Haloquadratum

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Haloquadratum
Haloquadratum walsbyi00.jpg
Scientific classification
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Haloquadratum

Burns et al. 2007
Type species
Haloquadratum walsbyi
Burns et al. 2007
Species

Haloquadratum (common abbreviation: Hqr.) is a genus of archaean, belonging to the family Haloferacaceae. [1] The first species to be identified in this group, Haloquadratum walsbyi, is unusual in that its cells are shaped like square, flat boxes. [2]

Contents

This halophilic archaean, discovered in 1980 by A.E. Walsby in the Gavish Sabkha, [3] a coastal hypersaline pool (sabkha) on the Sinai Peninsula in Egypt, was not cultured until 2004. [4]

The cells typically contain polyhydroxyalkanoate (PHA) granules, as well as large numbers of refractile, gas-filled vacuoles which provide buoyancy in a watery environment and may help to position the cells to maximize light-harvesting. [5] The cells may join with others to form fragile sheets up to 40 micrometres wide.

H. walsbyi can be found anywhere[ citation needed ] in hypersaline waters. When sea water evaporates, high concentration and precipitation of calcium carbonate and calcium sulfate result, leading to a hypersaline sodium chloride-rich brine. Further evaporation results in the precipitation of sodium chloride or halite, and then to a concentrated magnesium chloride brine termed bittern. During the final stage of halite formation, before magnesium chloride concentration causes the brine to become sterile, H. walsbyi flourishes and can make up 80% of the brine's biomass.

Description and significance

H. walsbyi was first discovered in 1980 by A.E. Walsby in the Gavish Sabkha, a coastal brine pool in the Sinai peninsula, Egypt, and formally described by Burns et al. in 2007. [4] The organisms were notable because of their extremely thin (around 0.15 μm), square-shaped structure. It was not cultivated in the lab until 2004.

Genome structure

The mapping of H. walsbyi's genome has been completed, giving a better understanding of the organism's genealogy and taxonomy, and the role it plays in the ecosystem. [6] A genomic comparison of the Spanish and Australian isolates (strains HBSQ001 and C23T) strongly suggests a rapid global dispersion, as they are so similar and have retained gene order (synteny). [7]

Cell structure and metabolism

H.walsbyi has a unique cell shape – that of an extremely thin square, its best-known characteristic. The cells possess an abundance of intracellular refractile bodies known as gas vacuoles – vacuoles filled with gas which provide buoyancy – maintaining upper position in the water column. Individual square cells are joined with others to form large sheets, sometimes as large as 40 μm. These sheets are extremely fragile and the connections between the cells are easily broken.

Its mode of metabolism is not completely known; complete genetic information will give researchers necessary insight.

Ecology

H. walsbyi was first noticed and taken from saline pools in Egypt, but it can be found in hypersaline bodies of water all over the world. Evaporation of water in these pools leaves high concentrations of salt, making for its optimal growth environment. According to Bolhuis et al., "In this sense, they are the most hyperhalophilic organisms known, as further concentration of the magnesium salts (bitterns) leads to sterility of the brines." Its precise role in the ecosystem is not known for sure, but because of its unique morphology, learning more about it will surely provide some information on the evolution and morphological adaptation of archaeans.

See also

Related Research Articles

A halophile is an extremophile that thrives in high salt concentrations. In chemical terms, halophile refers to a Lewis acidic species that has some ability to extract halides from other chemical species.

Halotolerance is the adaptation of living organisms to conditions of high salinity. Halotolerant species tend to live in areas such as hypersaline lakes, coastal dunes, saline deserts, salt marshes, and inland salt seas and springs. Halophiles are organisms that live in highly saline environments, and require the salinity to survive, while halotolerant organisms can grow under saline conditions, but do not require elevated concentrations of salt for growth. Halophytes are salt-tolerant higher plants. Halotolerant microorganisms are of considerable biotechnological interest.

<span class="mw-page-title-main">Brine</span> Concentrated solution of salt in water

Brine is water with a high-concentration solution of salt. In diverse contexts, brine may refer to the salt solutions ranging from about 3.5% up to about 26%. Brine forms naturally due to evaporation of ground saline water but it is also generated in the mining of sodium chloride. Brine is used for food processing and cooking, for de-icing of roads and other structures, and in a number of technological processes. It is also a by-product of many industrial processes, such as desalination, so it requires wastewater treatment for proper disposal or further utilization.

<span class="mw-page-title-main">Sea salt</span> Salt produced from the evaporation of seawater

Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea salt has been dated to prehistoric times.

<span class="mw-page-title-main">Salt lake</span> Landlocked body of water which has a high concentration of salts

A salt lake or saline lake is a landlocked body of water that has a concentration of salts and other dissolved minerals significantly higher than most lakes. In some cases, salt lakes have a higher concentration of salt than sea water; such lakes can also be termed hypersaline lakes, and may also be pink lakes on account of their colour. An alkalic salt lake that has a high content of carbonate is sometimes termed a soda lake.

<i>Halobacterium</i> Genus of archaea

Halobacterium is a genus in the family Halobacteriaceae.

Halobacteriaceae is a family in the order Halobacteriales and the domain Archaea. Halobacteriaceae represent a large part of halophilic Archaea, along with members in two other methanogenic families, Methanosarcinaceae and Methanocalculaceae. The family consists of many diverse genera that can survive extreme environmental niches. Most commonly, Halobacteriaceae are found in hypersaline lakes and can even tolerate sites polluted by heavy metals. They include neutrophiles, acidophiles, alkaliphiles, and there have even been psychrotolerant species discovered. Some members have been known to live aerobically, as well as anaerobically, and they come in many different morphologies. These diverse morphologies include rods in genus Halobacterium, cocci in Halococcus, flattened discs or cups in Haloferax, and other shapes ranging from flattened triangles in Haloarcula to squares in Haloquadratum, and Natronorubrum. Most species of Halobacteriaceae are best known for their high salt tolerance and red-pink pigmented members, but there are also non-pigmented species and those that require moderate salt conditions. Some species of Halobacteriaceae have been shown to exhibit phosphorus solubilizing activities that contribute to phosphorus cycling in hypersaline environments. Techniques such as 16S rRNA analysis and DNA-DNA hybridization have been major contributors to taxonomic classification in Halobacteriaceae, partly due to the difficulty in culturing halophilic Archaea.

<span class="mw-page-title-main">Saltern</span> Area or installation for making salt

A saltern is an area or installation for making salt. Salterns include modern salt-making works (saltworks), as well as hypersaline waters that usually contain high concentrations of halophilic microorganisms, primarily haloarchaea but also other halophiles including algae and bacteria.

<span class="mw-page-title-main">Haloarchaea</span> Class of salt-tolerant archaea

Haloarchaea are a class of prokaryotic organisms under the archaeal phylum Euryarchaeota, found in water saturated or nearly saturated with salt. Halobacteria are now recognized as archaea rather than bacteria and are one of the largest groups. The name 'halobacteria' was assigned to this group of organisms before the existence of the domain Archaea was realized, and while valid according to taxonomic rules, should be updated. Halophilic archaea are generally referred to as haloarchaea to distinguish them from halophilic bacteria.

<span class="mw-page-title-main">Sabkha</span> Salt lake above the tide line, where evaporite deposits accumulate

A sabkha is a coastal, supratidal mudflat or sandflat in which evaporite-saline minerals accumulate as the result of semiarid to arid climate. Sabkhas are gradational between land and intertidal zone within restricted coastal plains just above normal high-tide level. Within a sabkha, evaporite-saline minerals sediments typically accumulate below the surface of mudflats or sandflats. Evaporite-saline minerals, tidal-flood, and aeolian deposits characterize many sabkhas found along modern coastlines. The accepted type locality for a sabkha is at the southern coast of the Persian Gulf, in the United Arab Emirates. Evidence of clastic sabkhas are found in the geological record of many areas, including the UK and Ireland. Sabkha is a phonetic transliteration of the Arabic word used to describe any form of salt flat. A sabkha is also known as a sabkhah,sebkha, or coastal sabkha.

<i>Haloarcula</i> Genus of archaea

Haloarcula is a genus of extreme halophilic Archaea in the class of Halobactaria.

Halorubrum is a genus in the family Halorubraceae. Halorubrum species are usually halophilic and can be found in waters with high salt concentration such as the Dead Sea or Lake Zabuye.

In taxonomy, Natrialba is a genus of the Natrialbaceae. The genus consists of many diverse species that can survive extreme environmental niches, especially they are capable to live in the waters saturated or nearly saturated with salt (halophiles). They have certain adaptations to live within their salty environments. For example, their cellular machinery is adapted to high salt concentrations by having charged amino acids on their surfaces, allowing the cell to keep its water molecules around these components. The osmotic pressure and these amino acids help to control the amount of salt within the cell.

Natronomonas is a genus of the Halobacteriaceae.

<i>Dunaliella</i> Genus of algae

Dunaliella is a single-celled, photosynthetic green alga, that is characteristic for its ability to outcompete other organisms and thrive in hypersaline environments. It is mostly a marine organism, though there are a few freshwater species that tend to be more rare. It is a genus in which certain species can accumulate relatively large amounts of β-carotenoids and glycerol in very harsh growth conditions consisting of high light intensities, high salt concentrations, and limited oxygen and nitrogen levels, yet is still very abundant in lakes and lagoons all around the world.

<span class="mw-page-title-main">Bittern (salt)</span> Solution from evaporation of seawater or brine

Bittern, or nigari, is the salt solution formed when halite precipitates from seawater or brines. Bitterns contain magnesium, calcium, and potassium ions as well as chloride, sulfate, iodide, and other ions.

Chlorine gas can be produced by extracting from natural materials, including the electrolysis of a sodium chloride solution (brine) and other ways.

<span class="mw-page-title-main">A.E. Walsby</span>

Anthony Edward Walsby, BSc(Birm), PhD(Lond), FRS, is the Emeritus Professor of Microbiology at the School of Biological Sciences, University of Bristol.

<i>Haloquadratum walsbyi</i> Species of halotolerant archaea

Haloquadratum walsbyi is a species of Archaea in the genus Haloquadratum, known for its square shape and halophilic nature.

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

References

  1. See the NCBI webpage on Haloquadratum. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information . Retrieved 2007-03-19.
  2. Stoeckenius W (1 October 1981). "Walsby's square bacterium: fine structure of an orthogonal procaryote". J. Bacteriol. 148 (1): 352–60. doi:10.1128/JB.148.1.352-360.1981. PMC   216199 . PMID   7287626.
  3. Walsby, A. E. (1980). "A square bacterium". Nature. 283 (5742): 69–71. Bibcode:1980Natur.283...69W. doi:10.1038/283069a0. S2CID   4341717.
  4. 1 2 Burns, D. G.; Janssen, P. H.; Itoh, T.; Kamekura, M.; Li, Z.; Jensen, G.; Rodriguez-Valera, F.; Bolhuis, H.; Dyall-Smith, M. L. (2007). "Haloquadratum walsbyi gen. nov., sp. nov., the square haloarchaeon of Walsby, isolated from saltern crystallizers in Australia and Spain". International Journal of Systematic and Evolutionary Microbiology. 57 (2): 387–392. doi: 10.1099/ijs.0.64690-0 . PMID   17267984.
  5. Oren A, Pri-El N, Shapiro O, Siboni N (2006). "Buoyancy studies in natural communities of square gas-vacuolate archaea in saltern crystallizer ponds". Saline Systems. 2: 4. doi: 10.1186/1746-1448-2-4 . PMC   1459177 . PMID   16613609.
  6. Information at J. Craig Venter Institute Archived 2014-02-23 at archive.today
  7. Dyall-Smith, M. L.; Pfeiffer, F.; Klee, K.; Palm, P.; Gross, K.; Schuster, S. C.; Rampp, M.; Oesterhelt, D. (2011). Lopez-Garcia, Purification (ed.). "Haloquadratum walsbyi : Limited Diversity in a Global Pond". PLOS ONE. 6 (6): e20968. Bibcode:2011PLoSO...620968D. doi: 10.1371/journal.pone.0020968 . PMC   3119063 . PMID   21701686.

Further reading