Archaea: One of the three domains of life (the others being BACTERIA and Eukarya), formerly called Archaebacteria under the taxon Bacteria, but now considered separate and distinct. They are characterized by: (1) the presence of characteristic tRNAs and ribosomal RNAs; (2) the absence of peptidoglycan cell walls; (3) the presence of ether-linked lipids built from branched-chain subunits; and (4) their occurrence in unusual habitats. While archaea resemble bacteria in morphology and genomic organization, they resemble eukarya in their method of genomic replication. The domain contains at least four kingdoms: CRENARCHAEOTA; EURYARCHAEOTA; NANOARCHAEOTA; and KORARCHAEOTA.Archaeal Proteins: Proteins found in any species of archaeon.Genes, Archaeal: The functional genetic units of ARCHAEA.DNA, Archaeal: Deoxyribonucleic acid that makes up the genetic material of archaea.RNA, Archaeal: Ribonucleic acid in archaea having regulatory and catalytic roles as well as involvement in protein synthesis.Genome, Archaeal: The genetic complement of an archaeal organism (ARCHAEA) as represented in its DNA.Crenarchaeota: A kingdom in the domain ARCHAEA comprised of thermoacidophilic, sulfur-dependent organisms. The two orders are SULFOLOBALES and THERMOPROTEALES.Gene Expression Regulation, Archaeal: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in archaea.Haloferax volcanii: A species of halophilic archaea found in the Dead Sea.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Methane: The simplest saturated hydrocarbon. It is a colorless, flammable gas, slightly soluble in water. It is one of the chief constituents of natural gas and is formed in the decomposition of organic matter. (Grant & Hackh's Chemical Dictionary, 5th ed)Methanococcus: A genus of anaerobic coccoid METHANOCOCCACEAE whose organisms are motile by means of polar tufts of flagella. These methanogens are found in salt marshes, marine and estuarine sediments, and the intestinal tract of animals.Bacteria: One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.Sulfolobus: A genus of aerobic, chemolithotrophic, coccoid ARCHAEA whose organisms are thermoacidophilic. Its cells are highly irregular in shape, often lobed, but occasionally spherical. It has worldwide distribution with organisms isolated from hot acidic soils and water. Sulfur is used as an energy source.Methanobacteriaceae: A family of anaerobic, coccoid to rod-shaped METHANOBACTERIALES. Cell membranes are composed mainly of polyisoprenoid hydrocarbons ether-linked to glycerol. Its organisms are found in anaerobic habitats throughout nature.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Euryarchaeota: A phylum of ARCHAEA comprising at least seven classes: Methanobacteria, Methanococci, Halobacteria (extreme halophiles), Archaeoglobi (sulfate-reducing species), Methanopyri, and the thermophiles: Thermoplasmata, and Thermococci.Methanosarcina: A genus of anaerobic, irregular spheroid-shaped METHANOSARCINALES whose organisms are nonmotile. Endospores are not formed. These archaea derive energy via formation of methane from acetate, methanol, mono-, di-, and trimethylamine, and possibly, carbon monoxide. Organisms are isolated from freshwater and marine environments.Nitrification: A process facilitated by specialized bacteria involving the oxidation of ammonium to nitrite and nitrate.Methanobacterium: A genus of anaerobic, rod-shaped METHANOBACTERIACEAE. Its organisms are nonmotile and use ammonia as the sole source of nitrogen. These methanogens are found in aquatic sediments, soil, sewage, and the gastrointestinal tract of animals.Desulfurococcaceae: A family of archaea, in the order DESULFUROCOCCALES, consisting of anaerobic cocci which utilize peptides, proteins or carbohydrates facultatively by sulfur respiration or fermentation. There are eight genera: AEROPYRUM, Desulfurococcus, Ignicoccus, Staphylothermus, Stetteria, Sulfophoboccus, Thermodiscus, and Thermosphaera. (From Bergey's Manual of Systematic Bacteriology, 2d ed)Methanosarcinales: An order of anaerobic methanogens in the kingdom EURYARCHAEOTA. There are two families: METHANOSARCINACEAE and Methanosaetaceae.Halobacteriales: An order of extremely halophilic archaea, in the kingdom EURYARCHAEOTA. They occur ubiquitously in nature where the salt concentration is high, and are chemoorganotrophic, using amino acids or carbohydrates as a carbon source.Haloferax: A genus of extremely halophilic HALOBACTERIACEAE which are chemoheterotropic and strictly aerobic. They are found in neutral saline environments such as salt lakes (especially the Dead Sea) and marine salterns.Pyrococcus: A genus of strictly anaerobic ultrathermophilic archaea, in the family THERMOCOCCACEAE, occurring in heated seawaters. They exhibit heterotrophic growth at an optimum temperature of 100 degrees C.Sulfolobus acidocaldarius: A species of aerobic, chemolithotrophic ARCHAEA consisting of coccoid cells that utilize sulfur as an energy source. The optimum temperature for growth is 70-75 degrees C. They are isolated from acidic fields.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Methanosarcinaceae: A family of anaerobic METHANOSARCINALES whose cells are mesophilic or thermophilic and appear as irregular spheroid bodies or sheathed rods. These methanogens are found in any anaerobic environment including aquatic sediments, anaerobic sewage digesters and gastrointestinal tracts. There are four genera: METHANOSARCINA, Methanolobus, Methanothrix, and Methanococcoides.Pyrococcus abyssi: A species of gram-negative hyperthermophilic ARCHAEA found in deep ocean hydrothermal vents. It is an obligate anaerobe and obligate chemoorganotroph.Chromosomes, Archaeal: Structures within the nucleus of archaeal cells consisting of or containing DNA, which carry genetic information essential to the cell.Sulfolobus solfataricus: A species of thermoacidophilic ARCHAEA in the family Sulfolobaceae, found in volcanic areas where the temperature is about 80 degrees C and SULFUR is present.Geologic Sediments: A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)Methanococcales: An order of anaerobic methanogens in the kingdom EURYARCHAEOTA. They are pseudosarcina, coccoid or sheathed rod-shaped and catabolize methyl groups. The cell wall is composed of protein. The order includes one family, METHANOCOCCACEAE. (From Bergey's Manual of Systemic Bacteriology, 1989)Archaeoglobus fulgidus: A species of extremely thermophilic, sulfur-reducing archaea. It grows at a maximum temperature of 95 degrees C. in marine or deep-sea geothermal areas.Pyrococcus furiosus: A species of strictly anaerobic, hyperthermophilic archaea which lives in geothermally-heated marine sediments. It exhibits heterotropic growth by fermentation or sulfur respiration.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Thermococcus: A genus of extremely thermophilic heterotrophic archaea, in the family THERMOCOCCACEAE, occurring in heated sea flows. They are anaerobic chemoorganotropic sulfidogens.Eukaryotic Cells: Cells of the higher organisms, containing a true nucleus bounded by a nuclear membrane.Methanosarcina barkeri: A species of halophilic archaea whose organisms are nonmotile. Habitats include freshwater and marine mud, animal-waste lagoons, and the rumens of ungulates.Halobacteriaceae: A family of extremely halophilic archaea found in environments with high salt concentrations, such as salt lakes, evaporated brines, or salted fish. Halobacteriaceae are either obligate aerobes or facultative anaerobes and are divided into at least twenty-six genera including: HALOARCULA; HALOBACTERIUM; HALOCOCCUS; HALOFERAX; HALORUBRUM; NATRONOBACTERIUM; and NATRONOCOCCUS.Ammonia: A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Archaeal Viruses: Viruses whose hosts are in the domain ARCHAEA.Glyceryl Ethers: Compounds in which one or more of the three hydroxyl groups of glycerol are in ethereal linkage with a saturated or unsaturated aliphatic alcohol; one or two of the hydroxyl groups of glycerol may be esterified. These compounds have been found in various animal tissue.Eukaryota: One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.Thermoplasma: A genus of facultatively anaerobic heterotrophic archaea, in the order THERMOPLASMALES, isolated from self-heating coal refuse piles and acid hot springs. They are thermophilic and can grow both with and without sulfur.Sequence Alignment: The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.DNA, Ribosomal: DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Autotrophic Processes: The processes by which organisms use simple inorganic substances such as gaseous or dissolved carbon dioxide and inorganic nitrogen as nutrient sources. Contrasts with heterotrophic processes which make use of organic materials as the nutrient supply source. Autotrophs can be either chemoautotrophs (or chemolithotrophs), largely ARCHAEA and BACTERIA, which also use simple inorganic substances for their metabolic energy reguirements; or photoautotrophs (or photolithotrophs), such as PLANTS and CYANOBACTERIA, which derive their energy from light. Depending on environmental conditions some organisms can switch between different nutritional modes (autotrophy; HETEROTROPHY; chemotrophy; or PHOTOTROPHY) to utilize different sources to meet their nutrient and energy requirements.Haloferax mediterranei: A species of halophilic archaea found in the Mediterranean Sea. It produces bacteriocins active against a range of other halobacteria.Prokaryotic Cells: Cells lacking a nuclear membrane so that the nuclear material is either scattered in the cytoplasm or collected in a nucleoid region.Thermoproteaceae: A family of THERMOPROTEALES consisting of variable length rigid rods without septa. They grow either chemolithoautotrophically or by sulfur respiration. The four genera are: PYROBACULUM; THERMOPROTEUS; Caldivirga; and Thermocladium. (From Bergey's Manual of Systematic Bacteriology, 2d ed)Halobacterium salinarum: A species of halophilic archaea found in salt lakes. Some strains form a PURPLE MEMBRANE under anaerobic conditions.Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Thermoplasmales: An order of aerobic, thermophilic archaea, in the kingdom EURYARCHAEOTA, characterized by the absence of a cell wall. Two genera have been described: THERMOPLASMA and Picrophilus.Gene Transfer, Horizontal: The naturally occurring transmission of genetic information between organisms, related or unrelated, circumventing parent-to-offspring transmission. Horizontal gene transfer may occur via a variety of naturally occurring processes such as GENETIC CONJUGATION; GENETIC TRANSDUCTION; and TRANSFECTION. It may result in a change of the recipient organism's genetic composition (TRANSFORMATION, GENETIC).Methanobrevibacter: A genus of gram-positive, anaerobic, cocci to short rod-shaped ARCHAEA, in the family METHANOBACTERIACEAE, order METHANOBACTERIALES. They are found in the GASTROINTESTINAL TRACT or other anoxic environments.Bacterial Proteins: Proteins found in any species of bacterium.Haloarcula marismortui: A species of halophilic archaea distinguished by its production of acid from sugar. This species was previously called Halobacterium marismortui.Genes, rRNA: Genes, found in both prokaryotes and eukaryotes, which are transcribed to produce the RNA which is incorporated into RIBOSOMES. Prokaryotic rRNA genes are usually found in OPERONS dispersed throughout the GENOME, whereas eukaryotic rRNA genes are clustered, multicistronic transcriptional units.Genome, Bacterial: The genetic complement of a BACTERIA as represented in its DNA.Sulfolobales: An order of CRENARCHAEOTA consisting of aerobic or facultatively aerobic, chemolithotrophic cocci which are extreme thermoacidophiles. They lack peptidoglycan in their cell walls.Oxidoreductases: The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.Methanomicrobiaceae: A family of anaerobic METHANOMICROBIALES whose cells are coccoid to straight or slightly curved rods. There are six genera.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Archaeoglobus: A genus of extremely thermophilic, sulfate-reducing archaea, in the family Archaeoglobaceae.Anaerobiosis: The complete absence, or (loosely) the paucity, of gaseous or dissolved elemental oxygen in a given place or environment. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)RNA, Transfer: The small RNA molecules, 73-80 nucleotides long, that function during translation (TRANSLATION, GENETIC) to align AMINO ACIDS at the RIBOSOMES in a sequence determined by the mRNA (RNA, MESSENGER). There are about 30 different transfer RNAs. Each recognizes a specific CODON set on the mRNA through its own ANTICODON and as aminoacyl tRNAs (RNA, TRANSFER, AMINO ACYL), each carries a specific amino acid to the ribosome to add to the elongating peptide chains.Conserved Sequence: A sequence of amino acids in a polypeptide or of nucleotides in DNA or RNA that is similar across multiple species. A known set of conserved sequences is represented by a CONSENSUS SEQUENCE. AMINO ACID MOTIFS are often composed of conserved sequences.Salinity: Degree of saltiness, which is largely the OSMOLAR CONCENTRATION of SODIUM CHLORIDE plus any other SALTS present. It is an ecological factor of considerable importance, influencing the types of organisms that live in an ENVIRONMENT.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Soil Microbiology: The presence of bacteria, viruses, and fungi in the soil. This term is not restricted to pathogenic organisms.Plankton: Community of tiny aquatic PLANTS and ANIMALS, and photosynthetic BACTERIA, that are either free-floating or suspended in the water, with little or no power of locomotion. They are divided into PHYTOPLANKTON and ZOOPLANKTON.Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).RNA, Bacterial: Ribonucleic acid in bacteria having regulatory and catalytic roles as well as involvement in protein synthesis.Ribosome Subunits, Large, Archaeal: The large subunit of the archaeal 70s ribosome. It is composed of the 23S RIBOSOMAL RNA, the 5S RIBOSOMAL RNA, and about 40 different RIBOSOMAL PROTEINS.Sulfolobaceae: A family of SULFOLOBALES consisting of aerobic or facultatively anaerobic chemolithotrophic cocci, usually occurring singly. They grow best at a pH of about 2.Bioreactors: Tools or devices for generating products using the synthetic or chemical conversion capacity of a biological system. They can be classical fermentors, cell culture perfusion systems, or enzyme bioreactors. For production of proteins or enzymes, recombinant microorganisms such as bacteria, mammalian cells, or insect or plant cells are usually chosen.Hot Temperature: Presence of warmth or heat or a temperature notably higher than an accustomed norm.Hydrothermal Vents: Hot springs on the ocean floor. They are commonly found near volcanically active places such as mid-oceanic ridges.Protein Structure, Tertiary: The level of protein structure in which combinations of secondary protein structures (alpha helices, beta sheets, loop regions, and motifs) pack together to form folded shapes called domains. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Small proteins usually consist of only one domain but larger proteins may contain a number of domains connected by segments of polypeptide chain which lack regular secondary structure.Proteobacteria: A phylum of bacteria consisting of the purple bacteria and their relatives which form a branch of the eubacterial tree. This group of predominantly gram-negative bacteria is classified based on homology of equivalent nucleotide sequences of 16S ribosomal RNA or by hybridization of ribosomal RNA or DNA with 16S and 23S ribosomal RNA.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Pacific OceanGenes, Bacterial: The functional hereditary units of BACTERIA.Deltaproteobacteria: A group of PROTEOBACTERIA represented by morphologically diverse, anaerobic sulfidogens. Some members of this group are considered bacterial predators, having bacteriolytic properties.Biota: The spectrum of different living organisms inhabiting a particular region, habitat, or biotope.Sulfur: An element that is a member of the chalcogen family. It has an atomic symbol S, atomic number 16, and atomic weight [32.059; 32.076]. It is found in the amino acids cysteine and methionine.Haloarcula: A genus of HALOBACTERIACEAE distinguished from other genera in the family by the presence of specific derivatives of TGD-2 polar lipids. Haloarcula are found in neutral saline environments such as salt lakes, marine salterns, and saline soils.Microbial Consortia: A group of different species of microorganisms that act together as a community.Metagenomics: The genomic analysis of assemblages of organisms.Hot Springs: Habitat of hot water naturally heated by underlying geologic processes. Surface hot springs have been used for BALNEOLOGY. Underwater hot springs are called HYDROTHERMAL VENTS.Bacterial Physiological Phenomena: Physiological processes and properties of BACTERIA.Sulfur-Reducing Bacteria: A group of gram-negative, anaerobic bacteria that is able to oxidize acetate completely to carbon dioxide using elemental sulfur as the electron acceptor.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Estuaries: A partially enclosed body of water, and its surrounding coastal habitats, where saltwater from the ocean mixes with fresh water from rivers or streams. The resulting mixture of seawater and fresh water is called brackish water and its salinity can range from 0.5 to 35 ppt. (accessed A kingdom of hyperthermophilic ARCHAEA found in diverse environments.Pyrococcus horikoshii: Anaerobic hyperthermophilic species of ARCHAEA, isolated from hydrothermal fluid samples. It is obligately heterotrophic with coccoid cells that require TRYPTOPHAN for growth.Methanomicrobiales: An order of anaerobic, highly specialized methanogens, in the kingdom EURYARCHAEOTA. Its organisms are nonmotile or motile, with cells occurring as coccoid bodies, pseudosarcina, or rods. Families include METHANOMICROBIACEAE, Methanocorpusculaceae, and Methanospirillaceae.Pyrobaculum: A genus of rod-shaped, almost rectangular ARCHAEA, in the family THERMOPROTEACEAE. Organisms are facultatively aerobic or strictly anaerobic, grow on various organic substrates, and are found in continental solfataras.Lakes: Inland bodies of still or slowly moving FRESH WATER or salt water, larger than a pond, and supplied by RIVERS and streams.Crystallography, X-Ray: The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Thermoproteus: A genus of obligately anaerobic ARCHAEA, in the family THERMOPROTEACEAE. They are found in acidic hot springs and water holes.Aeropyrum: A genus of anaerobic, chemolithotropic coccoid ARCHAEA, in the family DESULFUROCOCCACEAE. They live in marine environments.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Nucleic Acid Conformation: The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.Heterotrophic Processes: The processes by which organisms utilize organic substances as their nutrient sources. Contrasts with AUTOTROPHIC PROCESSES which make use of simple inorganic substances as the nutrient supply source. Heterotrophs can be either chemoheterotrophs (or chemoorganotrophs) which also require organic substances such as glucose for their primary metabolic energy requirements, or photoheterotrophs (or photoorganotrophs) which derive their primary energy requirements from light. Depending on environmental conditions some organisms can switch between different nutritional modes (AUTOTROPHY; heterotrophy; chemotrophy; or PHOTOTROPHY) to utilize different sources to meet their nutrients and energy requirements.