''Pyrococcus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of Thermococcaceaen

archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...

ns.See the

NCBI The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is loca ...

br>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 ba ...

'' in the respect that they are all

thermophilic A thermophile is a type of extremophile that thrives at relatively high temperatures, between . Many thermophiles are archaea, though some of them are bacteria and fungi. Thermophilic eubacteria are suggested to have been among the earliest bact ...

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 1.9 Mb followed by '' P. abyssi'' with 1.8 Mb and '' P. horikoshii'' with 1.7 Mb. The

genome 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 genes, other functional regions of the genome such as ...

s encode for many different metabolic

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

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 A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

and are enveloped by an

S-layer An S-layer (surface layer) is a part of the cell envelope found in almost all archaea, as well as in many types of bacteria. The S-layers of both archaea and bacteria consists of a Monolayer, monomolecular layer composed of only one (or, in a few c ...

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 (more accurately "diderm") bacteria. Using cryo-electron micros ...

ic space around the

cytoplasmic membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the cytoplasm, interior of a Cell (biology), cell from the extrac ...

. ''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: *Adhesive#Anaerobic, Anaerobic ad ...

but vary slightly concerning their metabolism.

Peptide Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...

fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

is the principle

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell (biology), cell. The reactants, products, and Metabolic intermediate, intermediates of an enzymatic reaction are known as metabolites, which are ...

; 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 diet ...

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 ...

, 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 Hydrothermal vents are fissures 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 hot ...

s. Optimal growth conditions include a pH level 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.

Description and significance

Phylogeny

Genome structure

Cell structure and metabolism

Ecology

See also

References

Further reading