Thermotoga
Encyclopedia
Thermotoga is a genus of the phylum Thermotogae
Thermotogae
Thermotogae is a phylum of the domain "Bacteria". This phylum comprises merely the class "Thermotogae", with the order "Thermotogales" and the family "Thermotogaceae"....

. Members of Thermotoga are hyperthermophilic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 whose cell is wrapped in an unique sheath-like outer membrane, called a "toga".

The members of the phylum stain Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 as they possess a thin peptidoglycan
Peptidoglycan
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...

 in between two lipid bilayers, albeit both peculiar. The peptidoglycan is unusual as the crosslink is not only meso-diaminopimelate as occurs in Proteobacteria
Proteobacteria
The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....

, but D-lysine.All proteinogenic amino acids are in the levo conformation, in peptidoglycan some dextro forms are present.

Lysine is synthesised from meso-diaminopimelate by Diaminopimelate decarboxylase
Diaminopimelate decarboxylase
In enzymology, a diaminopimelate decarboxylase is an enzyme that catalyzes the chemical reactionHence, this enzyme has one substrate, meso-2,6-diaminoheptanedioate, and two products, L-lysine and CO2....

.


The species are anaerobes with varying degrees of oxygen tolerance. They are capable of reducing elemental sulphur (S0) to hydrogen sulphide, which in turn can be used.

Whether thermophily is an innovation of the lineage or an ancestral trait is unclear and cannot be determined.

The genome of Thermotoga maritima was sequenced in 1999, revealing several genes of archeal origin, possibly allowing its thermophilic adaptation. The CG content of T. maritima is 46.2%; most thermophiles in fact have high CG content; this has led to the speculation that CG content may be a non-essential consequence to thermophily and not the driver towards thermophily.

Members and relatives

The type species of the genus is T. maritima, first described in 1986. At the time, it was the first species of the phylum to be described. The genus Thermotoga now contains nine official species,, while the phyum contains a single family (Thermotogaceae) with nine official genera (Fervidobacterium, Geotoga, Kosmotoga, Marinitoga, Petrotoga, Thermococcoides, Thermosipho, Thermotoga and Oceanotoga).
T. subterranea strain SL1 was found in a 70°C deep continental oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....

 reservoir in the East Paris Basin, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

.

The precise relation of the Thermotogae to other phyla is debated (v. bacterial phyla
Bacterial phyla
The bacterial phyla are the major lineages of the domain Bacteria.In the scientific classification established by Carl von Linné, each bacterial strain has to be assigned to a species , which is a lower level of a hierarchy of ranks...

): several studies have found it to be deep-branching (in Bergey's manual it appeared in fact in "Volume I: The Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

 and the deeply branching and phototrophic Bacteria"), while other have found Firmicutes to be deep-branching with Thermotogae clustering away from the base.

Name

The paper and the chapter in Bergey's manual were authored by several authors including the microbiologists Karl Stetter
Karl Stetter
Karl Otto Stetter is a German microbiologist and authority on astrobiology. He is an expert on microbial life at high temperatures.-Career:...

 and Carl Woese
Carl Woese
Carl Richard Woese is an American microbiologist and physicist. Woese is famous for defining the Archaea in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. He was also the originator of the RNA world hypothesis in 1977,...

.

The Neolatin feminine name "thermotoga" means "the hot outer garment", being a combination of the Greek
noun θέρμη (therme, heat) or more correctly the adjective θερμός , ή, όν (thermos, e, on, hot) and the Latin feminine noun toga
Toga
The toga, a distinctive garment of Ancient Rome, was a cloth of perhaps 20 ft in length which was wrapped around the body and was generally worn over a tunic. The toga was made of wool, and the tunic under it often was made of linen. After the 2nd century BC, the toga was a garment worn...

(the Roman outer garment).
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