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In taxonomy, the Halobacteriaceae are a family of the Halobacteriales in the domain Archaea. Halobacteriaceae represent a large part of halophilic Archaea, along with members in two other methanogenic families, Methanosarcinaceae and Methanocalculaceae. The family consists of many diverse genera that can survive extreme environmental niches. Most commonly, Halobacteriaceae are found in hypersaline lakes and can even tolerate sites polluted by heavy metals. They include neutrophiles, acidophiles, alkaliphiles, and there have even been psychrotolerant species discovered. Some members have been known to live aerobically, as well as anaerobically, and they come in many different morphologies. These diverse morphologies include rods in genus Halobacterium, cocci in Halococcus, flattened discs or cups in Haloferax, and other shapes ranging from flattened triangles in Haloarcula to squares in Haloquadratum, and Natronorubrum. Most species of Halobacteriaceae are best known for their high salt tolerance and red-pink pigmented members, but there are also non-pigmented species and those that require moderate salt conditions. Some species of Halobacteriaceae have been shown to exhibit phosphorus solubilizing activities that contribute to phosphorus cycling in hypersaline environments. Techniques such as 16S rRNA analysis and DNA-DNA hybridization have been major contributors to taxonomic classification in Halobacteriaceae, partly due to the difficulty in culturing halophilic Archaea.
In taxonomy, the Halobacteriales are an order of the Halobacteria, 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 concentrated salt water. They are common in most environments where large amounts of salt, moisture, and organic material are available. Large blooms appear reddish, from the pigment bacteriorhodopsin. This pigment is used to absorb light, which provides energy to create ATP. Halobacteria also possess a second pigment, halorhodopsin, which pumps in chloride ions in response to photons, creating a voltage gradient and assisting in the production of energy from light. The process is unrelated to other forms of photosynthesis involving electron transport; however, and halobacteria are incapable of fixing carbon from carbon dioxide.
Haloarchaea are a class of the Euryarchaeota, found in water saturated or nearly saturated with salt. Halobacteria are now recognized as archaea, rather than bacteria and are one of the largest groups. The name 'halobacteria' was assigned to this group of organisms before the existence of the domain Archaea was realized, and while valid according to taxonomic rules, should be updated. Halophilic archaea are generally referred to as haloarchaea to distinguish them from halophilic bacteria.
Halobaculum gomorrense is a rod-shaped extremely halophilic archaeon first isolated from the Dead Sea.
Halococcus dombrowskii is an archaeon first isolated from a Permian alpine salt deposit. It is an extremely halophilic coccoid with type strain H4T.
Thioalkalivibrio paradoxus is an alkaliphilic and obligately autotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes. Its type strain is ARh 1.
Colwellia demingiae is a psychrophilic Antarctic bacterial species with the ability to synthesize docosahexaenoic acid. It is nonpigmented, curved-rod-like in shape, exhibiting facultative anaerobic growth, and possessing an absolute requirement for sea water. Its type strain is ACAM 459T. This bacteria is named after Jody Deming, a professor and researcher at University of Washington and her research mentor, Rita Colwell.
Colwellia hornerae is a psychrophilic Antarctic bacterial species with the ability to synthesize docosahexaenoic acid. It is nonpigmented, curved-rod-like in shape, exhibiting facultative anaerobic growth and possessing an absolute requirement for sea water. Its type strain is ACAM 607T.
Colwellia rossensis is a psychrophilic Antarctic bacterial species with the ability to synthesize docosahexaenoic acid. It is non-pigmented, curved rod-like shaped, exhibiting facultative anaerobic growth and possessing an absolute requirement for sea water. Its type strain is ACAM 608T.
Colwellia psychrotropica is a psychrophilic Antarctic bacterial species with the ability to synthesize docosahexaenoic acid. It is nonpigmented, curved-rod-like in shape, exhibiting facultative anaerobic growth and possessing an absolute requirement for sea water. Its type strain is ACAM 179T.
Halobacterium noricense is a halophilic, rod-shaped microorganism that thrives in environments with salt levels near saturation. Despite the implication of the name, Halobacterium is actually a genus of archaea, not bacteria. H. noricense can be isolated from environments with high salinity such as the Dead Sea and the Great Salt Lake in Utah. Members of the Halobacterium genus are excellent model organisms for DNA replication and transcription due to the stability of their proteins and polymerases when exposed to high temperatures. To be classified in the genus Halobacterium, a microorganism must exhibit a membrane composition consisting of ether-linked phosphoglycerides and glycolipids.
Halomonas alimentaria is a bacterium first isolated from jeotgal, a traditional Korean fermented seafood, hence its name. It is Gram-negative, moderately halophilic, non-motile and coccus- or short rod-shaped, with type strain YKJ-16T.
Lentibacillus juripiscarius is an aerobic, spore-forming, Gram-positive, moderately halophilic bacteria, with type strain IS40-3T.
Methylocystis rosea is a methanotrophic, Gram-negative, rod-shaped, non-spore-forming and non-motile bacterium species from the genus of Methylocystis which has been isolated from arctic wetland soil on the Svalbard Islands in Norway.
Nocardiopsis alkaliphila is an alkaliphilic bacterium from the genus of Nocardiopsis which has been isolated from soil from Egypt. Nocardiopsis alkaliphila produces nocardiopyrone A, nocardiopyrone B and pyridinols.
Nocardiopsis salina is a halophilic bacterium from the genus of Nocardiopsis which has been isolated from hypersaline soil in the Xinjiang Province in China.
Hymenobacter is a Gram-negative and non-motile bacterial genus from the family Hymenobacteraceae.
Pontibacter korlensis is a Gram-negative and rod-shaped bacterium from the genus of Pontibacter which has been isolated from the desert of Xinjiang in China.
Pseudooceanicola antarcticus is a Gram-negative, aerobic, moderately halophilic and rod-shaped bacterium from the genus of Pseudooceanicola which has been isolated from seawater.
Natranaerobius thermophilus is a thermophilic, obligately anaerobic and halophilic bacterium from the genus of Natranaerobius which has been isolated from the Wadi An Natrun lake in Egypt.
References
- ↑ Hezayen, F. F. (2002). "Characterization of a novel halophilic archaeon, Halobiforma haloterrestris gen. nov., sp. nov., and transfer of Natronobacterium nitratireducens to Halobiforma nitratireducens comb. nov". International Journal of Systematic and Evolutionary Microbiology. 52 (6): 2271–2280. doi:10.1099/ijs.0.02324-0. ISSN 1466-5026. PMID 12508897.
