Haloquadratum

Taxobox
color = darkgray
name = "Haloquadratum"


domain = Archaea
phylum = Euryarchaeota
classis = Halobacteria
ordo = Halobacteriales
familia = Halobacteriaceae
genus = "Haloquadratum"
subdivision_ranks = Species
subdivision =
* "H. walsbyi"

* "uncultured Haloquadratum sp."

"Haloquadratum" (="salt square") is a genus of the "Halobacteriaceae". [See the NCBI [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=293431 webpage on Haloquadratum] . Data extracted from the cite web | url=ftp://ftp.ncbi.nih.gov/pub/taxonomy/ | title=NCBI taxonomy resources | publisher=National Center for Biotechnology Information | accessdate=2007-03-19] The first species to be identified in this group, "Haloquadratum walsbyi", is highly unusual since its cells are flat, rectangular boxes in shape. [cite journal |author=Stoeckenius W |title=Walsby's square bacterium: fine structure of an orthogonal procaryote |journal=J. Bacteriol. |volume=148 |issue=1 |pages=352–60 |year=1981 |pmid=7287626 |url=http://jb.asm.org/cgi/pmidlookup?view=long&pmid=7287626]

First discovered in 1980 by A.E. Walsby in the Gavish Sabkha, a coastal brine pool on the Sinai Peninsula in Egypt, this archaeon was not successfully cultured until 2004. While attempting to culture "Haloquadratum walsbyi", a new species, "Haloarcula quadra", was found. "Haloquadratum" are remarkable for their shape, motility, and relative abundance in halophilic environments.

The cells contain large numbers of refractile gas-filled vacuoles which provide buoyancy in a watery environment and may help to position the cells to maximise light-harvesting [ [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1459177 PubMed Central] ] . The cells may join with others to form fragile sheets as extensive as 40 microns. They also have one to several flagella, making them highly motile. [ [http://microbewiki.kenyon.edu/index.php/Haloquadra Microbewiki] ]

"Haloquadratum walsbyi" can be found anywhere in hypersaline waters. When sea water evaporates, high concentration and precipitation of calcium carbonate and calcium sulphate 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.

References

Further reading

cientific journals

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cientific books

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cientific databases

External links

* [http://www.biochem.mpg.de/en/rd/oesterhelt/web_page_list/Org_Hqwal/ Max Planck Institute of Biochemistry]