| 词条 | Haloquadratum walsbyi |
| 释义 |
| image = Haloquadratum walsbyi00.jpg | domain = Archaea | phylum = Euryarchaeota | classis = Halobacteria | ordo = Halobacteriales | familia = Halobacteriaceae | genus = Haloquadratum | species= H. walsbyi | binomial = Haloquadratum walsbyi | binomial_authority = Burns et al. 2007 }} Haloquadratum walsbyi is a species of archaea that was discovered in a brine pool in the Sinai peninsula of Egypt. It is noted for both its flat, square shaped cells, and its unusual ability to survive in aqueous environments with high concentrations of sodium chloride and magnesium chloride.[1][2] The species' name Haloquadratum literally translates as "salt square". Haloquadratum walsbyi is a species of phototrophic halophilic archaea, currently (30 June 2013) the only species of the genus Haloquadratum. It is very unusual in that it has perfectly square flat-shaped cells. These microorganisms were observed for the first time in 1980 by a British microbiologist, Prof. r Anthony E. Walsby, from samples taken from the Sabkha Gavish, a brine lake in southern Sinai , in Egypt , and has been described formally in 2007 by Burns et al. They are usually abundant in most salty environments. Attempts to cultivate them were unsuccessful until 2004 and resulted in the identification of Haloarcula quadrata , another species of square archaea of the genus Haloarcula , distinct from HQR. walsbyi , less abundant and genetically quite different. The cells are large {{En dash}} 2 to 5 microns {{En dash}} but very thin {{En dash}} approximately 150 nm {{En dash}} and generally contain granules of polyhydroxyalkanoates. They also hold a large number of refractive vacuoles filled with gas that ensure buoyancy in an aqueous environment, and may help to position the cells to maximize the reception of light. They can gather in sheets up to 40 μm wide, but the connections between the cells are fragile and can easily be broken. These organisms can be found in any stretch of very salty water. During the evaporation of seawater, calcium carbonate (CaCO3) and calcium sulfate (CaSO4) precipitate first, leading to a brine rich in sodium chloride NaCl. If evaporation continues, NaCl precipitates in the form of halite, leaving a brine rich in magnesium chloride (MgCl 2). HQR. walsbyi prospers during the final phase of the precipitation of halite, and can constitute 80% of the biomass of this medium. The genome of Hqr. walsbyi has been completely sequenced, allowing access to a better understanding of the classification phylogenetic and taxonomic this organization and its role in the ecosystem. A genomic comparison of Spanish and Australian isolates (strains HBSQ001 and C23T) strongly suggests a rapid global dispersion, as they are remarkably similar and have maintained the order of genes. Its growth in the laboratory was obtained in a medium with very high chloride concentrations (greater than 2 mol · L-1 of MgCl 2and greater than 3 mol · L -1of NaCl ), making this organism among the most haloresistant known. Its optimum growth temperature is 40° C. References1. ^{{cite journal |last=Oren |first=A. |author2=Ventosa, A. |author3=Gutierrez, M. C. |author4=Kamekura, M. |date=1 July 1999 |title=Haloarcula quadrata sp. nov., a square, motile archaeon isolated from a brine pool in Sinai (Egypt) |journal=International Journal of Systematic Bacteriology |volume=49 |issue=3 |pages=1149–1155 |doi=10.1099/00207713-49-3-1149 |pmid=10425773}} 2. ^{{cite journal |last=Bolhuis |first=Henk |last2=Palm |first2=Peter |last3=Wende |first3=Andy |last4=Falb |first4=Michaela |last5=Rampp |first5=Markus |last6=Rodriguez-Valera |first6=Francisco |last7=Pfeiffer |first7=Friedhelm |last8=Oesterhelt |first8=Dieter |date=2006-07-04 |title=The genome of the square archaeon Haloquadratum walsbyi : life at the limits of water activity |url=https://doi.org/10.1186/1471-2164-7-169 |journal=BMC Genomics |volume=7 |issue=1 |pages=169 |doi=10.1186/1471-2164-7-169 |issn=1471-2164}} Further reading
External links
2 : Halobacteria|Archaea described in 2007 |
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