''Pyrococcus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Thermococcaceae In taxonomy, the Thermococcaceae are a family of the Thermococcales. Almost all species within the three genera of Thermococcaceae were isolated from hydrothermal vents in the ocean. All are strictly anaerobe An anaerobic organism or anaerobe ...

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaeba ...

n.See the NCBIbr>webpage on Pyrococcus
Data extracted from the

Description and significance

''Pyrococcus'' has similar characteristics of other thermoautotrophican

such as '' Archaeoglobus'', and ''

Methanococcus ''Methanococcus'' is a genus of coccoid methanogens of the family Methanococcaceae. They are all mesophiles, except the thermophilic '' M. thermolithotrophicus'' and the hyperthermophilic '' M. jannaschii''. The latter was discovered at the b ...

'' in the respect that they are all

thermophilic A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...

and anaerobic. ''Pyrococcus'' differs, however, because its optimal growth temperature is nearly 100 °C and dwells at a greater sea depth than the other archaea. Studying ''Pyrococcus'' helps give insight to possible mechanisms used to endure extreme environmental conditions like high temperatures and high pressure.

Phylogeny

Genome structure

Three of the ''Pyrococcus'' species have been sequenced. '' P. furiosus'' is the largest containing 1.9Mb followed by '' P. abyssi'' with 1.8Mb and '' P. horikoshii'' with 1.7Mb. The

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...

s encode for many different metabolic

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s which gives themselves a wider spectrum of living conditions because they can transport and metabolize a wide range of organic substances. Variation was detected between species as well.

Cell structure and metabolism

The cells of ''Pyrococcus'' are about 0.8–2 μm and are slightly irregular cocci in shape. They show a polar grouping of flagella and are enveloped by an S-layer enclosing a

periplasm The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found that ...

ic space around the

cytoplasmic membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (th ...

. ''Pyrococcus'' species are

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

but vary slightly concerning their metabolism. Peptide fermentation is the principle

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical ...

however, growth has been observed for ''P. furiosus'' and ''P. abyssi'' on

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human die ...

maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the tw ...

, and

pyruvate Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic a ...

but not for ''P. horikoshii''. While the presence of elemental sulfur is not needed for growth, growth is enhanced with the addition of S^o.

Ecology

''Pyrococcus'' species inhabit environments with extremely high temperatures such as

Hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspo ...

s. Optimal growth conditions include a

pH level In chemistry, pH (), historically denoting "potential of hydrogen" (or "power of hydrogen"), is a scale used to specify the acidity or basicity of an aqueous solution. Acidic solutions (solutions with higher concentrations of ions) are me ...

of about 7, a salt concentration around 2.5%, and a temperature around 98 °C. Growing in temperatures this high, it is easy to see why they are anaerobic since at these boiling temperatures hardly any oxygen will be available. In the example of Hydrothermal vents, where ''P. abyssi'' has been found, there is no sunlight and the pressure is around 200 atm in addition to the extremely high temperature.

References

External links

Archaea genera {{archaea-stub

Description and significance

Phylogeny

Genome structure

Cell structure and metabolism

Ecology

References

Further reading

Scientific journals

Scientific books

Scientific databases

External links