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Encyclopedia > Archaea
Archaea
Fossil range: Archean - Recent
Halobacteria sp. strain NRC-1, each cell about 5 μm in length.
Halobacteria sp. strain NRC-1, each cell about 5 μm in length.
Scientific classification
Superdomain: Neomura
Domain: Archaea
Woese, Kandler & Wheelis, 1990
Phyla

Crenarchaeota
Euryarchaeota
Korarchaeota
Nanoarchaeota
ARMAN The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... Image File history File links No higher resolution available. ... Genera Haloarcula Halobacterium Halobaculum Halococcus Haloferax Halogeometricum Halorubrum Haloterrigena Natrialba Natrinema Natronobacterium Natronococcus Natronomonas Natronorubrum The halobacteria are a family of archaea, found in water saturated or nearly saturated with salt. ... For other uses, see Scientific classification (disambiguation). ... Domains Domain Archaea Domain Eukaryota Neomura is the hypothetical ancestor of the two domains of Archaea and Eukaryota. ... Carl Richard Woese (born July 15, 1928, Syracuse, New York) is an American microbiologist famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. ... Orders Caldisphaerales Cenarchaeales Desulfurococcales Sulfolobales Thermoproteales The Crenarchaeota are a major group of Archaea, containing many extremely thermophilic and psychrophilic organisms. ... Classes Archaeoglobi Halobacteria Methanobacteria Methanococci Methanomicrobia Methanopyri Thermococci Thermoplasmata The Euryarchaeota are a major group of Archaea. ... The Korarchaeota are a group of Archaea known only from 16S rRNA gene sequences obtained from samples of high temperature hydrothermal environments. ... Nanoarchaeum equitans is a species of tiny microbe, discovered in 2002 in a hot vent off the coast of Iceland by Karl Stetter. ... Archaeal Richmond Mine Acidophilic Nanoorganisms (ARMAN) were first discovered in an extremely acidic mine located in northern California (Iron Mountain Mine) by Baker et al in Jillian F. Banfields laboratory at the University of California Berkeley. ...

The Archaea (pronounced /ɑrˈkiːə/) are a group of prokaryotic and single-celled microorganisms. In this they are similar to bacteria but these two groups evolved differently, and are classified as different domains in the three-domain system. Originally these organisms were named archaebacteria. However, this term has not been favored since the three-domain system became popular. Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... In biology, a domain (also superregnum, superkingdom, or empire) is the top-level grouping of organisms in scientific classification, higher than a kingdom. ... The three-domain system is a biological classification introduced by Carl Woese in 1990 that emphasizes his separation of prokaryotes into two groups, originally called Eubacteria and Archaebacteria. ...


Although there is still uncertainty in the phylogeny, Archaea, Eukaryota and Bacteria were introduced as the fundamental classifications in the three-domain system by Carl Woese in 1977. As prokaryotes, archaea are also classified in kingdom Monera in the traditional five-kingdom Linnaean taxonomy. While their prokaryotic cell structure is similar to Bacteria, the genes of Archaea and several of their metabolic pathways are more closely related to those of eukaryotes. One way to account for this is to group archaeans and eukaryotes together in the clade Neomura, which might have arisen from gram-positive bacteria. On the other hand, other studies have suggested that Archaea may instead be the most ancient lineage in the world, with bacteria and eukaryotes diverging from this group.[1] In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Carl Richard Woese (born July 15, 1928, Syracuse, New York) is an American microbiologist famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. ... Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... In biological taxonomy, a kingdom or regnum is a taxon in either (historically) the highest rank, or (in the new three-domain system) the rank below domain. ... Figure 1. ... Title page of Systema Naturae, 10th edition, 1758. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... Domains Domain Archaea Domain Eukaryota Neomura is the hypothetical ancestor of the two domains of Archaea and Eukaryota. ... Gram-positive bacteria are those that are stained dark blue or violet by gram staining, in contrast to gram-negative bacteria, which are not affected by the stain. ...


Archaea were originally described in extreme environments, but have since been found in all habitats and may contribute up to 20% of total biomass.[2] These cells are particularly common in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet.[3] A single individual or species from this domain is called an archaeon (sometimes spelled "archeon"),[4] while the adjectival form is archaeal or archaean. The etymology is Greek, from αρχαία meaning "ancient things". An extremophile is an organism, usually unicellular, which thrives in or requires extreme conditions that would exceed optimal conditions for growth and reproduction in the majority of mesophilic terrestrial organisms. ... Look up habitat in Wiktionary, the free dictionary. ... For the eco-industrial use of the term, which includes dead material used for biofuels, see biomass An Antarctic krill, whose species comprises roughly 0. ... For the SpongeBob SquarePants character, see Plankton (SpongeBob SquarePants). ... In grammar, an adjective is a word whose main syntactic role is to modify a noun or pronoun (called the adjectives subject), giving more information about what the noun or pronoun refers to. ... Etymologies redirects here. ...

Contents

Microbiology

Further information: Microbiology

Early in the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their biochemistry, morphology and metabolism. For example, microbiologists tried to classify microorganisms based on the substances they consume, their shapes, and the structures of their cell walls.[5] However, a new approach was proposed in 1965,[6] and microbiologists began to examine the sequences of the genes in these organisms and use this genetic information to work out which prokaryotes are genuinely related to each other: this is known as phylogenetics. An agar plate streaked with microorganisms Microbiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. ... Biochemistry (from Greek: , bios, life and Egyptian kēme, earth[1]) is the study of the chemical processes in living organisms. ... The term morphology in biology refers to the outward appearance (shape, structure, colour, pattern) of an organism or taxon and its component parts. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... Plant cells separated by transparent cell walls. ... For other uses, see Gene (disambiguation). ... Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. ...

Archaea were first detected in extreme environments, such as volcanic hot springs.
Archaea were first detected in extreme environments, such as volcanic hot springs.

Archaea were identified as a separate group of prokaryotes in 1977 by Carl Woese and George E. Fox due to their separation from other prokaryotes in phylogenetic trees that were based on the sequences of ribosomal RNA (rRNA) genes.[7] These two groups were originally named the Archaebacteria and Eubacteria and treated as kingdoms or subkingdoms, which Woese and Fox termed Urkingdoms. Woese argued that this group of prokaryotes represented a fundamentally different branch of living things. He later renamed the two groups of prokaryotes Archaea and Bacteria to emphasize this, and argued that together with Eukarya they compose three Domains of living organisms.[8] At first, only the methanogens were placed in this new domain, but gradually microbiologists realized that the archaea are a large and diverse group of organisms. Image File history File links Aerial view of Grand Prismatic Spring, Yellowstone National Park Image by NPS Photo - http://www. ... Image File history File links Aerial view of Grand Prismatic Spring, Yellowstone National Park Image by NPS Photo - http://www. ... Green Dragon Spring at Norris Geyser A hot spring is a place where warm or hot groundwater issues from the ground on a regular basis for at least a predictable part of the year, and is significantly above the ambient ground temperature (which is usually around 55~57 F or... Carl Richard Woese (born July 15, 1928, Syracuse, New York) is an American microbiologist famous for defining the Archaea (a new domain or kingdom of life) in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. ... Professor George Edward Fox (born 1945) is a researcher at The University of Houston. ... Fig. ... Ribosomal RNA (rRNA), a type of RNA synthesized in the nucleolus by RNA Pol I, is the central component of the ribosome, the protein manufacturing machinery of all living cells. ... In biological taxonomy, a kingdom or regnum is a taxon in either (historically) the highest rank, or (in the new three-domain system) the rank below domain. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Kingdoms Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... The three-domain system is a biological classification introduced by Carl Woese in 1990 that emphasizes his separation of prokaryotes into two groups, originally called Eubacteria and Archaebacteria. ... Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. ...


Initially, archaea were thought of as extremophiles that existed only in apparently-inhospitable habitats, such as hot springs and salt lakes, but in the late 20th century it became increasingly clear that archaea are in fact widely distributed in nature and are common inhabitants of much less extreme habitats, such as soils and oceans.[9] This new appreciation of the importance and ubiquity of archaea came mostly from the increasing application of molecular biology techniques that could detect prokaryotes in samples of water or soil from their nucleic acids alone, avoiding the need to find ways to culture the organisms in the laboratory.[10][11] Green Dragon Spring at Norris Geyser A hot spring is a place where warm or hot groundwater issues from the ground on a regular basis for at least a predictable part of the year, and is significantly above the ambient ground temperature (which is usually around 55~57 F or... For a lake containing a high concentration of salt, see salt lake (geography). ... Molecular biology is the study of biology at a molecular level. ... Look up nucleic acid in Wiktionary, the free dictionary. ...


Origin and early evolution

Further information: Timeline of evolution

The Archaea should not be confused with the geological term Archean eon, also known as the Archeozoic era. This refers to the primordial period of earth history when prokaryotes were the only cellular organisms living on the planet.[12][13] Probable fossils of these ancient cells have been dated to almost 3.5 billion years ago,[14] and the remains of lipids that may be either archaean or eukaryotic have been detected in shales dating from 2.7 billion years ago.[15] Life on Earth  â€¢  â€¢  | Axis scale: millions of years ago. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. ... The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... This article is about Earth as a planet. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... A fossil Ammonite Fossils are the mineralized remains of animals or plants or other traces such as footprints. ...

Phylogenetic tree showing the relationship between the archaea and other forms of life.[16] Eukaryotes are colored red, archaea green and bacteria blue.

Woese argued that the bacteria, archaea, and eukaryotes each represent a primary line of descent that diverged early on from an ancestral progenote with poorly developed genetic machinery.[17] Later he treated these groups formally as domains, each comprising several kingdoms. This division has become very popular, although the idea of the progenote itself is not generally supported. Some biologists, however, have argued that the archaebacteria and eukaryotes arose from specialized eubacteria.[18] One possibility is that last common ancestor of the bacteria and archaea may have been a non-methanogenic thermophile, which raises the possibility that lower temperatures are extreme environments in archaeal terms, and organisms that can survive in cooler environments appeared later in the evolution of these organisms.[19] Image File history File links Size of this preview: 800 × 528 pixelsFull resolution (1122 × 741 pixel, file size: 123 KB, MIME type: image/png) A highly resolved Tree Of Life, based on completely sequenced genomes [1]. The image was generated using iTOL: Interactive Tree Of Life[2], an online phylogenetic... Image File history File links Size of this preview: 800 × 528 pixelsFull resolution (1122 × 741 pixel, file size: 123 KB, MIME type: image/png) A highly resolved Tree Of Life, based on completely sequenced genomes [1]. The image was generated using iTOL: Interactive Tree Of Life[2], an online phylogenetic... Fig. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... The three-domain system is a biological classification introduced by Carl Woese in 1990 that emphasizes his separation of prokaryotes into two groups, originally called Eubacteria and Archaebacteria. ...


The relationship between archaea and eukaryotes remains an important problem. Aside from the similarities noted above, many genetic trees group the two together, with some analyses even suggesting that eukaryotes have a closer relationship to the archaeal phylum Euryarchaeota than the relationship between the Euryarchaeota and the phylum Crenarchaeota: although the shared similarities in the cell structure of the archaea might suggest otherwise. However, the discovery of archaean-like genes in certain bacteria, such as Thermotoga maritima, makes these relationships difficult to determine, as horizontal gene transfer has occurred.[20] Classes Archaeoglobi Halobacteria Methanobacteria Methanococci Methanomicrobia Methanopyri Thermococci Thermoplasmata The Euryarchaeota are a major group of Archaea. ... Orders Caldisphaerales Cenarchaeales Desulfurococcales Sulfolobales Thermoproteales The Crenarchaeota are a major group of Archaea, containing many extremely thermophilic and psychrophilic organisms. ... Species Thermotoga elfii Thermotoga hypogea Thermotoga lettingae Thermotoga maritima Thermotoga naphthophila Thermotoga neapolitana Thermotoga petrophila Thermotoga subterranea Thermotoga thermarum Thermotoga are thermophile or hyperthermophile bacteria whose cell is wrapped in an outer toga membrane. ... Horizontal gene transfer (HGT), also Lateral gene transfer (LGT), is any process in which an organism transfers genetic material to another cell that is not its offspring. ...


Some have suggested that eukaryotes arose through fusion of an archaean and eubacterium, which became the nucleus and cytoplasm, which accounts for various genetic similarities but runs into difficulties explaining cell structure.[21] However, a recent large scale phylogenetic analysis of the structure of proteins encoded in almost 200 completely sequenced genomes showed that the origin of Archaea is much more ancient and that the archaeal lineage may represent the most ancient that exists on earth.[1] In fact, the study shows that the ancestor of all life had a proteome with a rather complex collection of protein structures, many of which are widely spread in modern metabolism. Single gene sequencing for systematics has led to whole genome sequencing; by March, 2008, 49 archaeal genomes have been completed with 34 in progress.[22] In genetics and biochemistry, sequencing means to determine the primary structure (or primary sequence) of an unbranched biopolymer. ... Biological systematics is the study of the diversity of life on the planet earth, both past and present, and the relationships among living things through time. ... In genetics and biochemistry, sequencing means to determine the primary structure (or primary sequence) of an unbranched biopolymer. ...


In 1998, Woese described a novel hypothesis that posits that during early life on earth, horizontal gene transfer within a common "colony" dominated the evolutionary process, eventually giving rise to the division into the three domains, where vertical gene transfer became dominant.[23] According to Woese, this combination of horizontal and vertical gene transfer could explain the differing pictures of the evolutionary history of Archaea, Bacteria and Eukaryotes that are given by analyses that examine different genes; since although the set of genes within the genomes of a species will be inherited as a group in modern organisms, these genes might not have been inherited together in the past. Instead genomes could have been assembled by the free exchange of genes between the members of an ancestral community of ancient organisms.


Classification

Phylogenetic tree showing extensive horizontal gene transfer between domains and an ancestral colony as the root of the tree.
Phylogenetic tree showing extensive horizontal gene transfer between domains and an ancestral colony as the root of the tree.
Further information: Scientific classification and Systematics

The classification of archaea, and of prokaryotes in general, is a rapidly-moving and contentious field. These classification systems aim to organize archaea into groups of organisms that share structural features and common ancestors.[24] This follows the classification of other organisms, with a popular definition of a species in animals being a set of actually or potentially interbreeding populations that are reproductively isolated from other such groups.[25] However, efforts to classify prokaryotes such as archaea into species are complicated by the fact that they are asexual and show high levels of horizontal gene transfer between lineages. The area is controversial, with for example, some arguing that in groups such as the genus Ferroplasma, related archaea form population clusters that can be seen as species.[26] On the other hand, studies in Halorubrum found significant genetic exchange between such population clusters.[27] Such results have led to the argument that prokaryotic species are points within an interconnected net of gene transfer events, rather than parts of a standard phylogenetic tree.[28] Fig. ... Horizontal gene transfer (HGT), also Lateral gene transfer (LGT), is any process in which an organism transfers genetic material to another cell that is not its offspring. ... For other uses, see Scientific classification (disambiguation). ... Biological systematics is the study of the diversity of life on the planet earth, both past and present, and the relationships among living things through time. ... For other uses, see Species (disambiguation). ... For other uses, see Animal (disambiguation). ... An important concept in evolutionary biology, reproductive isolation is a category of mechanisms that prevent two or more populations from exchanging genes. ... Horizontal gene transfer (HGT), also Lateral gene transfer (LGT), is any process in which an organism transfers genetic material to another cell that is not its offspring. ... Species Synonyms In taxonomy, Ferroplasma is a genus of the Ferroplasmaceae. ... Fig. ...


The current state of knowledge on archaean diversity is fragmentary.[29] Estimates of the total number of phylum-level lineages in the archaea range from 18 to 23, of which only 8 phyla have representatives that have been grown in culture and studied directly. Many of these hypothetical groups are known from only a single rRNA sequence, indicating that the vast majority of the diversity among these organisms remains completely unknown.[30] This problem of how to study and classify an uncultured microbial majority is common across all prokaryotes.[31]


Most of the well-studied species of archaea are members of two main phyla, the Euryarchaeota and Crenarchaeota. Other groups have been tentatively created, such as the peculiar species Nanoarchaeum equitans that was discovered in 2003 has been given its own phylum, the Nanoarchaeota;[32] and the phylum Korarchaeota that contains a small group of thermophilic species, which are most closely related to the Crenarchaeota.[33] Other recently-detected species of archaea cannot be easily classified within any of these groups, such as the Archael Richmond Mine Acidophilic Nanoorganisms (ARMAN) that were discovered in 2006.[34] In biological taxonomy, a phylum (Greek plural: phyla) is a taxon in the rank below kingdom and above class. ... Classes Archaeoglobi Halobacteria Methanobacteria Methanococci Methanomicrobia Methanopyri Thermococci Thermoplasmata The Euryarchaeota are a major group of Archaea. ... Orders Caldisphaerales Cenarchaeales Desulfurococcales Sulfolobales Thermoproteales The Crenarchaeota are a major group of Archaea, containing many extremely thermophilic and psychrophilic organisms. ... Binomial name Nanoarchaeum equitans Nanoarchaeum equitans is a species of tiny microbe, discovered in 2002 in a hydrothermal vent off the coast of Iceland by Karl Stetter. ... Nanoarchaeum equitans is a species of tiny microbe, discovered in 2002 in a hot vent off the coast of Iceland by Karl Stetter. ... The Korarchaeota are a group of Archaea known only from 16S rRNA gene sequences obtained from samples of high temperature hydrothermal environments. ... Archaeal Richmond Mine Acidophilic Nanoorganisms (ARMAN) were first discovered in an extremely acidic mine located in northern California (Iron Mountain Mine) by Baker et al in Jillian F. Banfields laboratory at the University of California Berkeley. ...


Morphology and physiology

The sizes of prokaryotic cells relative to other cells and biomolecules.
The sizes of prokaryotic cells relative to other cells and biomolecules.

Image File history File links Relative_scale. ... Image File history File links Relative_scale. ...

Size and shape

Individual archaeans range from 0.1 micrometres (μm) to over 15 μm in diameter, and occur in various shapes, commonly as spheres, rods, spirals or plates.[35] Other morphologies in the Crenarchaeota include irregularly-shaped lobed cells in Sulfolobus, thin needle-like filaments that are less than half a micometre in diameter in Thermofilum, and almost perfectly rectangular rods in Thermoproteus and Pyrobaculum.[36] Recently, even a species of flat, square archaea called Haloquadra walsbyi that lives in hypersaline pools has been discovered.[37] These unusual shapes are probably maintained both by their cell walls and a prokaryotic cytoskeleton, but in contrast to the bacteria, these cellular structures are poorly understood in archaea.[38] However, proteins related to the cytoskeleton components of other organisms have been identified in the archaea,[39] and filaments have been observed within these cells.[40] A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... Orders Caldisphaerales Cenarchaeales Desulfurococcales Sulfolobales Thermoproteales The Crenarchaeota are a major group of Archaea, containing many extremely thermophilic and psychrophilic organisms. ... Species Sulfolobus is a genus of the prokaryote domain of archaea. ... Elements of the Caulobacter crescentus cytoskeleton. ...


Some species of archaea form aggregates or filaments of cells up to 200 μm in length,[35] and these organisms can be prominent members of the communities of microbes that make up biofilms.[41] A particularly elaborate form of multicellular colonies are produced by archaea in the genus Pyrodictium. Here, the cells produce arrays of long, thin hollow tubes called cannulae, that stick out from the cells' surfaces and connect them together into a dense bush-like colony.[42] The function of these cannulae is not known, but they may allow the cells to communicate or exchange nutrients with their neighbors.[43] Staphylococcus aureus biofilm on an indwelling catheter. ...


Comparison of archaeal, bacterial and eukaryotic cells

Archaea are similar to other prokaryotes in many aspects of their cell structure and metabolism, but other characteristics set the Archaea apart. Prokaryotic bacteria cell structure Prokaryotes (IPA: //) are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ...


Like bacteria and eukaryotes, archaea possess glycerol-based phospholipids called ether lipids.[44] However, three features of archaeal lipids are highly unusual:[45] Glycerine, Glycerin redirects here. ... Two schematic representations of a phospholipid. ... An ether lipid is a lipid in which one or more of the carbon atoms on glycerol is bonded to an alkyl chain via an ether linkage, as opposed to the usual ester linkage. ...

Membrane structures. Top: archaeal membrane, 1-isoprene sidechain, 2-ether linkage, 3-L-glycerol, 4-phosphate moieties. Middle: bacterial and eukaryan membrane: 5-fatty acid, 6-ester linkage, 7-D-glycerol, 8-phosphate moieties. Bottom: 9-lipid bilayer of bacteria and eukarya, 10-lipid monolayer of some archaea.
Membrane structures. Top: archaeal membrane, 1-isoprene sidechain, 2-ether linkage, 3-L-glycerol, 4-phosphate moieties. Middle: bacterial and eukaryan membrane: 5-fatty acid, 6-ester linkage, 7-D-glycerol, 8-phosphate moieties. Bottom: 9-lipid bilayer of bacteria and eukarya, 10-lipid monolayer of some archaea.
  • The archaeal lipids are unique because the stereochemistry of the glycerol is the reverse of that found in bacterial and eukaryotic lipids - the glycerol components of these lipids are mirror images of each other. In archaea, acyl chains are attached to the sn-2 and sn-3 positions of the glycerol, while bacterial and eucaryal lipids have acyl chains at the sn-1 and sn-2 positions. This is strong evidence for a different biosynthetic pathway.
  • Most bacteria and eukaryotes have membranes composed mainly of glycerol-ester lipids, whereas archaea have membranes composed of glycerol-ether lipids. Even when bacteria have ether-linked lipids, the stereochemistry of the glycerol is the bacterial form. These differences may be an adaptation on the part of Archaea to hyperthermophily. However, it is worth noting that even mesophilic archaea have ether-linked lipids.
  • Archaeal lipids are based upon the isoprenoid sidechain. Only the archaea incorporate these compounds into their cellular lipids, frequently as C-20 (four monomers) or C-40 (eight monomers) side-chains. In some archaea, the C-40 isoprenoid side-chain is long enough to span the membrane, forming a monolayer for a cell membrane with glycerol phosphate moieties on both ends. Although dramatic, this adaptation is most common in the extremely thermophilic archaea.

The different types of isomers. ... For other uses, see Ester (disambiguation). ... Some common lipids. ... An ether lipid is a lipid in which one or more of the carbon atoms on glycerol is bonded to an alkyl chain via an ether linkage, as opposed to the usual ester linkage. ... Hyperthermophiles produce some of the bright colors of Grand Prismatic Spring, Yellowstone National Park A hyperthermophile is an organism that thrives in extremely hot environments - that is, hotter than around 60°C. The optimal temperatures are between 80°C and 110°C; in fact, the recently-discovered Strain 121 [1... Isoprene is a common synonym for the chemical compound 2-methyl-1,3-butadiene. ... Look up cell membrane in Wiktionary, the free dictionary. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Thermophiles produce some of the bright colors of Grand Prismatic Spring, Yellowstone National Park A thermophile is an organism – a type of extremophile – which thrives at relatively high temperatures, up to about 60 °C. Many thermophiles are archaea. ...

Cell wall and flagella

Further information: Cell wall

Although not unique, archaeal cell walls are also unusual. For instance, in most archaea they are formed by surface-layer proteins or an S-layer.[46] S-layers are also found in some bacteria, where they serve as the sole cell-wall component in some organisms (like the Planctomyces) or an outer layer in many organisms with peptidoglycan. With the exception of one group of methanogens, archaea lack a peptidoglycan wall (and in the case of the exception, the peptidoglycan is very different from the type found in bacteria).[47] Plant cells separated by transparent cell walls. ... Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria. ...


Archaeans also have flagella that are notably different in composition and development from the superficially similar flagella of bacteria.[48] The bacterial flagellum is a modified type III secretion system, while archeal flagella appear to be homologous to the bacterial type IV pili.[49] For the insect anatomical structure, see Antenna (biology). ... In biology, homology is any similarity between structures that is due to their shared ancestry. ... Image of bacteriological pili or fimbriae A pilus (Latin; plural : pili) is a hairlike structure on the surface of a cell, especially Gram-negative bacteria, a protein appendage required for bacterial conjugation. ...


Metabolism

Further information: Microbial metabolism

Archaea exhibit a variety of different types of metabolism; there are nitrifiers, methanogens and anaerobic methane oxidisers.[4] Methanogens live in anaerobic environments and produce methane. Of note are the halobacteria, which use light to produce energy. Although no archaea fix carbon through photosynthesis, in some archaea light-activated ion pumps like bacteriorhodopsin and halorhodopsin generate ion gradients, which are converted into adenosine triphosphate (ATP).[35] Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... This article or section does not cite its references or sources. ... It has been suggested that Anoxic sea water, Oxygen minimum zone, and Hypoxic zone be merged into this article or section. ... Genera Haloarcula Halobacterium Halobaculum Halococcus Haloferax Halogeometricum Halorubrum Haloterrigena Natrialba Natrinema Natronobacterium Natronococcus Natronomonas Natronorubrum The halobacteria are a family of archaea, found in water saturated or nearly saturated with salt. ... Carbon fixation is a process found in autotrophs, usually driven by photosynthesis, whereby carbon dioxide is changed into organic materials. ... assimilation. ... Bacteriorhodopsin is a photosynthetic pigment used by archaea, most notably halobacteria. ... Halorhodopsin is a light-driven ion pump, specific for chloride ions, and found in phylogenetically ancient bacteria (archaea), known as halobacteria. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...


Reproduction

Further information: Asexual reproduction

Archaea reproduce asexually by binary or multiple fission, fragmentation, or budding; meiosis does not occur, so if a species of archaea exists in more than one form, these will all have the same number of chromosomes (they have the same karyotype).[35] Cell division is controlled in the archaea as part of a complex cell cycle where the cell's chromosome is replicated, the two daughter chromosomes are separated, and the cell then divides.[50] The details of the archaeal cell cycle have only been investigated in the genus Sulfolobus, but here it has characters that are similar to both bacterial and eukaryotic systems: with the chromosomes being replicated from multiple starting-points (origins of replication) using DNA polymerases that are similar to the equivalent eukaryotic enzymes.[51] However, the proteins that direct cell division, such as the protein FtsZ, which forms a contracting ring around the cell, and the components of the septum that is constructed across the center of the cell, appear to be closer to their bacterial equivalents.[50] It has been suggested that Parthenogenesis be merged into this article or section. ... For the figure of speech, see meiosis (figure of speech). ... Karyogram of human male using Giemsa staining. ... This does not adequately cite its references or sources. ... The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication. ... A scheme of a condensed (metaphase) chromosome. ... Species Sulfolobus is a genus of the prokaryote domain of archaea. ... The origin of replication (also called the replication origin) is a particular DNA sequence at which DNA replication is initiated. ... 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ... FtsZ is a protein encoded by the ftsZ gene that assembles into a ring at the future site of the septum of bacterial cell division. ... Look up septum in Wiktionary, the free dictionary. ...


Spores, such as the endospores made by some bacteria, are not formed in any of the known archaea,[52] although some species of haloarchaea can undergo phenotypic switching and grow as several different types of cell, including thick-walled structures that are resistant to osmotic shock and allow them to survive in water at low concentrations of salt.[53] These are not reproductive structures, but may instead help these species disperse to new habitats. An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria from the Firmicute family. ... Haloarchaea are a member of the halophile community, in that they require high salt concentrations to grow. ... Phenotypic switching (a. ... Osmotic shock is a condition that inhibits cellular activity. ...


Genetics

Further information: Plasmid, Genome

Archaea are similar to bacteria in that they usually have a single circular chromosome.[54] These range in size from 5,751,492 base pairs in Methanosarcina acetivorans,[55] the largest archaean genome sequenced to date, to the tiny 490,885 base-pair genome of Nanoarchaeum equitans, which is the smallest microbial genome known and may contain only 537 protein-encoding genes.[56] Plasmids are also found in archaea, and can spread between cells by physical contact, in a process that may be similar to bacterial conjugation.[57] Figure 1: Illustration of a bacterium with plasmids enclosed showing chromosomal DNA and plasmids. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... A scheme of a condensed (metaphase) chromosome. ... Base pairs, of a DNA molecule. ... Binomial name Methanosarcina acetivorans Methanosarcina acetivorans is a versatile methane producing microbe which is found in such diverse environments as oil wells, trash dumps, deap sea hydrothermal vents, and oxygen depleted sediments beneath kelp beds. ... Binomial name Nanoarchaeum equitans Nanoarchaeum equitans is a species of tiny microbe, discovered in 2002 in a hydrothermal vent off the coast of Iceland by Karl Stetter. ... Figure 1: Illustration of a bacterium with plasmids enclosed showing chromosomal DNA and plasmids. ... Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact. ...

Sulfolobus infected with the DNA virus STSV1. Bar is 1 micrometre.
Sulfolobus infected with the DNA virus STSV1.[58] Bar is 1 micrometre.

As with the bacteriophages that infect bacteria, viruses exist that replicate within archaea: these are double-stranded DNA viruses that appear to be unrelated to any other form of virus and can have a variety of unusual shapes, with some resembling bottles, hooked rods, or teardrops.[59] These viruses have been studied in most detail in the thermophilic archaea, particularly the orders Sulfolobales and Thermoproteale.[60] Defenses against these viruses may involve RNA interference from repetitive DNA sequences within archaean genomes that are related to the genes of the viruses.[61][62] Image File history File linksMetadata RT8-4. ... Image File history File linksMetadata RT8-4. ... Species Sulfolobus is a genus of the prokaryote domain of archaea. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the diameter of a droplet of mist or fog. ... An artists rendering of an Enterobacteria phage T4. ... A DNA virus is a virus belonging to either Group I or Group II of the Baltimore classification system for viruses. ... Cells use dicer to trim double stranded RNA to form small interfering RNA or microRNA. An exogenous dsRNA or endogenous pre-miRNA can be processed by dicer and incorporated into the RNA-induced silencing complex (RISC), which targets single-stranded messenger RNA molecules and triggers translational repression;[1] incorporation into... In the study of DNA sequences, one can distinguish two main types of repeated sequence: Tandem repeats: Satellite DNA, Minisatellite, Microsatellite; Interspersed repeats: SINE (Short INterspersed Elements), LINE (Long INterspersed Elements). ...


Archaea are genetically distinct from other organisms, with up to 15% of the proteins encoded by any one archaeal genome being unique to the Archaea, although most of these unique genes have no known function.[63] Of the remainder of the genes that are unique to archaea and do have an identified function, most are involved in methanogenesis. The genes that are shared between archaea, bacteria and eukaryotes form a common core of cell function, relating mostly to transcription, translation, and nucleotide metabolism.[64] Other characteristic features of archaean genomes are the organization of genes of related function, such as enzymes catalysing steps in the same metabolic pathway, into novel operons, and large differences in tRNA genes and their aminoacyl tRNA synthetases.[64] A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Translation is the second stage of protein biosynthesis (part of the overall process of gene expression). ... A nucleotide is a chemical compound that consists of 3 portions: a heterocyclic base, a sugar, and one or more phosphate groups. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... An operon is a group of key nucleotide sequences including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... An aminoacyl tRNA synthetase (abbreviated aaRs) is an enzyme that catalyzes the binding of a specific amino acid to a tRNA to form an aminoacyl-tRNA. The synthetase hydrolyzes ATP to bind the appropriate amino acid to the 3 hydroxyl of the tRNA molecule. ...


Transcription and translation in archaea are more similar to that in eukaryotes than in bacteria, with both the RNA polymerase II and the ribosomes of archaea sharing both subunits and sequence similarity with their equivalents in eukaryotes.[54] The function and interactions of the archaeal RNA polymerase in transcription also seems to be related to that of eukaryotes, with similar assemblies of proteins (the general transcription factors) directing the binding of the RNA polymerase to a gene's promoter. However, many other archaean transcription factors are similar to those seen in bacteria.[65] RNA polymerase II (also called RNAP II and Pol II) transcribes DNA to synthesize precursors of mRNA and most snRNA. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... General transcription factors (GTFs) are proteins which have been shown to be important in the transcription of class II genes to mRNA templates. ... A promoter is a regulatory region of DNA located upstream (towards the 5 region) of a gene, providing a control point for regulated gene transcription. ... In molecular biology, a transcription factor is a protein that binds DNA at a specific promoter or enhancer region or site, where it regulates transcription. ...


Habitats and interactions with other organisms

Multiple archaeans are extremophiles, and some would say this is their ecological niche.[4] They can survive high temperatures, often above 100 °C, as found in geysers, black smokers, and oil wells. Some are found in very cold habitats and others in highly saline, acidic, or alkaline water. Mesophiles favor milder conditions in marshland, sewage and soil. Many methanogenic archaea are found in the digestive tracts of animals such as ruminants, termites, and humans. As of 2007, no clear examples of archaeal pathogens are known,[66][67] although a relationship has been proposed between the presence of some methanogens and human periodontal disease.[68] An extremophile is an organism, usually unicellular, which thrives in or requires extreme conditions that would exceed optimal conditions for growth and reproduction in the majority of mesophilic terrestrial organisms. ... Two lichens on a rock, in two different ecological niches In ecology, a niche; (pronounced nich, neesh or nish)[1] is a term describing the relational position of a species or population in its ecosystem[1]. The ecological niche; describes how an organism or population responds to the distribution of... For other uses, see Celsius (disambiguation). ... Strokkur geyser, Iceland A geyser is a type of hot spring that erupts periodically, ejecting a column of hot water and steam into the air. ... A black smoker in the Atlantic Ocean Black smokers are a type of hydrothermal vent found on the ocean floor. ... This article is about common table salt. ... For other uses, see Acid (disambiguation). ... The common (Arrhenius) definition of a base is a chemical compound that either donates hydroxide ions or absorbs hydrogen ions when dissolved in water. ... A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 25 and 40 °C (68 and 113 °F). ... This article is about marsh, a type of wetland. ... Sewage is the mainly liquid waste containing some solids produced by humans which typically consists of washing water, faeces, urine, laundry waste and other material which goes down drains and toilets from households and industry. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For the American hard rock band, see SOiL. For the System of a Down song, see Soil (song). ... Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. ... It has been suggested that this article or section be merged with Ruminantia. ... Families Mastotermitidae Kalotermitidae Termopsidae Hodotermitidae Rhinotermitidae Serritermitidae Termitidae Termites, sometimes known as white ants, are a group of social insects usually classified at the taxonomic rank of order Isoptera. ... A pathogen (from Greek pathos, suffering/emotion, and gene, to give birth to), infectious agent, or more commonly germ, is a biological agent that causes disease or illness to its host. ... Periodontitis a disease involving inflammation of the gums (gingiva), often persisting unnoticed for years or decades in a patient, that results in loss of bone around teeth. ...

Image of plankton in the oceans; archaea form a major part of oceanic life.
Image of plankton in the oceans; archaea form a major part of oceanic life.

Archaea are commonly placed into three physiological groups. These are the halophiles, thermophiles and acidophiles. These groups are not necessarily comprehensive or monophyletic, nor even mutually exclusive. Nonetheless, they are a useful starting point for ecological studies. Halophiles, including the genus Halobacterium, live in extremely saline environments and start outnumbering their bacterial counterparts at salinities greater than 20-25%.[4] These can be found in sediments or in the intestines of animals.[69] Thermophiles live in places that have high temperatures, such as hot springs. Where optimal growth occurs at greater than 80 °C, the archaeon is a hyperthermophyle, and the highest recorded temperature survived was 121 °C. Although thermophilic bacteria predominate at some high temperatures, archaea generally have the edge when acidity exceeds pH 5. True acidophiles withstand pH 0 and below.[4] For the SpongeBob SquarePants character, see Plankton (SpongeBob SquarePants). ... Animated map exhibiting the worlds oceanic waters. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... Halophiles are extremophiles that thrive in environments with very high concentrations of salt (at least 2 M, approximately ten times the salt level of ocean water). ... This article is about a type of organism. ... Acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 2. ... In phylogenetics, a group is monophyletic (Greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. ... Species H. salinarum Synonyms Halobacter Anderson 1954 Halobacter Halobacterium Elazari-Volcani 1957 not Halobacterium Schoop 1935 (nomen nudum) Note: The word halobacterium is also the singular form of the word halobacteria. In taxonomy, Halobacterium is a genus of the Halobacteriaceae. ... For other uses, see Acid (disambiguation). ...


Recently, several studies have shown that archaea exist not only in mesophilic and thermophilic environments but are also present, sometimes in high numbers, at low temperatures as well. It is increasingly becoming recognised that methanogens are commonly present in low-temperature environments such as cold sediments. Some studies have even suggested that at these temperatures the pathway by which methanogenesis occurs may change due to the thermodynamic constraints imposed by low temperatures. Perhaps even more significant are the large numbers of archaea found throughout most of the world's oceans, a predominantly cold environment. These archaea, which belong to several deeply branching lineages unrelated to those previously known, can be present in extremely high numbers (up to 40% of the microbial biomass) although almost none have been isolated in pure culture.[70] Currently we have almost no information regarding the physiology of these organisms, meaning that their effects on global biogeochemical cycles remain unknown. One recent study has shown, however, that one group of marine crenarchaeota are capable of nitrification, a trait previously unknown among the archaea.[71] Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. ... This article or section cites very few or no references or sources. ... Methanogenesis is the formation of methane by microbes. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... In biology, a pure culture is a population of identical cells originating from a single cell. ... The field of biogeochemistry involves scientific study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the hydrosphere, the pedosphere, the atmosphere, and the lithosphere), and the cycles of matter and energy that transport the Earths chemical... Orders Caldisphaerales Cenarchaeales Desulfurococcales Sulfolobales Thermoproteales The Crenarchaeota are a major group of Archaea, containing many extremely thermophilic and psychrophilic organisms. ... Nitrogen cycle Nitrification is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates. ...


Significance in technology and industry

Further information: Biotechnology

Extremophile archaea, particularly organisms that are resistant to heat, or extremes of acidity and alkalinity, are a source of enzymes that can function under these harsh conditions.[72][73] These enzymes have a wide range of uses. For example, thermostable DNA polymerases, such as the Pfu DNA polymerase from Pyrococcus furiosus, have revolutionized molecular biology by allowing the polymerase chain reaction to be used as a simple and rapid technique for cloning DNA. In industry, amylases, galactosidases and pullulanases in other species of Pyrococcus that function at over 100 °C allow food processing at high temperatures, such as the production of low lactose milk and whey.[74] Enzymes from these thermophilic archaea also tend to be very stable in organic solvents, so can be used in a broad range of environmentally-friendly processes in green chemistry that synthesize organic compounds.[73] The structure of insulin Biotechnology is technology based on biology, especially when used in agriculture, food science, and medicine. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... 3D structure of the DNA-binding helix-hairpin-helix motifs in human DNA polymerase beta A DNA polymerase is an enzyme that assists in DNA replication. ... Pfu DNA polymerase is an enzyme found in the hyperthermophilic archaeon Pyrococcus furiosus, where it functions in vivo to replicate the organisms DNA. In vitro, Pfu is used to quickly amplify DNA in the Polymerase Chain Reaction, where the enzyme serves the central function of copying a new strand... Binomial name Pyrococcus furiosus Erauso et al. ... Molecular biology is the study of biology at a molecular level. ... “PCR” redirects here. ... For the cloning of human beings, see human cloning. ... Amylase is the name given to glycoside hydrolase enzymes that break down starch into glucose molecules. ... Galactosidases are enzymes (glycoside hydrolases) which catalyzes the hydrolysis of galactosides into monosaccharides If the galactoside is an alpha-galactoside, the enzyme is called alpha-galactosidase, and if it is a beta-galactoside, it is called beta-galactosidase. ... Pullulanase is a specific kind of glucanase, an amylolytic exoenzyme, that degrades pullulan. ... Species P. furiosus Synonyms Pyrococcus Fiala and Stetter 1986 In taxonomy, Pyrococcus is a genus of the Thermococcaceae. ... Food processing is the set of methods and techniques used to transform raw ingredients into food for consumption by humans or animals. ... Green chemistry is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances. ...


In contrast to the range of applications of archaean enzymes, the use of the organisms themselves in biotechnology are more restricted. However, methanogenic archaea are a vital part of sewage treatment, since they are part of the community of microorganisms that carry out anaerobic digestion and produce biogas.[75] Acidophillic archaea also show promise in the extraction of metals such as gold, cobalt and copper from ores in mineral processing.[76] Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater, both runoff and domestic. ... Anaerobic digestion component of Lübeck mechanical biological treatment plant in Germany, 2007 Anaerobic digestion is a process in which microorganisms break down biodegradable material in the absence of oxygen. ... Biogas-bus in Bern, Switzerland Biogas typically refers to a (biofuel) gas produced by the anaerobic digestion or fermentation of organic matter including manure, sewage sludge, municipal solid waste, biodegradable waste or any other biodegradable feedstock, under anaerobic conditions. ... Mineral processing, otherwise known as mineral dressing, is the practice of beneficiating valuable minerals from their ores. ...


A new class of potentially useful antibiotics are derived from the Archaea group of organisms. Eight of these archaeocins have been characterized, but hundreds more are believed to exist, especially within the haloarchaea. The discovery of new archaeocins hinges on recovery and cultivation of archaeal organisms from the environment. [77]


See also

This list of sequenced archaeal genomes contains all the archaeal known to have publically available complete genome sequences that have been assembled, annotated and published; draft genomes are not included. ...

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A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

Further reading

  • Howland, John L. (2000). The Surprising Archaea: Discovering Another Domain of Life. Oxford: Oxford University Press. ISBN 0-19-511183-4. 
  • Martinko JM, Madigan MT (2005). Brock Biology of Microorganisms, 11th ed., Englewood Cliffs, N.J: Prentice Hall. ISBN 0-13-144329-1. 
  • Garrett RA, Klenk H (2005). Archaea: Evolution, Physiology and Molecular Biology. WileyBlackwell. ISBN 1-40-514404-1. 
  • Cavicchioli R (2007). Archaea: Molecular and Cellular Biology. American Society for Microbiology. ISBN 1-55-581391-7. 
  • Blum P (editor). (2008). Archaea: New Models for Prokaryotic Biology. Caister Academic Press. ISBN 978-1-904455-27-1 . 

External links

Wikispecies has information related to:
Archaea

General Image File history File links Wikispecies-logo. ... Wikispecies is a wiki-based online project supported by the Wikimedia Foundation that aims to create a comprehensive free content catalogue of all species (including animalia, plantae, fungi, bacteria, archaea, and protista). ...

  • ArchaeaWeb - by UNSW - Information about Archaea
  • Introduction to the Archaea, ecology, systematics and morphology

Classification

  • NCBI taxonomy parge on Archaea
  • Tree of Life illustration showing how Archaea relates to other lifeforms

Genomics

  • Browse any completed archaeal genome at UCSC
  • Comparative Analysis of Archaeal Genomes (at DOE's IMG system)
Species H. salinarum Synonyms Halobacter Anderson 1954 Halobacter Halobacterium Elazari-Volcani 1957 not Halobacterium Schoop 1935 (nomen nudum) Note: The word halobacterium is also the singular form of the word halobacteria. In taxonomy, Halobacterium is a genus of the Halobacteriaceae. ... A hydrothermal vent A hydrothermal vent is a fissure in a planets surface from which geothermally heated water issues. ... Binomial name Methanopyrus kandleri AV19 Slesarev AI et al. ... Radioresistance is the property of organisms which are capable of living in environments with very high levels of ionizing radiation, such as around nuclear power plants, or near natural uranium mineral sites. ... Thermostability is the quality of a substance to resist irreversible change in its chemical or physical structure at high temperature. ... Species Thermotoga elfii Thermotoga hypogea Thermotoga lettingae Thermotoga maritima Thermotoga naphthophila Thermotoga neapolitana Thermotoga petrophila Thermotoga subterranea Thermotoga thermarum Thermotoga are thermophile or hyperthermophile bacteria whose cell is wrapped in an outer toga membrane. ...

  Results from FactBites:
 
Types of Microbes: Archaea (634 words)
There are three main types of archaea: the crenarchaeota (kren-are-key-oh-ta), which are characterized by their ability to tolerate extremes in temperature and acidity.
Although many archaea have tough outer cell walls, these walls contain different kinds of amino acids and sugars than those found in bacteria.
The archaea very much resemble bacteria, so much so that they were once thought to be a weird group of bacteria.
Archaea (600 words)
The archaea have a curious mix of traits characteristic of
have suggested that the archaea may be the little-changed descendants of the first forms of life on earth.
Archaea may also be enlisted to aid in cleaning up contaminated sites, e.g., petroleum spills.
  More results at FactBites »

 
 

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