''Haloterrigena turkmenica'' is an aerobic chemo organotrophic archeon originally found in Turkish salt lakes.

Discovery

''Haloterrigena turkmenica'' is a

halophilic The halophiles, named after the Greek word for "salt-loving", are extremophiles that thrive in high salt concentrations. While most halophiles are classified into the domain Archaea, there are also bacterial halophiles and some eukaryotic species, ...

archeon that was first isolated from sulfate saline soil located in Turkmenistan. However, it wasn't until 2008 that ''H. turkmenica'' was successfully grown in the lab on Horikoshi medium. The Horikoshi medium is composed of yeast extract, glucose, potassium phosphate (KHPO₄),

peptone Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

, Magnesium sulfate (MgSO₄), water, and

sodium carbonate Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

(NaCO₃). ''Haloterrigena turkmenica'' was initially placed in the family

Halobacteriaceae In taxonomy, the Halobacteriaceae are a family of the Halobacteriales in the domain Archaea.See the NCBIbr>webpage on Halobacteriaceae Data extracted from the ''Halobacteriaceae'' represent a large part of halophilic Archaea, along with member ...

as ''

Halococcus ''Halococcus'' (common abbreviation: ''Hcc.'') is a genus (biology), genus of the Halococcaceae. Ecology ''Halococcus'' is a genus of extreme halophilic archaea, meaning that they require high salt levels, sometimes as high as 32% NaCl, for o ...

turkmenicus'' by Zyaginsteva and Tarasov in 1987. In 1999, Ventosa et al. published a proposal that would transfer the following species to ''Haloterrigena turkmenica'', which is a new genera: ''Halococcus turkmenicus,

Halobacterium ''Halobacterium'' (common abbreviation ''Hbt.'') is a genus in the family Halobacteriaceae. The genus ''Halobacterium'' ("salt" or "ocean bacterium") consists of several species of Archaea with an aerobic metabolism which requires an environment ...

trapanicum JCM 9743'' and strain GSL-11. The proposal was in response to Ventosa having found significant genetic differences between ''H. turkmenicus'' and other organisms in the ''Halococcus'' genera. The proposal was accepted and the organism is now classified under this new novel genera.

Etymology

The name ''Haloterrigena'' comes from the ''halos'' which mean salt and ''terrigena'' which means of or from Earth. ''Turkmenica'' was proposed by Zvyaginseva and Tarasov in 1987. This name comes from the fact that this species was first collected from the Turkish salt lakes.

Characterization

''Haloterrigena turkmenica'' is a gram-negative organism. Cells are typically found as individuals, but have been seen in the form of pairs and tetrads. Cell shape can be classified as being ovoid to coccoid in shape. The diameter of the cells ranges from 1.5 µm to 2.0 µm. On growth medium, colonies of ''H. turkmenica'' appear elevated, red in color and circular. The red color is due to the presence of C50-

carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...

s. There have been conflicting reports on the optimum growth temperature. According to Selim et al., the optimum growth temperature for ''H. turkmenica'' is 40 °C, while Saunders et al. reports that the optimum growth temperature is 51 °C. However, both reports state that the temperature growth range is between 29°-57 °C. ''H. turkmenica'' has been documented to best grow at NaCl concentrations around 3.4M. However, it can tolerate salt concentrations from 2-4.5M NaCl. At a pH of 9, ''H. turkmenica'' has been shown to grow best. It will tolerate a pH within the range of 8.5 to 11. ''Haloterrigena turkmenica'' is classified as an aerobic chemo-organotroph. This organism uses oxygen its preferred terminal electron acceptor and uses organic compounds for its carbon and energy source. No motility was observed. ''H. turkmenica'' tested positive for both

oxidase In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...

and

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...

activity. Also according to Selim et al., ''H. turkmenica'' is also able to hydrolyze tweens 80 (a branded version of polysorbate 80), casein, and cellulose. Acid is produced from glucose, mannose,

fructose Fructose, or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galacto ...

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...

, ribose and

xylose Xylose ( grc, ξύλον, , "wood") is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional gro ...

fermentation. This organism has been found to use the following substrates for growth: glycerol, propionate, citrate, and sodium acetate. Nitrite reduction occurs without the production of gas. ''H. turkmenica'' has a generation time of 1.5 hours, under optimal growth conditions, making it the fastest growing member of

Phylogeny and Genome

''Haloterrigena turkmenica'' is in the domain of

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 Archaebac ...

are identified as being separate from bacteria and

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

s based on ribosomal RNA ( rRNA) analysis and certain defining characteristics that separate the three domains of life as described by Woese in 1990. Rapid Annotation via Subsystems Technology ( RAST) is a service that annotates archaeal and bacterial genomes and provides comparison of phylogenetic relationships across a phylogenetic tree. Using RAST, ''Haloterrrigena turkmenica'' relatives were determined. Each relative was given a similarity score: higher scores equate to a closer phylogenetic similarity. The scores are based on the number of similar protein-coding genes out of a pool of 2959 protein-coding sequences. The following organisms are the 5 closest relatives to ''H. turkmenica'' (similarity scores in bold): # ''Haloterrigena borinquense DM 11551'' (515) # ''Haroarcula marimortui ATCC 43049'' (506) # ''Halomicrobium mukohataei DSM 12286'' (501) # ''Halorhabdus utahensis DS 12940'' (497) # ''Halquadratum walsbyi DSM 1679'' (488) In 2016, Selim et al. used a Roche DNA sequencer (GS De Novo Assembler V.2.9) to determine the GC (Guanine - Cytosine) content of ''H. turkmenica's'' genome. The GC content of ''H. turkmenica'' was determined to be 64% for its draft genome with 49 RNA genes predicted using RAST. The protein coding sequences were also digested using RAST. This revealed 193 subsystems including several enzymes encoding genes for carboxylase, cellulase and

xylanase Endo-1,4-β-xylanase (EC 3.2.1.8, systematic name 4-β-D-xylan xylanohydrolase) is any of a class of enzymes that degrade the linear polysaccharide xylan into xylose, thus breaking down hemicellulose, one of the major components of plant cell w ...

enzymes,

xylose isomerase In enzymology, a xylose isomerase () is an enzyme that catalyzes the interconversion of D-xylose and D-xylulose. This enzyme belongs to the family of isomerases, specifically those intramolecular oxidoreductases interconverting aldoses and ketos ...

, and carboxylesterase. Other genes coding for biosynthesis of peptides and secondary metabolites were also detected.

Importance

Historically the phylogeny of the genera of ''Haloterrigena'' has been difficult to classify. Further investigation could help to solidify the phylogeny of this archeon; solidification of the relationships among the members of ''Haloterrigena'' and ''Natrinema'' will help us to flesh out the

l portion of the tree of life. Investigation of

's extremophile tendencies could lead to insight into novel technologies (such as DNA preservation) and may also provide insight into the biota of early Earth.

Methanogenesis Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group ...

is only performed by members of

Archea 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 Archaeb ...

and thus it is important to discover as much as we can about this domain. ''Haloterrigena turkmenica'' is a good candidate for research because it has the fastest known generation time within

and it can be grown on media.

References

External links

Type strain of ''Haloterrigena turkmenica'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q25860687 Halobacteria