Haloarchaea

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Halobacteria (plural form of the word "halobacterium") redirects here. For the genus, see halobacterium.
Haloarchaea
Halobacteria.jpg
Halobacterium sp. strain NRC-1, each cell about 5 µm in length.
Scientific classification
Domain: Archaea
Kingdom: Archaea
Phylum: Euryarchaeota
Class: Halobacteria
Order
Synonyms
  • Halobacteria Grant et al. 2002

In taxonomy, the Halobacteria (also Halomebacteria) are a class of the Euryarchaeota,[1] found in water saturated or nearly saturated with salt. Halobacteria are now recognized as archaea, rather than bacteria. The name 'halobacteria' was assigned to this group of organisms before the existence of the domain Archaea was realized, and remains valid according to taxonomic rules[citation needed]. In a non-taxonomic context, halophilic archaea are referred to as haloarchaea to distinguish them from halophilic bacteria.

These microorganisms are members of the halophile community, in that they require high salt concentrations to grow. They are a distinct evolutionary branch of the Archaea, and are generally considered extremophiles, although not all members of this group can be considered as such.

Haloarchaea can grow aerobically or anaerobically. Parts of the membranes of haloarchaea are purplish in color, and large blooms of haloarchaea appear reddish, from the pigment bacteriorhodopsin, related to the retinal pigment rhodopsin which it uses as a source of energy by a process unrelated to other forms or photosynthesis.

Taxonomy[edit]

The extremely halophilic, aerobic members of Archaea are classified within the family Halobacteriaceae, order Halobacteriales in Class III. Halobacteria of the phylum Euryarchaeota (International Committee on Systematics of Prokaryotes, Subcommittee on the taxonomy of Halobacteriaceae). As of May 2015, the family Halobacteriaceae comprises 48 genera 191 species.

Domain : Archaea

Phylum: Euryarchaeota

  • Class: Halobacteria
    • Order: Halobacteriales
      • Family: Halobacteriaceae
        • Haladaptatus [Hap.]
          • Haladaptatus cibarius
          • Haladaptatus litoreus
          • Haladaptatus pallidirubidus
          • Haladaptatus paucihalophilus (Type species)
        • Halalkalicoccus [Hac.]
          • Halalkalicoccus jeotgali
          • Halalkalicoccus tibetensis (Type species)
          • Halalkalicoccus paucihalophilus
        • Halapricum [Hpr.]
          • Halapricum salinum (Type species)
        • Halarchaeum [Hla.]
          • Halarchaeum acidiphilum (Type species)
          • Halarchaeum nitratireducens
          • Halarchaeum rubridurum
          • Halarchaeum salinam
          • Halarchaeum solikamskense
        • Haloarchaeobius [Hab.]
          • Haloarchaeobius iranensis (Type species)
          • Haloarchaeobius litoreus
          • "Haloarchaeobius salinus" (IJSEM, in press)
        • Haloarcula [Har.]
          • Haloarcula amylolytica
          • Haloarcula argentinensis
          • Haloarcula hispanica
          • Haloarcula japonica
          • Haloarcula marismortui
          • Haloarcula quadrata
          • Haloarcula salaria
          • Haloarcula tradensis
          • Haloarcula vallismortis (Type species)
        • Halobacterium [Hbt.] (Type genus)
          • Halobacterium jilantaiense
          • Halobacterium noricense
          • "Halobacterium piscisalsi" (subjective junior synonym of Halobacterium salinarum)[2]
          • Halobacterium ruburm
          • Halobacterium salinarum (Type species)
        • Halobaculum [Hbl.]
          • Halobaculum gomorrense (Type species)
          • Halobaculum magnesiiphilum
        • Halobellus [Hbs.]
          • Halobellus clavatus (Type species)
          • Halobellus inordinatus
          • Halobellus limi
          • Halobellus litoreus
          • Halobellus salinus
          • Halobellus rarus
          • Halobellus rufus
        • Halobiforma [Hbf.]
          • Halobiforma haloterrestris (Type species)
          • Halobiforma lacisalsi
          • Halobiforma nitratireducens
        • "Halocalculus" [Hcl.]
          • "Halocalculus aciditolerans " (Type species) (IJSEM, in press)
        • Halococcus [Hcc.]
          • "Halococcus agarilyticus" (IJSEM, in press)
          • Halococcus dombrowskii
          • Halococcus hamelinensis
          • Halococcus morrhuae (Type species)
          • Halococcus qingdaonensis
          • Halococcus saccharolyticus
          • Halococcus salifodinae
          • Halococcus sediminicola
          • Halococcus thailandensis
        • Haloferax [Hfx.]
          • Haloferax alexandrinus
          • Haloferax chudinovii
          • Haloferax denitrificans
          • Haloferax elongans
          • Haloferax gibbonsii
          • Haloferax larsenii
          • Haloferax lucentense
          • Haloferax mediterranei
          • Haloferax mucosum
          • Haloferax prahovense
          • Haloferax sulfurifontis
          • Haloferax volcanii (Type species)
        • Halogeometricum [Hgm.][3]
          • Halogeometricum borinquense (Type species)
          • Halogeometricum limi
          • Halogeometricum pallidum
          • Halogeometricum rufum
        • Halogranum [Hgn.]
          • Halogranum amylolyticum
          • Halogranum gelatinilyticum
          • Halogranum rubrum (Type species)
          • Halogranum salarium
        • Halohasta [Hht.]
          • Halohasta litorea (Type species)
          • Halohasta litchfieldiae
        • Halolamina [Hlm.]
          • Halolamina pelagica (Type species)
          • Halolamina rubra
          • Halolamina salifodinae
          • Halolamina salina
          • "Halolamina sediminis" (IJSEM, in press)
        • Halomarina [Hmr.]
          • Halomarina oriensis (Type species)
        • Halomicroarcula [Hma.]
          • Halomicroarcula limicola
          • Halomicroarcula pellucida (Type species)
          • "Halomicroarcula salina" (IJSEM, in press)
        • Halomicrobium [Hmc.]
          • Halomicrobium katesii
          • Halomicrobium mukohataei (Type species)
          • Halomicrobium zhouii
        • Halonotius [Hns.]
          • Halonotius pteroides (Type species)
        • Halopelagius [Hpl.]
          • Halopelagius inordinatus (Type species)
          • Halopelagius fulvigenes
          • Halopelagius longus
        • Halopenitus [Hpt.]
          • Halopenitus salinus
          • Halopenitus malekzadehii
          • Halopenitus persicus (Type species)
        • Halopiger [Hpg.]
          • Halopiger aswanensis
          • Halopiger salifodinae
          • Halopiger xanaduensis (Type species)
        • Haloplanus [Hpn.]
          • Haloplanus aerogenes
          • Haloplanus litoreus
          • Haloplanus natans (Type species)
          • Haloplanus ruber
          • Haloplanus salinus
          • Haloplanus vescus
        • Haloquadratum [Hqr.]
          • Haloquadratum walsbyi (Type species)
        • Halorhabdus [Hrd.]
          • Halorhabdus tiamatea
          • Halorhabdus utahensis (Type species)
        • Halorientalis [Hos.]
          • Halorientalis persicus
          • Halorientalis regularis (Type species)
        • Halorubellus [Hrb.]
          • Halorubellus litoreus
          • Halorubellus salinus (Type species)
        • Halorubrum [Hrr.]
          • Halorubrum aquaticum
          • Halorubrum aidingense
          • Halorubrum alkaliphilum
          • Halorubrum arcis
          • Halorubrum californiense
          • Halorubrum chaoviator
          • Halorubrum cibi
          • Halorubrum coriense
          • Halorubrum distributum
          • Halorubrum ejinorense
          • Halorubrum ezzemoulense
          • Halorubrum halophilum
          • Halorubrum lacusprofundi
          • "Halorubrum laminariae" (Antonie Van Leeuwenhoek, 2015, 107:217-223)
          • Halorubrum lipolyticum
          • Halorubrum litoreum
          • Halorubrum luteum
          • Halorubrum orientale
          • "Halorubrum persicum" (IJSEM, in press)
          • Halorubrum rubrum
          • Halorubrum saccharovorum (Type species)
          • Halorubrum salinum
          • Halorubrum sodomense
          • Halorubrum tebenquichense
          • Halorubrum terrestre
          • Halorubrum tibetense
          • Halorubrum trapanicum
          • Halorubrum vacuolatum
          • Halorubrum xinjiangense
        • Halorussus [Hrs.]
          • Halorussus rarus
          • "Halorussus ruber" (Arch Microbiol, 2015, 197:91-95)
        • Halosimplex [Hsx.]
          • Halosimplex carlsbadense (Type species)
          • Halosimplex pelagicum
          • Halosimplex rubrum
        • Halostagnicola [Hst.]
          • Halostagnicola alkaliphila
          • Halostagnicola bangensis
          • Halostagnicola kamekurae
          • Halostagnicola larsenii (Type species)
        • Haloterrigena [Htg.]
          • Haloterrigena daqingensis
          • Haloterrigena hispanica
          • Haloterrigena jeotgali
          • Haloterrigena limicola
          • Haloterrigena longa
          • Haloterrigena saccharevitans
          • Haloterrigena salina
          • Haloterrigena thermotolerans
          • Haloterrigena turkmenica (Type species)
        • "Halovarius" ["Hvr".]
          • "Halovarius luteus" (Type species) (IJSEM, in press)
        • Halovenus [Hvn.]
          • Halovenus aranensis (Type species)
          • "Halovenus rubra" (Curr Microbiol, 2015, 70:91-95)
        • Halovivax [Hvx.]
          • Halovivax asiaticus (Type species)
          • "Halovivax limisalsi" (IJSEM, in press)
          • Halovivax ruber
        • Natrialba [Nab.]
          • Natrialba aegyptia
          • Natrialba asiatica (Type species)
          • Natrialba chahannaoensis
          • Natrialba hulunbeirensis
          • Natrialba magadii
          • Natrialba taiwanensis
        • Natribaculum [Nbl.]
          • Natribaculum breve (Type species)
          • Natribaculum longum
        • Natrinema [Nnm.]
          • Natrinema altunense
          • Natrinema ejinorense
          • Natrinema gari
          • Natrinema pallidum
          • Natrinema pellirubrum (Type species)
          • Natrinema salaciae
          • Natrinema versiforme
        • Natronoarchaeum [Nac.]
          • Natronoarchaeum mannanilyticum (Type species)
          • Natronoarchaeum philippinense
          • Natronoarchaeum rubrum
        • Natronobacterium [Nbt.]
          • Natronobacterium gregoryi (Type species)
          • Natronobacterium texcoconense
        • Natronococcus [Ncc.]
          • Natronococcus amylolyticus
          • Natronococcus jeotgali
          • Natronococcus occultus (Type species)
          • Natronococcus roseus
        • Natronolimnobius [Nln.]
          • Natronolimnobius baerhuensis (Type species)
          • Natronolimnobius innermongolicus
        • Natronomonas [Nmn.]
          • Natronomonas gomsonensis
          • Natronomonas moolapensis
          • Natronomonas pharaonis (Type species)
        • Natronorubrum [Nrr.]
          • Natronorubrum aibiense
          • Natronorubrum bangense (Type species)
          • Natronorubrum sediminis
          • Natronorubrum sulfidifaciens
          • Natronorubrum texcoconense
          • Natronorubrum tibetense
        • Salarchaeum [Sar.]
          • Salarchaeum japonicum (Type species)
        • Salinarchaeum [Saa.]
          • Salinarchaeum laminariae (Type species)
        • Salinigranum [Sgn.]
          • Salinigranum rubrum (Type species)
        • "Salinirubrum" ["Srr".]
          • Salinirubrum litoreum (Type species)

Living environment[edit]

Salt ponds with pink colored Haloarchaea

Haloarchaea require salt concentrations in excess of 2 M (or about 10%) to grow, and optimal growth usually occurs at much higher concentrations, typically 20–25%. However, Haloarchaea can grow up to saturation (about 37% salts).

Haloarchaea are found mainly in hypersaline lakes and solar salterns. Their high densities in the water often lead to pink or red colourations of the water (the cells possessing high levels of carotenoid pigments, presumably for UV protection).[4]

Photosynthesis in haloarchaea[edit]

Bacteriorhodopsin is used to absorb light, which provides energy to create ATP. Haloarchaea also possess a second pigment, halorhodopsin, which pumps chloride ions in the cell 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 haloarchaea are incapable of fixing carbon from carbon dioxide.[5]

Cellular shapes[edit]

Haloarchaea are often considered pleomorphic, or able to take on a range of shapes—even within the one species. This makes identification by microscopic means difficult, and it is now more common to use gene sequencing techniques for identification instead.

One of the more unusually shaped Haloarchaea is the "Square Haloarchaeon of Walsby." It was classified in 2004 using a very low nutrition solution to allow growth along with a high salt concentration, square in shape and extremely thin (like a postage stamp). This shape is probably only permitted by the high osmolarity of the water, permitting cell shapes that would be difficult, if not impossible, under other conditions.

Haloarchaea as Exophiles[edit]

Haloarchaea have been proposed as a kind of life that could live on Mars; since the Martian atmosphere has a pressure below the triple point of water, freshwater species would have no habitat on the Martian surface.[6]

See also[edit]

References[edit]

  1. ^ See the NCBI webpage on Halobacteria. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. Retrieved 2007-03-19. 
  2. ^ Minegishi, H., Echigo, A., Shimane, Y., Kamekura, M., Tanasupawat, S., Visessanguan, W., Usami, R. (2012) "Halobacterium piscisalsi Yachai et al. 2008 is later heterotypic synonym of Halobacterium salinarum Elazari-Volcani 1957." Int J Syst Evol Microbiol. 62: 2160-2162
  3. ^ Qiu, X.X., Zhao, M.L., Han, D., Zhang, W.J., Dyall-Smith, M.L., Cui, H.L. (2013) "Taxonomic study of the genera Halogeometricum and Halosarcina: transfer of Halosarcina limi and Halosarcina pallida to the genus Halogeometricum as Halogeometricum limi comb. nov. and Halogeometricum pallidum comb. nov., respectively." Int J Syst Evol Microbiol. 63: 3915-3919
  4. ^ DasSarma, Shiladitya (2007). "Extreme Microbes". American Scientist 95 (3): 224–231. doi:10.1511/2007.65.1024. ISSN 0003-0996. 
  5. ^ This paragraph taken directly from the Academic Dictionaries and Encyclopedias page on Halobacterium
  6. ^ DasSarma, Shiladitya. "Extreme Halophiles Are Models for Astrobiology" (PDF). Archived from the original (PDF) on 2007-02-02. Retrieved 2007-03-17. 

Further reading[edit]

Scientific journals[edit]

Scientific books[edit]

  • Grant WD, Kamekura M, McGenity TJ, Ventosa A (2001). "Class III. Halobacteria class. nov.". In DR Boone and RW Castenholz, eds. Bergey's Manual of Systematic Bacteriology Volume 1: The Archaea and the deeply branching and phototrophic Bacteria (2nd ed.). New York: Springer Verlag. p. 169. ISBN 978-0-387-98771-2. 
  • Garrity GM, Holt JG (2001). "Phylum AII. Euryarchaeota phy. nov.". In DR Boone and RW Castenholz, eds. Bergey's Manual of Systematic Bacteriology Volume 1: The Archaea and the deeply branching and phototrophic Bacteria (2nd ed.). New York: Springer Verlag. p. 169. ISBN 978-0-387-98771-2. 

Scientific databases[edit]

External links[edit]