''Thermococcus litoralis'' (''T. litoralis'') is a species of

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 ...

that is found around deep-sea

hydrothermal vents 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 hots ...

as well as shallow submarine thermal springs and oil wells. It is an

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 ...

organotroph An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs s ...

hyperthermophile A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upward. An optimal temperature for the existence of hyperthermophiles is often above 80 °C (176 °F). Hyperthermophiles are of ...

that is between in diameter. Like the other species in the order thermococcales, ''T. litoralis'' is an irregular hyperthermophile

coccus Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archaea ...

that grows between . Unlike many other thermococci, ''T. litoralis'' is non-motile. Its cell wall consists only of a single

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 ...

that does not form hexagonal lattices. Additionally, while many thermococcales obligately use sulfur as an electron acceptor in metabolism, ''T. litoralis'' only needs sulfur to help stimulate growth, and can live without it. ''T. litoralis'' has recently been popularized by the scientific community for its ability to produce an alternative DNA polymerase to the commonly used

Taq polymerase ''Taq'' polymerase is a thermostable DNA polymerase I named after the thermophilic eubacterial microorganism ''Thermus aquaticus,'' from which it was originally isolated by master's student Alice Chien et al. in 1976. Its name is often abbr ...

. The ''T. litoralis'' polymerase, dubbed the vent polymerase, has been shown to have a lower error rate than Taq due to its

proofreading Proofreading is a phase in the process of publishing where galley proofs are compared against the original manuscripts or graphic artworks, to identify transcription errors in the typesetting process. In the past, proofreaders would place corr ...

3’–5’

exonuclease Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. Its close relative is th ...

abilities, but higher than

Pfu polymerase ''Pfu'' DNA polymerase is an enzyme found in the hyperthermophilic archaeon ''Pyrococcus furiosus'', where it functions to copy the organism's DNA during cell division (thermostable DNA polymerase). In the laboratory setting, ''Pfu'' is used t ...

DNA polymerase

The

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create t ...

of ''Thermococcus litoralis'' is stable at high temperatures, with a

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of eight hours at and two hours at . It also has a proofreading activity that is able to reduce mutation frequencies to a level 2–4 times lower than most non-proofreading DNA polymerases.

Habitat and ecology

''T. litoralis'' grows near shallow and deep sea hydrothermal vents in extremely hot water. The optimal growth temperature for ''T. litoralis'' is 85–88 °C. It also prefers slightly acidic waters, growing between pH 4.0 to 8.0 with the optimal pH between 6.0–6.4. Unlike many other hyperthermophiles, ''T. litoralis'' is only facultatively dependent on sulfur as a final electron acceptor in fermentation, producing hydrogen gas in its absence and

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

when present. Additionally, ''T. litoralis'' has been shown to produce an

exopolysaccharide Extracellular polymeric substances (EPS) are natural polymers of high molecular weight secreted by microorganisms into their environment. EPS establish the functional and structural integrity of biofilms, and are considered the fundamental compo ...

(EPS) that could possibly help it form a

biofilm A biofilm is a Syntrophy, syntrophic Microbial consortium, community of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a slimy ext ...

. It is made of

mannose Mannose is a sugar with the formula , which sometimes is abbreviated Man. It is one of the monomers of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylatio ...

sulfites Sulfites or sulphites are chemical compound, compounds that contain the sulfite ion (IUPAC nomenclature of inorganic chemistry, systematic name: sulfate(IV) ion), . The sulfite ion is the conjugate base of bisulfite. Although its acid (sulfurous ...

, and phosphorus.

Physiology

''T. litoralis'' can utilize

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 ...

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

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

as energy sources. In a laboratory setting, ''T. litoralis'' must be supplied with amino acids in order to grow at non-reduced rates. The only amino acids it does not require are

asparagine Asparagine (symbol Asn or N) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the depro ...

glutamine Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral ...

alanine Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...

, and

glutamate Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a Essential amino acid, non-essential nutrient for humans, meaning that ...

. These amino acids may not be vital for ''T. litoralis'' because asparagine and glutamine tend to

deaminate Deamination is the removal of an amino group from a molecule. Enzymes that catalyse this reaction are called deaminases. In the human body, deamination takes place primarily in the liver; however, it can also occur in the kidney. In situations o ...

at high temperatures found around hydrothermic vents and alanine and glutamate can usually be produced by other hyperthermophilic archaea. The main carbon source for ''T. litoralis'' seems to be maltose, which can be brought into the cell via a maltose-

trehalose Trehalose (from Turkish '' tıgala'' – a sugar derived from insect cocoons + -ose) is a sugar consisting of two molecules of glucose. It is also known as mycose or tremalose. Some bacteria, fungi, plants and invertebrate animals synthesize it ...

ABC transporter The ABC transporters, ATP synthase (ATP)-binding cassette transporters are a transport system superfamily that is one of the largest and possibly one of the oldest gene families. It is represented in all extant phyla, from prokaryotes to huma ...

. ''T. litoralis'' has a specialized glycolytic pathway called the modified Embden–Meyerhoff (EM) pathway. One way the modified EM pathway in ''T. litoralis'' deviates from the common EM pathway is that the modified version contains an ADP dependent hexose kinase and PFK instead of an ATP dependent versions of the enzymes.

Novel strains

New DNA analysis has shown several isolates of ''T. litoralis'', MW and Z-1614, which are most likely new strains. MW and Z-1614 were confirmed to be strains of ''T. litoralis'' through DNA-DNA hybridization, C–G ratios (38–41 mol%), and immunoblotting analyses. They slightly differ in morphology from the previously isolated ''T. litoralis'' in that they all have flagella. Through the same processes it has been shown that the previously discovered ''Caldococcus litoralis'' was actually ''T. litoralis''. The genome for ''T. litoralis'' has yet to be fully sequenced.

References

External links