Haloquadratum walsbyi: Difference between revisions
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==Genome structure== | ==Genome structure== | ||
Haloquadratum walsbyi was found to be a member of a novel genus within the family of Halobateriaceae, based on its 16S RNA sequence. The 3.1 Mb large genome has been sequenced and is discussed in "The genome of the square archaeon Haloquadratum walsbyi: life at the limits of water activity" by Bolhius et al | Haloquadratum walsbyi was found to be a member of a novel genus within the family of Halobateriaceae, based on its 16S RNA sequence. The 3.1 Mb large genome has been sequenced and is discussed in "The genome of the square archaeon Haloquadratum walsbyi: life at the limits of water activity" by Bolhius et al (2). | ||
The genome of | The genome of the Haloquadratum walsbyi strain studied by Bolhius is comprised of a 3,132,494 bp chromosome (which has 2738 open reading frames) and a 46,867 bp plasmid (which has 39 open reading frames). The genome has a well conserved haloarchael region, which contains the origin of replication and the cell division control protein CDC6_1. (2) | ||
Its genome has a GC content of 47.9%, which is remarkably low compared to the generally high GC content of other haloarchaea (usually 60-70%). This GC content is constant throughout the genome. It is thought that the lowered GC content is compensated by the large number of photolyases which help it cope with the high levels of UV irradiation which it encounters in the shallow coastal lagoons it inhabits. Although its GC content differs from most other haloarchaea, most of the typical haloarchael proteins that Haloquadratum walsbyi encodes were found to be highly conserved at the level of the amino acid sequence. (2) | |||
Notable about H.walsbyi's genome include the following: its low coding density at 75% (compared to the 86-91% of other haloarchaea), its expression of a water enriched capsule, the fact that it encodes two bacteriorhodopsin proteins, as well as its utilization of a dihydroxyacetone via phophoenolpyruvate dependent phosphotransferase system. (2) | |||
The 47 kb plasmid of H.walsbyi, which similarly has a constant GC distribution, contains many genes--many of which are “hypothetical or conserved hypothetical” (2). The majority of the identified genes encode proteins that are involved in the maintenance, replication, and restriction modification of the plasmid. Interestingly, most of these are found to be bacterial or viral (phage) descent instead of archaeal descent. (2) | |||
==Cell structure and metabolism== | ==Cell structure and metabolism== | ||
Revision as of 06:12, 6 June 2007
A Microbial Biorealm page on the genus Haloquadratum walsbyi
Classification
Higher order taxa
cellular organisms; Archaea; Euryarchaeota; Halobacteria; Halobacteriales; Halobacteriaceae; Haloquadratum; Haloquadratum walsbyi
(from NCBI
Genus
Haloquadratum
Description and significance
The square halophilic archaeon Haloquadratum walsbyi was first discovered by A.E. Walsby in 1980. First found in water from a salt pool near the Red Sea, Haloquadratum walsbyi was soon found in many salt lakes around the world, making it an archaeon of specific interest because of this abundance in hypersaline ecosystems, which suggests that is it plays an important ecological role. A.E. Walsby detected Haloquadratum walsbyi by "conventional microscopy in brine samples collected from a salt crust forming the surface of a hypersaline pool on the Sinai Peninsula" (1).
The cells of "Walsby's square archaeon" possess a unique square-like shape, unlike the spherical or cylindrical shape of many organisms. Easily recognizable for its perfect square morphology, Haloquadratum walsbyi has sharp edges and acute straight corners. (3)
Despite their abundance in salt lakes around the world, cultivation of Haloquadratum walsbyi has been very difficult, and it has been marked an unculturable organism. In "Isolation and cultivation of Walsby's square archaon," the first cultivation of the organism is discussed. (1)
It is important for this organism to be studied because of its halophilicity which suggests that Haloquadratum walsbyi plays an important ecological role in high-salt content habitats. The genome sequence gives insight in the molecular ecological & physiological properties of the organism, including its square shape and its ability to survive in the hypersaline environments it is found in and the high UV radiation it is exposed to. Additionally, studying the genome sequence might enable us to understand its metabolic properties which allow Haloquadratum walsbyi to live in such an environment and which initially made the organism difficult to cultivate. (2)
Genome structure
Haloquadratum walsbyi was found to be a member of a novel genus within the family of Halobateriaceae, based on its 16S RNA sequence. The 3.1 Mb large genome has been sequenced and is discussed in "The genome of the square archaeon Haloquadratum walsbyi: life at the limits of water activity" by Bolhius et al (2).
The genome of the Haloquadratum walsbyi strain studied by Bolhius is comprised of a 3,132,494 bp chromosome (which has 2738 open reading frames) and a 46,867 bp plasmid (which has 39 open reading frames). The genome has a well conserved haloarchael region, which contains the origin of replication and the cell division control protein CDC6_1. (2)
Its genome has a GC content of 47.9%, which is remarkably low compared to the generally high GC content of other haloarchaea (usually 60-70%). This GC content is constant throughout the genome. It is thought that the lowered GC content is compensated by the large number of photolyases which help it cope with the high levels of UV irradiation which it encounters in the shallow coastal lagoons it inhabits. Although its GC content differs from most other haloarchaea, most of the typical haloarchael proteins that Haloquadratum walsbyi encodes were found to be highly conserved at the level of the amino acid sequence. (2)
Notable about H.walsbyi's genome include the following: its low coding density at 75% (compared to the 86-91% of other haloarchaea), its expression of a water enriched capsule, the fact that it encodes two bacteriorhodopsin proteins, as well as its utilization of a dihydroxyacetone via phophoenolpyruvate dependent phosphotransferase system. (2)
The 47 kb plasmid of H.walsbyi, which similarly has a constant GC distribution, contains many genes--many of which are “hypothetical or conserved hypothetical” (2). The majority of the identified genes encode proteins that are involved in the maintenance, replication, and restriction modification of the plasmid. Interestingly, most of these are found to be bacterial or viral (phage) descent instead of archaeal descent. (2)
Cell structure and metabolism
Haloquadratum walsbyi have flat cells that have a unique square-like shape, unlike the spherical or cylindrical sahpe of many organisms. Easily recognizable for its perfect square morphology, Haloquadratum walsbyi has sharp edges and acute straight corners.
Another feature is the abundance of intracellular refractile bodies, which were identified as gas vesicles. These gas vesicles were also found to be easily collapsed by gentle pressure.
PHA storage granules have also been found.
NEED TO ADD: How it gains energy, What important molecules it produces
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
10. Walsby A. E. "A square bacterium" Nature 283, 69-71. 03 January 1980. doi:10.1038/283069a0
Edited by Heidi T. Tuason, student of Rachel Larsen and Kit Pogliano
