Halobacterium

Halobacterium (common abbreviation Hbt.), from Ancient Greek ἅλς (háls), meaning "salt", and "bacterium", is a genus in the family Halobacteriaceae. The genus Halobacterium ("salt" or "ocean bacterium") consists of several species of Archaea with an aerobic metabolism which requires an environment with a high concentration of salt; many of their proteins will not function in low-salt environments. They grow on amino acids in their aerobic conditions. Their cell walls are also quite different from those of bacteria, as ordinary lipoprotein membranes fail in high salt concentrations. In shape, they may be either rods or cocci, and in color, either red or purple. They reproduce via binary fission (constriction), and are motile. Halobacterium grows best in a 42 °C environment. The genome of an unspecified Halobacterium species, sequenced by Shiladitya DasSarma, comprises 2,571,010 bp (base pairs) of DNA compiled into three circular strands: one large chromosome with 2,014,239 bp, and two smaller ones with 191,346 and 365,425 bp. This species, called Halobacterium sp. NRC-1, has been extensively used for postgenomic analysis. Halobacterium species can be found in the Great Salt Lake, the Dead Sea, Lake Magadi, and any other waters with high salt concentration.…

Halobacterium (common abbreviation Hbt.), from Ancient Greek ἅλς (háls), meaning "salt", and "bacterium", is a genus in the family Halobacteriaceae. The genus Halobacterium ("salt" or "ocean bacterium") consists of several species of Archaea with an aerobic metabolism which requires an environment with a high concentration of salt; many of their proteins will not function in low-salt environments. They grow on amino acids in their aerobic conditions. Their cell walls are also quite different from those of bacteria, as ordinary lipoprotein membranes fail in high salt concentrations. In shape, they may be either rods or cocci, and in color, either red or purple. They reproduce via binary fission (constriction), and are motile. Halobacterium grows best in a 42 °C environment. The genome of an unspecified Halobacterium species, sequenced by Shiladitya DasSarma, comprises 2,571,010 bp (base pairs) of DNA compiled into three circular strands: one large chromosome with 2,014,239 bp, and two smaller ones with 191,346 and 365,425 bp. This species, called Halobacterium sp. NRC-1, has been extensively used for postgenomic analysis. Halobacterium species can be found in the Great Salt Lake, the Dead Sea, Lake Magadi, and any other waters with high salt concentration. Purple Halobacterium species owe their color to bacteriorhodopsin, a light-sensitive membrane protein which acts as a proton pump, providing chemical energy with the proton gradient for the cell using light energy. The resulting proton gradient across the cell membrane is used to drive ATP synthase to generate adenosine triphosphate (ATP). Bacteriorhodopsin is very similar to rhodopsin, light-sensitive receptor proteins found in the retina of most animals. ==Species of Halobacterium== ===Phylogeny=== The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI). ===Synonyms=== Halobacterium cutirubrum > Halobacterium salinarum Halobacterium denitrificans > Haloferax denitrificans Halobacterium distributum > Halorubrum distributum Halobacterium halobium > Halobacterium salinarum Halobacterium lacusprofundi > Halorubrum lacusprofundi Halobacterium mediterranei > Haloferax mediterranei Halobacterium pharaonis > Natronomonas pharaonis Halobacterium piscisalsi > Halobacterium salinarum Halobacterium saccharovorum > Halorubrum saccharovorum Halobacterium sodomense > Halorubrum sodomense Halobacterium trapanicum > Halorubrum trapanicum Halobacterium vallismortis > Haloarcula vallismortis Halobacterium volcanii > Haloferax volcanii ===Genome repair=== In Halobacterium sp. NRC-1, homologs of the E. coli nucleotide excision repair genes uvrA, uvrB and uvrC are required tor the removal of UV induced DNA damages (in the absence of photoreactivating light). Investigation of DNA repair in this archaeal halobacterium has contributed to our understanding of the diversity and evolution of genomic DNA repair systems generally. ==Applications== ===Food Industry=== There is potential for Halobacterium species to be used in the food industry. Some examples of uses can include the production of Beta-Carotene, a pigment in halophilic bacteria that contributes to their red coloration, is used in the food industry as a natural food dye. Halophiles also produce degradative enzymes such as lipases, amylases, proteases, and xylanases that are used in various food processing methods. Notable applications of these enzymes include enhancing the fermentation process of salty foods, improving dough quality for the baking of breads, and contributing to the production of coffee. ===Bioremediation=== Many species of halophilic bacteria produce exopolysaccharides (EPS) which are used industrially as bioremediation agents. Biosurfactants are also released by many halophilic bacteria and these amphiphilic compounds have been used for soil remediation. Many halophiles are highly tolerant of heavy metals making them potentially useful in the bioremediation of xenobiotic compounds and heavy metals that are released into the environment from mining and metal plating. Halophiles contribute to the bioremediation of contaminants by converting xenobiotics into less toxic compounds. Some Halobacterium species have been shown to be effective in the bioremediation of pollutants including aliphatic hydrocarbons, such as those found in crude oil; and aromatic hydrocarbons such as 4-hydroxybenzoic acid, a contaminant in some high salinity industrial runoffs. ===Pharmaceuticals=== Some strains of Halobacterium, including Halobacterium salinarum, are being explored for medical applications of their radiation-resistance mechanisms. Bacterioruberin is a carotenoid pigment found in Halobacterium which decreases the bacteria's sensitivity to γ-radiation and UV radiation. It has been shown in knockout studies, that the absence of bacterioruberin increases the sensitivity of the bacterium to oxidative DNA-damaging agents. Hydrogen peroxide, for example, reacts with bacteroruberin which prevents the production of reactive oxygen species, and thus protects the bacterium by reducing the oxidative capacity of the DNA-damaging agent. H. salinarum also exhibits high intracellular concentrations of potassium chloride which has also been shown to confer radiation resistance. Halobacterium are also being explored for the pharmaceutical applications of bioactive compounds they produce, including anticancer agents, antimicrobial biosurfactancts, and antimicrobial metabolites. ==Recombination and mating== UV irradiation of Halobacterium sp. strain NRC-1 induces several gene products employed in homologous recombination. For instance, a homolog of the rad51/recA gene, which plays a key role in recombination, is induced 7-fold by UV. Homologous recombination may rescue stalled replication forks, and/or facilitate recombinational repair of DNA damage. In its natural habitat, homologous recombination is likely induced by the UV irradiation in sunlight. Halobacterium volcanii has a distinctive mating system in which cytoplasmic bridges between cells appear to be used for transfer of DNA from one cell to another. In wild populations of Halorubrum, genetic exchange and recombination occur frequently. This exchange may be a primitive form of sexual interaction, similar to the more well studied bacterial transformation that is also a process for transferring DNA between cells leading to homologous recombinational repair of DNA damage. ==Further reading== ===Scientific journals=== DasSarma, S., B.R. Berquist, J.A. Coker, P. DasSarma, J.A. Müller. 2006. Post-genomics of the model haloarchaeon Halobacterium sp. NRC-1. Saline Systems 2:3. ===Scientific books=== DasSarma, S. 2004. Genome sequence of an extremely halophilic archaeon, in Microbial Genomes, pp. 383–399, C.M. Fraser, T. Read, and K.E. Nelson (eds.), Humana Press, Inc., Totowa, NJ. Lynn Margulis, Karlene V.Schwartz, Five Kingdoms. An Illustrated Guide to the Phyla of Life on Earth (W.H.Freeman, San Francisco, 1982) pp. 36–37 ==References== ==External links== The Halobacterium Genome

Text derived from https://en.wikipedia.org/w/index.php?oldid=1370172950 under CC BY-SA 4.0; modifications have been made.