In
taxonomy
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
, the Halobacteriaceae are a
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of the
Halobacteriales
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 concentrate ...
in the domain
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
.
[See the ]NCBI
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...
br>webpage on Halobacteriaceae
Data extracted from the ''Halobacteriaceae'' represent a large part of
halophilic
The halophiles, named after the Greek word for "salt-loving", are extremophiles that thrive in high salt concentrations. While most halophiles are classified into the domain Archaea, there are also bacterial halophiles and some eukaryotic species, ...
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
neutrophile
A neutrophile is a neutrophilic organism that thrives in a neutral pH environment between 6.5 and 7.5.
Environment
The pH of the environment can support growth or hinder neutrophilic organisms. When the pH is within the microbe's range, they g ...
s,
acidophile
Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 5.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,Becker, A.Types of Bacteria ...
s (ex. ''Halarchaeum acidiphilum''),
alkaliphile Alkaliphiles are a class of extremophilic microbes capable of survival in alkaline ( pH roughly 8.5–11) environments, growing optimally around a pH of 10. These bacteria can be further categorized as obligate alkaliphiles (those that require high ...
s (ex. ''
Natronobacterium
In taxonomy, ''Natronobacterium'' is a genus of the Natrialbaceae.See the NCBIbr>webpage on Natronobacterium Data extracted from the A member of the domain Archaea, it is both an extreme halophile and alkaliphile, thriving at an optimum salin ...
''), and there have even been
psychrotolerant
Psychrophiles or cryophiles (adj. ''psychrophilic'' or ''cryophilic'') are extremophile, extremophilic organisms that are capable of cell growth, growth and reproduction in low temperatures, ranging from to . They have an optimal growth temperat ...
species discovered (ex.
''Hrr. lacusprofundi'').
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
''Halobacterium'' (common abbreviation ''Hbt.'') 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 ...
, cocci in
Halococcus
''Halococcus'' (common abbreviation: ''Hcc.'') is a genus (biology), genus of the Halococcaceae.
Ecology
''Halococcus'' is a genus of extreme halophilic archaea, meaning that they require high salt levels, sometimes as high as 32% NaCl, for o ...
, flattened discs or cups in
Haloferax
In taxonomy, ''Haloferax'' (common abbreviation: ''Hfx.'') is a genus of the Haloferacaceae.
Genetic exchange
Cells of ''H. mediterranei'' and cells of the related species '' H. volcanii'' can undergo a process of genetic exchange between two c ...
, and other shapes ranging from flattened triangles in
Haloarcula
''Haloarcula'' (common abbreviation ''Har.'') is a genus of extreme halophilic Archaea in the class of Halobactaria.
Cell Structure
''Haloarcula'' species can be distinguished from other genera in the family Halobacteriaceae by the presence of ...
to squares in
Haloquadratum
''Haloquadratum'' (common abbreviation: ''Hqr.'') is a genus of archaean, belonging to the family Haloferacaceae. The first species to be identified in this group, ''Haloquadratum walsbyi'', is unusual in that its cells are shaped like square, f ...
, and
Natronorubrum
''Natronorubrum'' is a genus in the family Halobacteriaceae.See the NCBI
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Healt ...
.
Most species of Halobacteriaceae are best known for their high salt tolerance and red-pink pigmented members (due to bacterioruberin carotenoids
), 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.
Overview
Halobacteriaceae are found in water saturated or nearly saturated with salt. They are also called
halophile
The halophiles, named after the Greek word for "salt-loving", are extremophiles that thrive in high salt concentrations. While most halophiles are classified into the domain Archaea, there are also bacterial halophiles and some eukaryotic species, ...
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. Large blooms appear reddish, from the pigment
bacteriorhodopsin
Bacteriorhodopsin is a protein used by Archaea, most notably by haloarchaea, a class of the Euryarchaeota. 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. The resulting ...
. This pigment is used to absorb light, which provides energy to create
ATP. Halobacteria also possess a second pigment,
halorhodopsin Halorhodopsin is a light-gated ion pump, specific for chloride ions, found in archaea, known as halobacteria. It is a seven-transmembrane retinylidene protein from microbial rhodopsin family. It is similar in tertiary structure (but not primary seq ...
, 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
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
involving electron transport and halobacteria are incapable of
fixing carbon from
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
.
Halobacteria can exist in salty environments because although they are
aerobes, they have a separate and different way of creating energy through use of light energy. Parts of the
membrane
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. B ...
s of halobacteria are purplish in color and contain retinal
pigment
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...
. This allows them to create a
proton gradient
An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and th ...
across the membrane of the cell which can be used to create
ATP for their own use.
They have certain adaptations to live within their salty environments. For example, their cellular machinery is adapted to high salt concentrations by having charged amino acids on their surfaces, allowing the cell to keep its water molecules around these components. The osmotic pressure and these amino acids help to control the amount of salt within the cell. However, because of these adaptations, if the cell is placed in a wet, less salty environment, it is likely to immediately burst from the osmotic pressure.
Phylogeny
The currently accepted taxonomy is based on the
List of Prokaryotic names with Standing in Nomenclature
List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature ...
(LPSN) and
National Center for Biotechnology Information
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...
(NCBI)
and the phylogeny is based on 16S rRNA-based LTP release 106 by
'The All-Species Living Tree' Project
The All-Species Living Tree' Project is a collaboration between various academic groups/institutes, such as ARB Project, ARB, SILVA rRNA database project, and List of Prokaryotic names with Standing in Nomenclature, LPSN, with the aim of assembli ...
.
'The All-Species Living Tree' Project
The All-Species Living Tree' Project is a collaboration between various academic groups/institutes, such as ARB Project, ARB, SILVA rRNA database project, and List of Prokaryotic names with Standing in Nomenclature, LPSN, with the aim of assembli ...
.
Notes:
♠ Strains found at the
National Center for Biotechnology Information
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...
(NCBI) but not listed in the
List of Prokaryotic names with Standing in Nomenclature
List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature ...
(LPSN)
♣
International Journal of Systematic Bacteriology
The ''International Journal of Systematic and Evolutionary Microbiology'' is a peer-reviewed scientific journal covering research in the field of microbial systematics that was established in 1951. Its scope covers the taxonomy, nomenclature, ...
or
(IJSB/IJSEM) published species that are in press.
References
Further reading
Scientific journals
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Scientific books
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Scientific databases
External links
Correct names of taxa within the family ''Halobacteriaceae''
{{Taxonbar, from=Q764133
Archaea taxonomic families
Euryarchaeota