moreover, although it contains a glyceraldehyde-3-phosphate dehydrogenase, this enzyme is repressed during glycolysis. Glyceraldehyde-3-P oxidation to glycerate-3-P is instead performed in a single step (without ATP formation) by a tungsten-containing glyceraldehyde-3-P:ferredoxin oxidoreductase. Electrons released in glycolysis are transferred by a [4Fe-4S] ferredoxin to a membrane-bound hydrogenase, which reduces H+ to H2, and uses the released energy to create a proton gradient, which enables ATP synthesis through an ATP synthetase.
Pyrococcus furiosus was originally isolated anaerobically from geothermally heated marine sediments with temperatures between 90 ºC and 100 ºC collected at the beach of Porto Levante, Vulcano Island, Italy. It was first described by Dr Karl Stetter of the University of Regensburg in Germany, and a colleague, Dr Gerhard Fiala.
The sequencing of the complete genome of Pyrococcus furiosus was completed in 2001 at the University of Maryland Biotechnology Institute The Maryland team found that the genome had 1,908 kilobases, coding for 2,065 proteins.
The enzymes of Pyrococcus furiosus as would be expected, are extremely thermostable. Consequently DNA Polymerase from Pyrococcus furiosus, are often used in the Polymerase Chain Reaction, with the relevant enzyme known as Pfu. At temperatures where other interfering enzymes are destroyed, the activity of this enzyme remains.
- Fiala G, Stetter KO (1986). "Pyrococcus furiosus sp. nov. represents a novel genus of marine heterotrophic archaebacteria growing optimally at 100°C". Archives of Microbiology 145: 56–61.
- Robb FT et al. (2001). "Genomic sequence of hyperthermophile, Pyrococcus furiosus: implications for physiology and enzymology". Methods in Enzymology 330: 134–57.
- van der Oost J et al.(1998)The Ferredoxin-dependent conversion of glyceraldehyde-3-phosphate in the hyperthermophilic archaeon pyrococcus furiosus represents a novel Site of glycolytic regulation J Biol Chem 273:28149-54
- Silva PJ et al. (2000) Enzymes of hydrogen metabolism in Pyrococcus furiosus. Eur J Bioch, 267: 6541-50
- Sapra R et al.(2003) A simple energy-conserving system: Proton reduction coupled to proton translocation. Proc Natl Acad Sci USA 100:7545-50