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Archaea
Fossil range: Paleoarchean - Recent
Halobacteria sp. strain NRC-1, each cell about 5 μm in length.
Halobacteria sp. The Paleoarchean (ˌpeɪlɪoʊɑrˈkiːən also spelled Palaeoarchaean) is a geologic era within the Archaean. Note The word "halobacteria" is also the plural form of the word " Halobacterium " 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 Archaea (pronounced /ɑrˈkiːə/) are a group of prokaryotic, single-celled microorganisms. Neomura is a speculative Clade composed of the two domains of life of Archaea and Eukarya. Carl Richard Woese (born July 15 1928, Syracuse New York) is an American Microbiologist who attended Deerfield Academy In taxonomy, the Crenarchaeota (Greek for "spring old quality" (also known as Crenarchaea or eocytes) are a phylum of the In taxonomy, the Euryarchaeota (Greek for "broad old quality" are a phylum of the Archaea. In taxonomy, the Korarchaeota are a phylum of the Archaea. The Korarchaeota are a group of Archaea known only from 16S In taxonomy, the Nanoarchaeota (Greek "old dwarf" are a phylum of the Archaea. Archaeal Richmond Mine Acidophilic Nanoorganisms (ARMAN were first discovered in an extremely acidic mine located in northern California ( Iron Mountain Mine) by Brett Baker The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually In this they are similar to bacteria but these two groups evolved differently, and are classified as different domains in the three-domain system. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have In biological Taxonomy, a domain (also superregnum, superkingdom, or empire) is the highest Taxonomic rank of Organisms The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, Originally these organisms were named archaebacteria. However, this term has not been favored since the three-domain system became popular.

Although there is still uncertainty in the phylogeny, Archaea, Eukaryota and Bacteria were introduced as the fundamental classifications in what would later become the three-domain system by Carl Woese in 1977. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Carl Richard Woese (born July 15 1928, Syracuse New York) is an American Microbiologist who attended Deerfield Academy As prokaryotes, archaea are also classified in kingdom Monera in the traditional five-kingdom Linnaean taxonomy. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system Monera are bacteria and other mostly tiny single-celled organisms whose genetic material is loose in the cell Linnaean taxonomy is a method of classifying living things originally devised by (and named for Carolus Linnaeus, although it has changed considerably since his time 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. In Biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. 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. Neomura is a speculative Clade composed of the two domains of life of Archaea and Eukarya. Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. 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]

Archaea were originally described in extreme environments, but have since been found in all habitats and may contribute up to 20% of total biomass. An extremophile is an Organism that thrives in and may even require Physically or Geochemically extreme conditions that are detrimental to the A habitat (which is Latin for "it inhabits" is an Ecological or environmental area that is inhabited by a particular Species. Biomass, in Ecology, is the mass of living biological organisms in a given area or Ecosystem at a given time [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. Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of [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. In Grammar, an adjective is a word whose main syntactic role is to modify a Noun or Pronoun, giving more information about the The etymology is Ancient Greek, from ἀρχαία meaning "ancient things". Etymology is the study of the History of Words &mdash when they entered a language from what source and how their form and meaning have changed over time The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c

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. Microbiology (from Greek grc μῑκρος mīkros, "small" grc βίος bios, " Life " and grc -λογία Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as The term morphology in Biology refers to the outward appearance ( Shape, Structure, Colour, Pattern) of an Organism Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. For example, microbiologists tried to classify microorganisms based on the substances they consume, their shapes, and the structures of their cell walls. A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural [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. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance

Archaea were first detected in extreme environments, such as volcanic hot springs.
Archaea were first detected in extreme environments, such as volcanic hot springs. A hot spring is a spring that is produced by the emergence of geothermally heated Groundwater from the earth's crust.

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. Carl Richard Woese (born July 15 1928, Syracuse New York) is an American Microbiologist who attended Deerfield Academy Professor George Edward Fox (born December 17, 1945) is a researcher at The University of Houston. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other Ribosomal RNA ( rRNA) is the central component of the Ribosome, the protein manufacturing machinery of all living cells. [7] These two groups were originally named the Archaebacteria and Eubacteria and treated as kingdoms or subkingdoms, which Woese and Fox termed Urkingdoms. In biological Taxonomy, a kingdom or regnum is a Taxonomic rank in either (historically the highest rank or (in the new three-domain system 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. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, [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. 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. A hot spring is a spring that is produced by the emergence of geothermally heated Groundwater from the earth's crust. The salt lake or saline lake is a landlocked body of Water which has a concentration of Salts (mostly Sodium chloride) and other minerals significantly [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. Molecular biology is the study of Biology at a molecular level A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information [10][11]

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 timeline of the evolution of life outlines the major events in the development Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit This refers to the primordial period of earth history when prokaryotes were the only cellular organisms living on the planet. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called [12][13] Probable fossils of these ancient cells have been dated to almost 3. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. 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]

Phylogenetic tree showing the relationship between the archaea and other forms of life. Eukaryotes are colored red, archaea green and bacteria blue.
Phylogenetic tree showing the relationship between the archaea and other forms of life. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other [16] Eukaryotes are colored red, archaea green and bacteria blue. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have

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. The three-domain system is a Biological classification introduced by Carl Woese in 1990 that divides cellular life forms into Archaea, 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 the 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]

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. In taxonomy, the Euryarchaeota (Greek for "broad old quality" are a phylum of the Archaea. In taxonomy, the Crenarchaeota (Greek for "spring old quality" (also known as Crenarchaea or eocytes) are a phylum of the 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. Thermotoga are Thermophile or Hyperthermophile Bacteria whose cell is wrapped in an outer "toga" membrane [20]

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. The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. [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. For the sense of "sequencing" used in Electronic music, see the Music sequencer article 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 The term DNA sequencing encompasses biochemical methods for determining the order of the Nucleotide bases Adenine, Guanine, Cytosine [22]

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. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other
Further information: Biological classification and Systematics

The classification of archaea, and of prokaryotes in general, is a rapidly-moving and contentious field. 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 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. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. An important concept in evolutionary biology reproductive isolation is a category of mechanisms that prevent two or more Populations from exchanging genes [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. In taxonomy, Ferroplasma is a Genus of the Ferroplasmaceae. The genus Ferroplasma consists solely of F [26] On the other hand, studies in Halorubrum found significant genetic exchange between such population clusters. In taxonomy, Halorubrum is a genus of the Halobacteriaceae. [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. A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other [28]

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. A phylum ( Plural: phyla) is a Taxonomic rank between Kingdom and above Class. In taxonomy, the Euryarchaeota (Greek for "broad old quality" are a phylum of the Archaea. In taxonomy, the Crenarchaeota (Greek for "spring old quality" (also known as Crenarchaea or eocytes) are a phylum of the 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. Nanoarchaeum equitans is a species of tiny Microbe, discovered in 2002 in a Hydrothermal vent off the coast of Iceland by Karl In taxonomy, the Nanoarchaeota (Greek "old dwarf" are a phylum of the Archaea. In taxonomy, the Korarchaeota are a phylum of the Archaea. The Korarchaeota are a group of Archaea known only from 16S [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. Archaeal Richmond Mine Acidophilic Nanoorganisms (ARMAN were first discovered in an extremely acidic mine located in northern California ( Iron Mountain Mine) by Brett Baker [34]

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.

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. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre [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. In taxonomy, the Crenarchaeota (Greek for "spring old quality" (also known as Crenarchaea or eocytes) are a phylum of the In taxonomy, Sulfolobus is a Genus of the Sulfolobaceae. Sulfolobus species grow in volcanic springs with optimal In taxonomy, Thermofilum is a genus of the Thermofilaceae. In taxonomy, Thermoproteus is a genus of the Thermoproteaceae. In taxonomy, Pyrobaculum is a genus of the Thermoproteaceae. [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. The prokaryotic cytoskeleton is the collective name for all structural filaments in Prokaryotes. [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]

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. A biofilm is a structured community of Microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface [41] A particularly elaborate form of multicellular colonies are produced by archaea in the genus Pyrodictium. In taxonomy, Pyrodictium is a genus of the Pyrodictiaceae. 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]

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. The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life.

Like bacteria and eukaryotes, archaea possess glycerol-based phospholipids called ether lipids. Phospholipids are a class of Lipids and are a major component of all Biological membranes All phospholipids contain a Diglyceride, a Phosphate Ether lipids are Lipids in which one or more of the Carbon Atoms on Glycerol is bonded to an Alkyl chain via an Ether linkage [44] However, three features of archaeal lipids are highly unusual:[45]

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.

Cell wall and flagella

Further information: Cell wall

Although not unique, archaeal cell walls are also unusual. A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural 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. Not to be confused with Glycoprotein. Peptidoglycan, also known as murein, is a Polymer consisting of sugars and amino 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]

Archaeans also have flagella that are notably different in composition and development from the superficially similar flagella of bacteria. A flagellum ( plural flagella) is a tail-like structure that projects from the Cell body of certain Prokaryotic and Eukaryotic cells and it [48] The bacterial flagellum is a modified type III secretion system, while archeal flagella appear to be homologous to the bacterial type IV pili. Secretion is the process of segregating elaborating and releasing chemicals from a cell, or a secreted Chemical substance or amount of substance In Evolutionary biology, homology has come to mean any similarity between characters that is due to their shared ancestry. A pilus ( Latin for 'hair' plural: pili) is a hairlike appendage found on the surface of many bacteria. [49]

Metabolism

Further information: Microbial metabolism

Archaea exhibit a variety of different types of metabolism; there are nitrifiers, methanogens and anaerobic methane oxidisers. Microbial metabolism is the means by which a Microbe obtains the energy and nutrients (e Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. Nitrifying bacteria are chemoautotrophic bacteria that grow at the expense of inorganic nitrogen compounds [4] Methanogens live in anaerobic environments and produce methane. For other uses of the term "hypoxia" see Hypoxia. Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments Of note are the halobacteria, which use light to produce energy. Note The word "halobacteria" is also the plural form of the word " Halobacterium " 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). Carbon fixation is a process found in Autotrophs (organisms that produce their own food usually driven by Photosynthesis, whereby Carbon dioxide is changed Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Bacteriorhodopsin is a protein 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 [35]

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). Asexual reproduction is a form of reproduction which does not involve Meiosis, Ploidy reduction or Fertilization. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half A karyotype is the characteristic Chromosome complement of a Eukaryote Species. [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. Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication A chromosome is an organized structure of DNA and Protein that is found in cells. [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. In taxonomy, Sulfolobus is a Genus of the Sulfolobaceae. Sulfolobus species grow in volcanic springs with optimal The Origin of replication (also called the replication origin) is a particular sequence in a Genome at which replication is initiated A DNA Polymerase is an Enzyme that assists in DNA replication. [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. FtsZ is a Protein encoded by the ftsZ Gene that assembles into a ring at the future site of the A septum ( Latin: something that encloses; plural Septa) is a partition separating two cavities or spaces [50]

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. An endospore is a dormant, tough and non-reproductive structure produced by a small number of Bacteria from the Firmicute phylum Haloarchaea are Microrganisms member of the Halophile community in that they require high salt concentrations to grow Phenotypic switching (aka phenotypic dimorphism is switching between two cell-types Osmotic shock or osmotic stress is a sudden change in the solute concentration around a cell, causing a rapid change in the movement of water across its [53] These are not reproductive structures, but may instead help these species disperse to new habitats.

Genetics

Further information: Plasmid, Genome

Archaea are similar to bacteria in that they usually have a single circular chromosome. A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA In classical genetics the genome of a Diploid Organism including Eukarya refers to a full set of chromosomes or genes in a Gamete, thereby A chromosome is an organized structure of DNA and Protein that is found in cells. [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. In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called Methanosarcina acetivorans is a versatile methane producing microbe which is found in such diverse environments as oil wells trash dumps deep sea hydrothermal Nanoarchaeum equitans is a species of tiny Microbe, discovered in 2002 in a Hydrothermal vent off the coast of Iceland by Karl [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. A plasmid is an extra-chromosomal DNA molecule separate from the chromosomal DNA which is capable of replicating independently of the chromosomal DNA Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact [57][58] Archaeal plasmids are increasingly important as genetic tools and allow the performance of genetic studies in archaea. [59]

Sulfolobus infected with the DNA virus STSV1. Bar is 1 micrometre.
Sulfolobus infected with the DNA virus STSV1. In taxonomy, Sulfolobus is a Genus of the Sulfolobaceae. Sulfolobus species grow in volcanic springs with optimal [60] Bar is 1 micrometre. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre

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. This article is about a biological infectious particle for other uses see Phage (disambiguation. A DNA virus is a Virus that has DNA as its Genetic material and replicates using a DNA-dependent DNA polymerase. [61] These viruses have been studied in most detail in the thermophilic archaea, particularly the orders Sulfolobales and Thermoproteale. [62] Defenses against these viruses may involve RNA interference from repetitive DNA sequences within archaean genomes that are related to the genes of the viruses. RNA interference ( RNAi) is a mechanism that inhibits Gene expression at the stage of translation or by hindering the transcription of specific In the study of DNA sequences one can distinguish two main types of repeated sequence: Tandem repeats Satellite DNA, [63][64]

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. [65] 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. Transcription is the synthesis of RNA under the direction of DNA Translation is the first stage of Protein biosynthesis (part of the overall process of Gene expression) Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group [66] 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. In Biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. An operon is a functioning unit of key Nucleotide sequences including an operator, a common Promoter, and one or more structural Genes, Transfer RNA (abbreviated tRNA) is a small RNA (usually about 74-95 nucleotides that transfers a specific Amino acid to a growing polypeptide chain at An aminoacyl tRNA synthetase ( aaRS) is an Enzyme that catalyzes the Esterification of a specific Amino acid or its precursor to one of all its compatible [66]

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. RNA polymerase II (also called RNAP II and Pol II) is an enzyme found in eukaryotic cells Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that [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. General transcription factors (GTF's or basal transcription factors are Protein Transcription factors that have been shown to be important in the In Biology, a promoter is a region of DNA that facilitates the transcription of a particular Gene. However, many other archaean transcription factors are similar to those seen in bacteria. In the field of Molecular biology, a transcription factor (sometimes called a sequence-specific DNA binding factor is a Protein that binds to specific sequences [67]

Habitats and interactions with other organisms

Multiple archaeans are extremophiles, and some would say this is their ecological niche. An extremophile is an Organism that thrives in and may even require Physically or Geochemically extreme conditions that are detrimental to the In Ecology, a niche (pronounced nich nēsh or nish A shorthand definition of niche is how an organism makes a living [4] They can survive high temperatures, often above 100 °C, as found in geysers, black smokers, and oil wells. The Celsius Temperature scale was previously known as the centigrade scale. A geyser is a Hot spring characterized by intermittent discharge of water ejected turbulently and accomplished by a vapour phase A black smoker or sea vent is a type of Hydrothermal vent found on the Ocean floor. Some are found in very cold habitats and others in highly saline, acidic, or alkaline water. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, an alkali (from Arabic: Al-Qaly القلي القالي) is a basic, ionic salt of an Alkali metal Mesophiles favor milder conditions in marshland, sewage and soil. A mesophile is an Organism that grows best in moderate Temperature, neither too hot nor too cold typically between 15 and 40 °C (77 and 104 °F In Geography, a marsh, or morass, is a type of Wetland which is subject Sewage is the mainly liquid Waste containing some solids produced by humans which typically consists of washing water Feces, Urine, laundry waste and other Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel Many methanogenic archaea are found in the digestive tracts of animals such as ruminants, termites, and humans. Methanogens are Archaea that produce Methane as a Metabolic byproduct in Anoxic conditions Physiologically a ruminant is a Mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first stomach known The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy As of 2007, no clear examples of archaeal pathogens are known,[68][69] although a relationship has been proposed between the presence of some methanogens and human periodontal disease. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious [70]

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. Plankton consist of any drifting Organisms ( Animals Plants Archaea, or Bacteria) that inhabit the Pelagic zone of An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere.

Archaea are commonly placed into three physiological groups. Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical These are the halophiles, thermophiles and acidophiles. Halophiles are Extremophiles that thrive in environments with very high concentrations of Salt. A thermophile is an organism &mdash a type of Extremophile &mdash which thrives at relatively high temperatures between 45 and 80 °C (113 and 176 °F Acidophilic organisms are those that thrive under highly acidic conditions (usually at PH 2 These groups are not necessarily comprehensive or monophyletic, nor even mutually exclusive. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor 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%. Note The word "halobacterium" is also the singular form of the word "halobacteria" [4] These can be found in sediments or in the intestines of animals. [71] 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. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are True acidophiles withstand pH 0 and below. [4]

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. Methanogens are Archaea that produce Methane as a Metabolic byproduct in Anoxic conditions Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of 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. Methanogenesis or biomethanation is the formation of Methane by Microbes known as Methanogens Organisms capable of producing methane have been In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " 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. A microbiological culture, AKA microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory [72] Currently we have almost no information regarding the physiology of these organisms, meaning that their effects on global biogeochemical cycles remain unknown. The field of biogeochemistry involves scientific study of the chemical, physical, geological, and biological processes and reactions One recent study has shown, however, that one group of marine crenarchaeota are capable of nitrification, a trait previously unknown among the archaea. In taxonomy, the Crenarchaeota (Greek for "spring old quality" (also known as Crenarchaea or eocytes) are a phylum of the Nitrification is the biological oxidation of Ammonia with oxygen into Nitrite followed by the oxidation of these nitrites into Nitrates Degradation [73]

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. Biotechnology is Technology based on Biology, especially when used in Agriculture, Food science, and Medicine. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins [74][75] 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. 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 Pyrococcus furiosus is an extremophilic species of Archaea. It is notable for having an optimum growth temperature of 100°C (a temperature which would Molecular biology is the study of Biology at a molecular level Cloning in Biology is the process of producing populations of genetically-identical individuals that occurs in nature when organisms such as Bacteria, Insects 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. Amylase is an Enzyme that breaks Starch down into Sugar. Amylase is present in human Saliva, where it begins the chemical process Galactosidases are Enzymes ( Glycoside hydrolases) which catalyzes the Hydrolysis of Galactosides into Monosaccharides Pullulanase is a specific kind of Glucanase, an amylolytic Exoenzyme, that degrades Pullulan. 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 or to transform food into other forms for consumption by [76] 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. Green chemistry, also called sustainable chemistry is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous [75]

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. Sewage treatment, or domestic wastewater treatment, is the process of removing Contaminants from Wastewater, both Runoff ( Effluents Anaerobic digestion is a series of processes in which Microorganisms break down Biodegradable material in the absence of Oxygen. See also Natural gas, Biofuel Biogas typically refers to a Gas produced by the biological breakdown of Organic matter in the [77] Acidophillic archaea also show promise in the extraction of metals such as gold, cobalt and copper from ores in mineral processing. Mineral processing, otherwise known as mineral dressing is the practice of beneficiating valuable minerals from their Ores Industrial mineral treatment processes usually combine [78]

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. Archaeocin is the name given to a new type of potentially useful Antibiotic that is derived from the Archaea group of organisms The discovery of new archaeocins hinges on recovery and cultivation of archaeal organisms from the environment. [79]

See also

References

  1. ^ a b Wang M, Yafremava LS, Caetano-Anollés D, Mittenthal JE, Caetano-Anollés G (2007). This article lists the genera of the Archaea. The following genus of the Archaea has not been assigned to a phylum: Genus This list of sequenced archaeal genomes contains all the archaeal known to have publicly available complete Genome sequences that have been assembled annotated and "Reductive evolution of architectural repertoires in proteomes and the birth of the tripartite world". Genome Res. 17 (11): 1572–85. doi:10.1101/gr.6454307. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17908824.  
  2. ^ DeLong EF, Pace NR (2001). "Environmental diversity of bacteria and archaea". Syst. Biol. 50 (4): 470–8. doi:10.1080/106351501750435040. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 12116647.  
  3. ^ Karner MB, DeLong EF, Karl DM (2001). "Archaeal dominance in the mesopelagic zone of the Pacific Ocean". Nature 409 (6819): 507–10. doi:10.1038/35054051. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11206545.  
  4. ^ a b c d e Valentine DL (2007). "Adaptations to energy stress dictate the ecology and evolution of the Archaea". Nat. Rev. Microbiol. 5 (4): 316–23. doi:10.1038/nrmicro1619. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17334387.  
  5. ^ Staley JT (2006). "The bacterial species dilemma and the genomic-phylogenetic species concept". Philos. Trans. R. Soc. Lond. , B, Biol. Sci. 361 (1475): 1899–909. doi:10.1098/rstb.2006.1914. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17062409.  
  6. ^ Zuckerkandl E, Pauling L (1965). "Molecules as documents of evolutionary history". J. Theor. Biol. 8 (2): 357–66. doi:10.1016/0022-5193(65)90083-4. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 5876245.  
  7. ^ Woese C, Fox G (1977). "Phylogenetic structure of the prokaryotic domain: the primary kingdoms". Proc Natl Acad Sci USA 74 (11): 5088–90. doi:10.1073/pnas.74.11.5088. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 270744.  
  8. ^ Woese CR, Kandler O, Wheelis ML (1990). "Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya". Proc. Natl. Acad. Sci. U. S. A. 87 (12): 4576–9. doi:10.1073/pnas.87.12.4576. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 2112744.  
  9. ^ DeLong EF (1998). "Everything in moderation: archaea as 'non-extremophiles'". Curr. Opin. Genet. Dev. 8 (6): 649–54. doi:10.1016/S0959-437X(98)80032-4. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 9914204.  
  10. ^ Theron J, Cloete TE (2000). "Molecular techniques for determining microbial diversity and community structure in natural environments". Crit. Rev. Microbiol. 26 (1): 37–57. doi:10.1080/10408410091154174. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10782339.  
  11. ^ Schmidt TM (2006). "The maturing of microbial ecology". Int. Microbiol. 9 (3): 217–23. PMID 17061212.  
  12. ^ Altermann W, Kazmierczak J (2003). "Archean microfossils: a reappraisal of early life on Earth". Res Microbiol 154 (9): 611–7. doi:10.1016/j.resmic.2003.08.006. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 14596897.  
  13. ^ Cavalier-Smith T (2006). "Cell evolution and Earth history: stasis and revolution". Philos Trans R Soc Lond B Biol Sci 361 (1470): 969–1006. doi:10.1098/rstb.2006.1842. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16754610.  
  14. ^ Schopf J (2006). "Fossil evidence of Archaean life". Philos Trans R Soc Lond B Biol Sci 361 (1470): 869–85. doi:10.1098/rstb.2006.1834. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16754604.  
  15. ^ Brocks JJ, Logan GA, Buick R, Summons RE (1999). "Archean molecular fossils and the early rise of eukaryotes". Science 285 (5430): 1033–6. doi:10.1126/science.285.5430.1033. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10446042.  
  16. ^ Ciccarelli FD, Doerks T, von Mering C, Creevey CJ, Snel B, Bork P (2006). "Toward automatic reconstruction of a highly resolved tree of life". Science 311 (5765): 1283–7. doi:10.1126/science.1123061. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16513982.  
  17. ^ Woese CR, Gupta R (1981). "Are archaebacteria merely derived 'prokaryotes'?". Nature 289 (5793): 95–6. doi:10.1038/289095a0. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 6161309.  
  18. ^ Gupta RS (2000). "The natural evolutionary relationships among prokaryotes". Crit. Rev. Microbiol. 26 (2): 111–31. doi:10.1080/10408410091154219. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10890353.  
  19. ^ Gribaldo S, Brochier-Armanet C (2006). "The origin and evolution of Archaea: a state of the art". Philos. Trans. R. Soc. Lond. , B, Biol. Sci. 361 (1470): 1007–22. doi:10.1098/rstb.2006.1841. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16754611.  
  20. ^ Nelson KE, Clayton RA, Gill SR, et al (1999). "Evidence for lateral gene transfer between Archaea and bacteria from genome sequence of Thermotoga maritima". Nature 399 (6734): 323–9. doi:10.1038/20601. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10360571.  
  21. ^ Lake JA. (1988). "Origin of the eukaryotic nucleus determined by rate-invariant analysis of rRNA sequences". Nature 331 (6152): 184–6. doi:10.1038/331184a0. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 3340165.  
  22. ^ Complete Microbial Genomes NCBI Entrez Genome Project database
  23. ^ Woese C (1998). "The universal ancestor". Proc. Natl. Acad. Sci. U. S. A. 95 (12): 6854–9. doi:10.1073/pnas.95.12.6854. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 9618502.  
  24. ^ Gevers D, Dawyndt P, Vandamme P, et al (2006). "Stepping stones towards a new prokaryotic taxonomy". Philos. Trans. R. Soc. Lond. , B, Biol. Sci. 361 (1475): 1911–6. doi:10.1098/rstb.2006.1915. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17062410.  
  25. ^ de Queiroz K (2005). "Ernst Mayr and the modern concept of species". Proc. Natl. Acad. Sci. U. S. A. 102 Suppl 1: 6600–7. doi:10.1073/pnas.0502030102. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15851674.  
  26. ^ Eppley JM, Tyson GW, Getz WM, Banfield JF (2007). "Genetic exchange across a species boundary in the archaeal genus ferroplasma". Genetics 177 (1): 407–16. doi:10.1534/genetics.107.072892. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17603112.  
  27. ^ Papke RT, Zhaxybayeva O, Feil EJ, Sommerfeld K, Muise D, Doolittle WF (2007). "Searching for species in haloarchaea". Proc. Natl. Acad. Sci. U. S. A. 104 (35): 14092–7. doi:10.1073/pnas.0706358104. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17715057.  
  28. ^ Kunin V, Goldovsky L, Darzentas N, Ouzounis CA (2005). "The net of life: reconstructing the microbial phylogenetic network". Genome Res. 15 (7): 954–9. doi:10.1101/gr.3666505. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15965028.  
  29. ^ Robertson CE, Harris JK, Spear JR, Pace NR (2005). "Phylogenetic diversity and ecology of environmental Archaea". Curr. Opin. Microbiol. 8 (6): 638–42. PMID 16236543.  
  30. ^ Hugenholtz P (2002). "Exploring prokaryotic diversity in the genomic era". Genome Biol. 3 (2): REVIEWS0003. doi:10.1186/gb-2002-3-2-reviews0003. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11864374.  
  31. ^ Rappé MS, Giovannoni SJ (2003). "The uncultured microbial majority". Annu. Rev. Microbiol. 57: 369–94. doi:10.1146/annurev.micro.57.030502.090759. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 14527284.  
  32. ^ Huber H, Hohn MJ, Rachel R, Fuchs T, Wimmer VC, Stetter KO. (2002). "A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont. ". Nature 417 (6884): 27 – 8. doi:10.1038/417063a. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11986665.  
  33. ^ Barns SM, Delwiche CF, Palmer JD, Pace NR (1996). "Perspectives on archaeal diversity, thermophily and monophyly from environmental rRNA sequences". Proc. Natl. Acad. Sci. U. S. A. 93 (17): 9188–93. doi:10.1073/pnas.93.17.9188. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 8799176.  
  34. ^ Baker, B. J. , Tyson, G. W. , Webb, R. I. , Flanagan, J. , Hugenholtz, P. and Banfield, J. F. (2006). "Lineages of acidophilic Archaea revealed by community genomic analysis. Science". Science 314 (6884): 1933 – 1935. doi:10.1126/science.1132690. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17185602.  
  35. ^ a b c d Krieg, Noel (2005). Bergey’s Manual® of Systematic Bacteriology. USA: Springer, 21-26. ISBN 978-0-387-24143-2.  
  36. ^ Barns, Sue and Burggraf, Siegfried. (1997) Crenarchaeota. Version 01 January 1997. in The Tree of Life Web Project
  37. ^ Walsby AE (2005). "Archaea with square cells". Trends Microbiol. 13 (5): 193–5. doi:10.1016/j.tim.2005.03.002. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15866034.  
  38. ^ Hixon WG, Searcy DG (1993). "Cytoskeleton in the archaebacterium Thermoplasma acidophilum? Viscosity increase in soluble extracts". BioSystems 29 (2-3): 151–60. doi:10.1016/0303-2647(93)90091-P. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 8374067.  
  39. ^ Hara F, Yamashiro K, Nemoto N, et al (2007). "An actin homolog of the archaeon Thermoplasma acidophilum that retains the ancient characteristics of eukaryotic actin". J. Bacteriol. 189 (5): 2039–45. doi:10.1128/JB.01454-06. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17189356.  
  40. ^ Trent JD, Kagawa HK, Yaoi T, Olle E, Zaluzec NJ (1997). "Chaperonin filaments: the archaeal cytoskeleton?". Proc. Natl. Acad. Sci. U. S. A. 94 (10): 5383–8. doi:10.1073/pnas.94.10.5383. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 9144246.  
  41. ^ Hall-Stoodley L, Costerton JW, Stoodley P (2004). "Bacterial biofilms: from the natural environment to infectious diseases". Nat. Rev. Microbiol. 2 (2): 95–108. doi:10.1038/nrmicro821. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15040259.  
  42. ^ Nickell S, Hegerl R, Baumeister W, Rachel R (2003). "Pyrodictium cannulae enter the periplasmic space but do not enter the cytoplasm, as revealed by cryo-electron tomography". J. Struct. Biol. 141 (1): 34–42. doi:10.1016/S1047-8477(02)00581-6. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 12576018.  
  43. ^ Horn C, Paulmann B, Kerlen G, Junker N, Huber H (1999). "In vivo observation of cell division of anaerobic hyperthermophiles by using a high-intensity dark-field microscope". J. Bacteriol. 181 (16): 5114–8. doi:10.1073/pnas.241636498v1. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10438790.  
  44. ^ De Rosa M, Gambacorta A, Gliozzi A (1986). "Structure, biosynthesis, and physicochemical properties of archaebacterial lipids". Microbiol. Rev. 50 (1): 70–80. PMID 3083222.  
  45. ^ Koga Y, Morii H (2007). "Biosynthesis of ether-type polar lipids in archaea and evolutionary considerations". Microbiol. Mol. Biol. Rev. 71 (1): 97–120. doi:10.1128/MMBR.00033-06. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17347520.  
  46. ^ Sára M, Sleytr UB (2000). "S-Layer proteins". J. Bacteriol. 182 (4): 859–68. doi:10.1128/JB.182.4.859-868.2000. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10648507.  
  47. ^ Howland, John L. (2000) The Surprising Archaea: Discovering Another domain of Life, pages 69-71. (Oxford: Oxford University Press). ISBN 0-19-511183-4.
  48. ^ Thomas NA, Bardy SL, Jarrell KF (2001). "The archaeal flagellum: a different kind of prokaryotic motility structure". FEMS Microbiol. Rev. 25 (2): 147–74. doi:10.1111/j.1574-6976.2001.tb00575.x. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11250034.  
  49. ^ Ng SY, Chaban B, Jarrell KF (2006). "Archaeal flagella, bacterial flagella and type IV pili: a comparison of genes and posttranslational modifications". J. Mol. Microbiol. Biotechnol. 11 (3-5): 167–91. doi:10.1159/000094053. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16983194.  
  50. ^ a b Bernander R (1998). "Archaea and the cell cycle". Mol. Microbiol. 29 (4): 955–61. doi:10.1046/j.1365-2958.1998.00956.x. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 9767564.  
  51. ^ Kelman LM, Kelman Z (2004). "Multiple origins of replication in archaea". Trends Microbiol. 12 (9): 399–401. doi:10.1016/j.tim.2004.07.001. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 153371581.  
  52. ^ Onyenwoke RU, Brill JA, Farahi K, Wiegel J (2004). "Sporulation genes in members of the low G+C Gram-type-positive phylogenetic branch ( Firmicutes)". Arch. Microbiol. 182 (2-3): 182–92. doi:10.1007/s00203-004-0696-y. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15340788.  
  53. ^ Kostrikina NA, Zvyagintseva IS, Duda VI. (1991). "Cytological peculiarities of some extremely halophilic soil archaeobacteria". Arch. Microbiol. 156 (5): 344–49. doi:10.1007/BF00248708. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  54. ^ a b Allers T, Mevarech M (2005). "Archaeal genetics - the third way". Nat. Rev. Genet. 6 (1): 58–73. doi:10.1038/nrg1504. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15630422.  
  55. ^ Baliga NS, Bonneau R, Facciotti MT, et al (2004). "Genome sequence of Haloarcula marismortui: a halophilic archaeon from the Dead Sea". Genome Res. 14 (11): 2221–34. doi:10.1101/gr.2700304. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15520287.  
  56. ^ Waters E, Hohn MJ, Ahel I, et al (2003). "The genome of Nanoarchaeum equitans: insights into early archaeal evolution and derived parasitism". Proc. Natl. Acad. Sci. U. S. A. 100 (22): 12984–8. doi:10.1073/pnas.1735403100. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 14566062.  
  57. ^ Schleper C, Holz I, Janekovic D, Murphy J, Zillig W (1995). "A multicopy plasmid of the extremely thermophilic archaeon Sulfolobus effects its transfer to recipients by mating". J. Bacteriol. 177 (15): 4417–26. PMID 7635827.  
  58. ^ Sota M; Top EM (2008). "Horizontal Gene Transfer Mediated by Plasmids", Plasmids: Current Research and Future Trends. Caister Academic Press. ISBN 978-1-904455-35-6.  
  59. ^ Lipps G (2008). "Archaeal Plasmids", Plasmids: Current Research and Future Trends. Caister Academic Press. ISBN 978-1-904455-35-6.  
  60. ^ Xiang X, Chen L, Huang X, Luo Y, She Q, Huang L (2005). "Sulfolobus tengchongensis spindle-shaped virus STSV1: virus-host interactions and genomic features". J. Virol. 79 (14): 8677–86. doi:10.1128/JVI.79.14.8677-8686.2005. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15994761.  
  61. ^ Prangishvili D, Forterre P, Garrett RA (2006). "Viruses of the Archaea: a unifying view". Nat. Rev. Microbiol. 4 (11): 837–48. doi:10.1038/nrmicro1527. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17041631.  
  62. ^ Prangishvili D, Garrett RA (2004). "Exceptionally diverse morphotypes and genomes of crenarchaeal hyperthermophilic viruses". Biochem. Soc. Trans. 32 (Pt 2): 204–8. doi:10.1042/BST0320204. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15046572.  
  63. ^ Mojica FJ, Díez-Villaseñor C, García-Martínez J, Soria E (2005). "Intervening sequences of regularly spaced prokaryotic repeats derive from foreign genetic elements". J. Mol. Evol. 60 (2): 174–82. doi:10.1007/s00239-004-0046-3. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15791728.  
  64. ^ Makarova KS, Grishin NV, Shabalina SA, Wolf YI, Koonin EV (2006). "A putative RNA-interference-based immune system in prokaryotes: computational analysis of the predicted enzymatic machinery, functional analogies with eukaryotic RNAi, and hypothetical mechanisms of action". Biol. Direct 1: 7. doi:10.1186/1745-6150-1-7. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16545108.  
  65. ^ Graham DE, Overbeek R, Olsen GJ, Woese CR (2000). "An archaeal genomic signature". Proc. Natl. Acad. Sci. U. S. A. 97 (7): 3304–8. doi:10.1073/pnas.050564797. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10716711.  
  66. ^ a b Gaasterland T (1999). "Archaeal genomics". Curr. Opin. Microbiol. 2 (5): 542–7. doi:10.1016/S1369-5274(99)00014-4. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10508726.  
  67. ^ Aravind L, Koonin EV (1999). "DNA-binding proteins and evolution of transcription regulation in the archaea". Nucleic Acids Res. 27 (23): 4658–70. doi:10.1093/nar/27.23.4658. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10556324.  
  68. ^ Eckburg P, Lepp P, Relman D (2003). "Archaea and their potential role in human disease". Infect Immun 71 (2): 591–6. doi:10.1128/IAI.71.2.591-596.2003. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 12540534.  
  69. ^ Cavicchioli R, Curmi P, Saunders N, Thomas T (2003). "Pathogenic archaea: do they exist?". Bioessays 25 (11): 1119–28. doi:10.1002/bies.10354. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 14579252.  
  70. ^ Lepp P, Brinig M, Ouverney C, Palm K, Armitage G, Relman D (2004). "Methanogenic Archaea and human periodontal disease". Proc Natl Acad Sci U S A 101 (16): 6176–81. doi:10.1073/pnas.0308766101. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15067114.  
  71. ^ Eckburg PB, Bik EM, Bernstein CN, et al (2005). "Diversity of the human intestinal microbial flora". Science 308 (5728): 1635–8. doi:10.1126/science.1110591. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15831718.  
  72. ^ Giovannoni SJ, Stingl U. (2005). "Molecular diversity and ecology of microbial plankton". Nature 427 (7057): 343–8. doi:10.1038/nature04158. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16163344.  
  73. ^ Konneke M, Bernhard AE, de la Torre JR, Walker CB, Waterbury JB, Stahl DA. (2005). "Isolation of an autotrophic ammonia-oxidizing marine archaeon". Nature 437 (7057): 543–6. doi:10.1038/nature03911. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16177789.  
  74. ^ Breithaupt H (2001). "The hunt for living gold. The search for organisms in extreme environments yields useful enzymes for industry". EMBO Rep. 2 (11): 968–71. doi:10.1093/embo-reports/kve238. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11713183.  
  75. ^ a b Egorova K, Antranikian G (2005). "Industrial relevance of thermophilic Archaea". Curr. Opin. Microbiol. 8 (6): 649–55. PMID 16257257.  
  76. ^ Synowiecki J, Grzybowska B, Zdziebło A (2006). "Sources, properties and suitability of new thermostable enzymes in food processing". Crit Rev Food Sci Nutr 46 (3): 197–205. doi:10.1080/10408690590957296. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16527752.  
  77. ^ Schiraldi C, Giuliano M, De Rosa M (2002). "Perspectives on biotechnological applications of archaea". Archaea 1 (2): 75–86. PMID 15803645.  
  78. ^ Norris PR, Burton NP, Foulis NA (2000). "Acidophiles in bioreactor mineral processing". Extremophiles 4 (2): 71–6. doi:10.1007/s007920050139. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10805560.  
  79. ^ Shand RF; Leyva KJ (2008). "Archaeal Antimicrobials: An Undiscovered Country", Archaea: New Models for Prokaryotic Biology. Caister Academic Press. ISBN 978-1-904455-27-1.  

Further reading

External links

General

Classification

Genomics


The United States Department of Energy ( DOE) is a Cabinet -level department of the United States government responsible for energy policy The Integrated Microbial Genomes (IMG is a genome browsing and annotation system developed by the DOE- Joint Genome Institute.

Dictionary

archaea

-noun

  1. Plural form of archaeon.
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