Haloferax
Encyclopedia
In taxonomy
, Haloferax is a genus of the Halobacteriaceae
.
Haloferax volcanii's genome has officially been completely sequenced, however it is not yet available in full in annotated form. The molecular biology of H. volcanii has been extensively studied for the last decade in order to discover more about DNA replication, DNA repair and RNA synthesis. The archaeal proteins used in these processes are extremely similar to Eukaryotic proteins and so are studied primarily as a model system for these organisms. Haloferax volcanii undergoes prolific horizontal gene transfer both with Archaea and, to a lesser extent, bacteria.
Cell Structure and Metabolism
Reproduction among Haloferax volcanii occurs asexually by binary fission. This practice is similar to that of other Archaea and, indeed, that of bacteria.
H. volcanii cells have no cell wall and, like many archaea, therefore use their exterior S-layer for structure. They are typically recognisable by their 'dished crisp' shape, but are somewhat pleiomorphic so may be seen in other shapes including coccoid. The membranes of this organism are made of the typical ether linked membrane lipids found solely in archaea and also contain a high level of carotenoids including lycopene, which gives them their distinctive red colour.
H. volcanii use a salt in method to maintain osmostasis, rather than the typical compatible solutes method seen in bacteria. This method involves the maintenance of a high degree of K+ ions in the cell to balance the Na+ ions outside. For this reason H. volcanii has a complex ion regulation system.
Due to the salt in method cytoplasmic proteins are structured to fold in the presence of high ionic concentrations. As such they typically have a large number of charged residues on the exterior section of the protein and very hydrophobic residues forming a core. This structure increases their stability in saline and even high temperature environments considerably, but comes at some loss of processivity compared to bacterial homologs.
H. volcanii respire as their sole source of ATP, unlike several other halobateriacae, such as Halobacterium salinarium they are incapable of photphosphorylation as they lack the necessary bacterioruberin.
Alpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
, Haloferax is a genus of the Halobacteriaceae
Halobacteriaceae
In taxonomy, the Halobacteriaceae are a family of the Halobacteriales in the domain Archaea.- Overview :Halobacteriaceae are found in water saturated or nearly saturated with salt. They are also called halophiles, though this name is also used for other organisms which live in somewhat less...
.
Description and Significance
Haloferax volcanii is a species of halophile which exists in extreme saline environments. Recently an isolate of this species was studied by researchers at University of California-Berkeley as part of a project on the survival of haloarchaea on Mars. Like other halophiles, Haloferax volcanii has been isolated in high-saline environments, most commonly the Dead Sea, the Great Salt Lake, and oceanic environments with high NaCl concentrates.Genome Structure
Haloferax volcanii's genome consists of a large (4 Mb), multicopy chromosome and several megaplasmids.Haloferax volcanii's genome has officially been completely sequenced, however it is not yet available in full in annotated form. The molecular biology of H. volcanii has been extensively studied for the last decade in order to discover more about DNA replication, DNA repair and RNA synthesis. The archaeal proteins used in these processes are extremely similar to Eukaryotic proteins and so are studied primarily as a model system for these organisms. Haloferax volcanii undergoes prolific horizontal gene transfer both with Archaea and, to a lesser extent, bacteria.
Cell Structure and Metabolism
Reproduction among Haloferax volcanii occurs asexually by binary fission. This practice is similar to that of other Archaea and, indeed, that of bacteria.
H. volcanii cells have no cell wall and, like many archaea, therefore use their exterior S-layer for structure. They are typically recognisable by their 'dished crisp' shape, but are somewhat pleiomorphic so may be seen in other shapes including coccoid. The membranes of this organism are made of the typical ether linked membrane lipids found solely in archaea and also contain a high level of carotenoids including lycopene, which gives them their distinctive red colour.
H. volcanii use a salt in method to maintain osmostasis, rather than the typical compatible solutes method seen in bacteria. This method involves the maintenance of a high degree of K+ ions in the cell to balance the Na+ ions outside. For this reason H. volcanii has a complex ion regulation system.
Due to the salt in method cytoplasmic proteins are structured to fold in the presence of high ionic concentrations. As such they typically have a large number of charged residues on the exterior section of the protein and very hydrophobic residues forming a core. This structure increases their stability in saline and even high temperature environments considerably, but comes at some loss of processivity compared to bacterial homologs.
H. volcanii respire as their sole source of ATP, unlike several other halobateriacae, such as Halobacterium salinarium they are incapable of photphosphorylation as they lack the necessary bacterioruberin.