Note: The word "halobacteria" is also the plural form of the word "halobacterium

Halobacterium

In taxonomy, Halobacterium is a genus of the Halobacteriaceae.The genus Halobacterium consists of several species of archaea with an aerobic metabolism which require an environment with a high concentration of salt; many of their proteins will not function in low-salt environments. They grow on...

". Halobacteria are now recognized as archaea

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

, rather than bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. The name 'halobacteria' was assigned to this group of organisms before the existence of the domain Archaea

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

 was realised, and remains valid according to taxonomic rules. In a non-taxonomic context, halophilic archaea are also sometimes referred to as haloarchaea

Haloarchaea

Haloarchaea are microrganisms and 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.-Living...

 to distinguish them from halophilic bacteria.

In taxonomy

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...

, the Halobacteria (also Halomebacteria) are a class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 of the Euryarchaeota

Euryarchaeota

In the taxonomy of microorganisms, the Euryarchaeota are a phylum of the Archaea.The Euryarchaeota include the methanogens, which produce methane and are often found in intestines, the halobacteria, which survive extreme concentrations of salt, and some extremely thermophilic aerobes and anaerobes...

, found in water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 saturated or nearly saturated with salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

. They are also called halophile

Halophile

Halophiles are extremophile organisms that thrive in environments with very high concentrations of salt. The name comes from the Greek for "salt-loving". While the term is perhaps most often applied to some halophiles classified into the Archaea domain, there are also bacterial halophiles and some...

s, 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.

Halobacteria can grow aerobically or anaerobically. Parts of the membrane

Biological membrane

A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

s of halobacteria are purplish in color, and large blooms of Halobacteria appear reddish, from the pigment bacteriorhodopsin

Bacteriorhodopsin

Bacteriorhodopsin is a protein used by Archaea, the most notable one being Halobacteria. It acts as a proton pump; that is, it captures light energy and uses it to move protons across the membrane out of the cell...

, related to the retina

Retina

The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

l pigment rhodopsin

Rhodopsin

Rhodopsin, also known as visual purple, is a biological pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G-protein coupled receptor family and are extremely sensitive to light,...

. This pigment is used to absorb light, which provides energy to create ATP

Adenosine triphosphate

Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

. Halobacteria also possess a second pigment, halorhodopsin

Halorhodopsin

Halorhodopsin is a light-driven ion pump, specific for chloride ions, and found in phylogenetically ancient archaea, known as halobacteria...

, 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

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 involving electron transport however, and halobacteria are incapable of fixing carbon

Carbon fixation

In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...

 from carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

.

Taxonomy

The extremely halophilic, aerobic members of Archaea are classified within the family Halobacteriaceae, order Halobacteriales in Class III. Halomebacteria of the phylum Euryarchaeota (International Committee on Systematics of Prokaryotes, Subcommittee on the taxonomy of Halobacteriaceae. Currently (September, 2010), the family Halobacteriaceae comprises 29 genera.

Domain : Archaea

Phylum: Euryarchaeota

• Class: Halomebacteria
  • Order: Halobacteriales
    • Family: Halobacteriaceae
      • Haladaptatus [Hap.]
        • Haladaptatus cibarius
        • Haladaptatus litoreus
        • Haladaptatus paucihalophilus (Type species)
      • Halalkalicoccus [Hac.]
        • Halalkalicoccus jeotgali
        • Halalkalicoccus tibetensis (Type species)
      • "Halarchaeum" [Hla.]
        • "Halarchaeum acidiphilum" (Type species) (IJSEM in press)
      • Haloarcula [Har.]
        • Haloarcula amylolytica
        • Haloarcula argentinensis
        • Haloarcula hispanica
        • Haloarcula japonica
        • Haloarcula marismortui
        • Haloarcula quadrata
        • "Haloarcula salaria" (IJSEM in press)
        • "Haloarcula tradensis" (IJSEM in press)
        • Haloarcula vallismortis (Type species)
      • Halobacterium [Hbt.] (Type genus)
        • Halobacterium jilantaiense
        • Halobacterium noricense
        • Halobacterium piscisalsi
        • Halobacterium salinarum (Type species)
      • Halobaculum [Hbl.]
        • Halobaculum gomorrense (Type species)
      • Halobiforma [Hbf.]
        • Halobiforma haloterrestris (Type species)
        • Halobiforma lacisalsi
        • Halobiforma nitratireducens
      • Halococcus [Hcc.]
        • Halococcus dombrowskii
        • Halococcus hamelinensis
        • Halococcus morrhuae (Type species)
        • Halococcus qingdaonensis
        • Halococcus saccharolyticus
        • Halococcus salifodinae
        • Halococcus thailandensis
      • Haloferax [Hfx.]
        • Haloferax alexandrinus
        • Haloferax denitrificans
        • Haloferax elongans
        • Haloferax gibbonsii
        • Haloferax larsenii
        • Haloferax lucentense
        • Haloferax mediterranei
        • Haloferax mucosum
        • Haloferax prahovense
        • Haloferax sulfurifontis
        • Haloferax volcanii (Type species)
      • Halogeometricum [Hgm.]
        • Halogeometricum borinquense (Type species)
        • "Halogeometricum rufum" (IJSEM in press)
      • Halogranum [Hgn.]
        • "Halogranum amylolyticum" (IJSEM in press)
        • "Halogranum gelatinilyticum" (IJSEM in press)
        • Halogranum rubrum (Type species)
      • "Halolamina" [Hlm.]
        • "Halolamina pelagica" (Type species) (IJSEM in press)
      • "Halomarina" [Hmr.]
        • "Halomarina oriensis" (Type species) (IJSEM in press)
      • Halomicrobium [Hmc.]
        • Halomicrobium katesii
        • Halomicrobium mukohataei (Type species)
      • "Halonotius" [Hns.]
        • "Halonotius pteroides" (Type species)
      • Halopelagius [Hpl.]
        • Halopelagius inordinatus (Type species)
      • Halopiger [Hpg.]
        • Halopiger aswanensis
        • Halopiger xanaduensis (Type species)
      • Haloplanus [Hpn.]
        • "Haloplanus aerogenes" (Type species) (IJSEM in press)
        • Haloplanus natans (Type species)
        • Haloplanus vescus
      • Haloquadratum [Hqr.]
        • Haloquadratum walsbyi (Type species)
      • Halorhabdus [Hrd.]
        • Halorhabdus tiamatea
        • Halorhabdus utahensis (Type species)
      • Halorubrum [Hrr.]
        • Halorubrum aidingense
        • Halorubrum alkaliphilum
        • "Halorubrum aquaticum" (IJSEM in press)
        • Halorubrum arcis
        • Halorubrum californiense
        • Halorubrum chaoviator
        • Halorubrum cibi
        • Halorubrum coriense
        • Halorubrum distributum
        • Halorubrum ejinorense
        • Halorubrum ezzemoulense
        • Halorubrum kocurii
        • Halorubrum lacusprofundi
        • Halorubrum lipolyticum
        • Halorubrum litoreum
        • Halorubrum luteum
        • Halorubrum orientale
        • Halorubrum saccharovorum (Type species)
        • Halorubrum sodomense
        • Halorubrum tebenquichense
        • Halorubrum terrestre
        • Halorubrum tibetense
        • Halorubrum trapanicum
        • Halorubrum vacuolatum
        • Halorubrum xinjiangense
      • "Halorussus" [Hrs.]
        • "Halorussus rarus" (Type species) (Extremophiles [Epub ahead of print])
      • Halosarcina [Hsn.]
        • "Halosarcina limi" (IJSEM in press)
        • Halosarcina pallida (Type species)
      • Halosimplex [Hsx.]
        • Halosimplex carlsbadense (Type species)
      • Halostagnicola [Hst.]
        • "Halostagnicola alkaliphila" (IJSEM in press)
        • "Halostagnicola kamekurae" (IJSEM in press)
        • Halostagnicola larsenii (Type species)
      • Haloterrigena [Htg.]
        • "Haloterrigena daqingensis" (IJSEM in press)
        • Haloterrigena hispanica
        • Haloterrigena jeotgali
        • Haloterrigena limicola
        • Haloterrigena longa
        • Haloterrigena saccharevitans
        • Haloterrigena salina
        • Haloterrigena thermotolerans
        • Haloterrigena turkmenica (Type species)
      • Halovivax [Hvx.]
        • Halovivax asiaticus (Type species)
        • Halovivax ruber
      • Natrialba [Nab.]
        • Natrialba aegyptia
        • Natrialba asiatica (Type species)
        • Natrialba chahannaoensis
        • Natrialba hulunbeirensis
        • Natrialba magadii
        • Natrialba taiwanensis
      • Natrinema [Nnm.]
        • Natrinema altunense
        • Natrinema ejinorense
        • Natrinema gari
        • Natrinema pallidum
        • Natrinema pellirubrum (Type species)
        • Natrinema versiforme
      • "Natronoarchaeum" [Nac.]
        • "Natronoarchaeum mannanilyticum" (Type species) (IJSEM in press)
      • Natronobacterium [Nbt.]
        • Natronobacterium gregoryi (Type species)
      • Natronococcus [Ncc.]
        • Natronococcus amylolyticus
        • Natronococcus jeotgali
        • Natronococcus occultus (Type species)
      • Natronolimnobius [Nln.]
        • Natronolimnobius baerhuensis (Type species)
        • Natronolimnobius innermongolicus
      • Natronomonas [Nmn.]
        • "Natronomonas moolapensis"
        • Natronomonas pharaonis (Type species)
      • Natronorubrum [Nrr.]
        • Natronorubrum aibiense
        • Natronorubrum bangense (Type species)
        • Natronorubrum sediminis
        • Natronorubrum sulfidifaciens
        • Natronorubrum tibetense
      • "Salarchaeum" 属 [Sar.]
        • "Salarchaeum japonicum" (Type species) (IJSEM in press)

External links