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Hydrothermal Vents: Hot springs on the ocean floor. They are commonly found near volcanically active places such as mid-oceanic ridges.Polychaeta: A class of marine annelids including sandworms, tube worms, clamworms, and fire worms. It includes also the genus Myxicola infundibulum.Pacific OceanEpsilonproteobacteria: A group of proteobacteria consisting of chemoorganotrophs usually associated with the DIGESTIVE SYSTEM of humans and animals.Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Mytilidae: A family of marine MUSSELS in the class BIVALVIA.Decapoda (Crustacea): The largest order of CRUSTACEA, comprising over 10,000 species. They are characterized by three pairs of thoracic appendages modified as maxillipeds, and five pairs of thoracic legs. The order includes the familiar shrimps, crayfish (ASTACOIDEA), true crabs (BRACHYURA), and lobsters (NEPHROPIDAE and PALINURIDAE), among others.Chemoautotrophic Growth: Growth of organisms using AUTOTROPHIC PROCESSES for obtaining nutrients and chemotrophic processes for obtaining a primary energy supply. Chemotrophic processes are involved in deriving a primary energy supply from exogenous chemical sources. Chemotrophic autotrophs (chemoautotrophs) generally use inorganic chemicals as energy sources and as such are called chemolithoautotrophs. Most chemoautotrophs live in hostile environments, such as deep sea vents. They are mostly BACTERIA and ARCHAEA, and are the primary producers for those ecosystems.Atlantic OceanGastropoda: A class in the phylum MOLLUSCA comprised of SNAILS and slugs. The former have coiled external shells and the latter usually lack shells.Volcanic Eruptions: The ash, dust, gases, and lava released by volcanic explosion. The gases are volatile matter composed principally of about 90% water vapor, and carbon dioxide, sulfur dioxide, hydrogen, carbon monoxide, and nitrogen. The ash or dust is pyroclastic ejecta and lava is molten extrusive material consisting mainly of magnesium silicate. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Oceans and Seas: A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).DNA, Archaeal: Deoxyribonucleic acid that makes up the genetic material of archaea.RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Bivalvia: A class in the phylum MOLLUSCA comprised of mussels; clams; OYSTERS; COCKLES; and SCALLOPS. They are characterized by a bilaterally symmetrical hinged shell and a muscular foot used for burrowing and anchoring.Marine Biology: The study of the origin, structure, development, growth, function, genetics, and reproduction of organisms which inhabit the OCEANS AND SEAS.Symbiosis: The relationship between two different species of organisms that are interdependent; each gains benefits from the other or a relationship between different species where both of the organisms in question benefit from the presence of the other.Thermococcales: An order of strictly anaerobic, thermophilic archaea, in the kingdom EURYARCHAEOTA. Members exhibit heterotropic growth by sulfur respiration. There is a single family THERMOCOCCACEAE.DNA, Ribosomal: DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.Annelida: A phylum of metazoan invertebrates comprising the segmented worms, and including marine annelids (POLYCHAETA), freshwater annelids, earthworms (OLIGOCHAETA), and LEECHES. Only the leeches are of medical interest. (Dorland, 27th ed)Gammaproteobacteria: A group of the proteobacteria comprised of facultatively anaerobic and fermentative gram-negative bacteria.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.Gram-Negative Chemolithotrophic Bacteria: A large group of bacteria including those which oxidize ammonia or nitrite, metabolize sulfur and sulfur compounds, or deposit iron and/or manganese oxides.Hot Temperature: Presence of warmth or heat or a temperature notably higher than an accustomed norm.Water Microbiology: The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.Thermococcus: A genus of extremely thermophilic heterotrophic archaea, in the family THERMOCOCCACEAE, occurring in heated sea flows. They are anaerobic chemoorganotropic sulfidogens.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.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.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.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)Base Composition: The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.Gills: Paired respiratory organs of fishes and some amphibians that are analogous to lungs. They are richly supplied with blood vessels by which oxygen and carbon dioxide are exchanged directly with the environment.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.Sulfides: Chemical groups containing the covalent sulfur bonds -S-. The sulfur atom can be bound to inorganic or organic moieties.Piscirickettsiaceae: A family of gram-negative bacteria, in the order Thiotrichales.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)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.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.Bacterial Physiological Phenomena: Physiological processes and properties of BACTERIA.Carbon Cycle: The cycle by which the element carbon is exchanged between organic matter and the earth's physical environment.Indian Ocean: A body of water covering approximately one-fifth of the total ocean area of the earth, extending amidst Africa in the west, Australia in the east, Asia in the north, and Antarctica in the south. Including the Red Sea and the Persian Gulf, it constitutes the third largest ocean after the ATLANTIC OCEAN and the PACIFIC OCEAN. (New Encyclopaedia Britannica Micropaedia, 15th ed, 1990, p289)Geological Phenomena: The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.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.Anomura: An infraorder of CRUSTACEA, in the order DECAPODA comprising the hermit crabs and characterized by a small fifth pair of legs.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.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.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)Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Deltaproteobacteria: A group of PROTEOBACTERIA represented by morphologically diverse, anaerobic sulfidogens. Some members of this group are considered bacterial predators, having bacteriolytic properties.Gram-Negative Anaerobic Bacteria: A large group of anaerobic bacteria which show up as pink (negative) when treated by the Gram-staining method.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.Geology: The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Reproductive Physiological Phenomena: Physiological processes, factors, properties and characteristics pertaining to REPRODUCTION.Thiosulfates: Inorganic salts of thiosulfuric acid possessing the general formula R2S2O3.Antarctic Regions: The continent lying around the South Pole and the southern waters of the Atlantic, Pacific, and Indian Oceans. It includes the Falkland Islands Dependencies. (From Webster's New Geographical Dictionary, 1988, p55)Mid-Atlantic Region: A geographical area of the United States comprising the District of Columbia, Delaware, Maryland, New Jersey, New York, and Pennsylvania.Tellurium: Tellurium. An element that is a member of the chalcogen family. It has the atomic symbol Te, atomic number 52, and atomic weight 127.60. It has been used as a coloring agent and in the manufacture of electrical equipment. Exposure may cause nausea, vomiting, and CNS depression.Invertebrates: Animals that have no spinal column.RNA, Archaeal: Ribonucleic acid in archaea having regulatory and catalytic roles as well as involvement in protein synthesis.Geography: The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)RNA, Bacterial: Ribonucleic acid in bacteria having regulatory and catalytic roles as well as involvement in protein synthesis.Biogenesis: The origin of life. It includes studies of the potential basis for life in organic compounds but excludes studies of the development of altered forms of life through mutation and natural selection, which is BIOLOGICAL EVOLUTION.Sulfate Adenylyltransferase: An enzyme that catalyzes the activation of sulfate ions by ATP to form adenosine-5'-phosphosulfate and pyrophosphate. This reaction constitutes the first enzymatic step in sulfate utilization following the uptake of sulfate. EC 2.7.7.4.Mollusca: A phylum of the kingdom Metazoa. Mollusca have soft, unsegmented bodies with an anterior head, a dorsal visceral mass, and a ventral foot. Most are encased in a protective calcareous shell. It includes the classes GASTROPODA; BIVALVIA; CEPHALOPODA; Aplacophora; Scaphopoda; Polyplacophora; and Monoplacophora.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.Aquatic Organisms: Organisms that live in water.Hydrogen: The first chemical element in the periodic table. It has the atomic symbol H, atomic number 1, and atomic weight [1.00784; 1.00811]. It exists, under normal conditions, as a colorless, odorless, tasteless, diatomic gas. Hydrogen ions are PROTONS. Besides the common H1 isotope, hydrogen exists as the stable isotope DEUTERIUM and the unstable, radioactive isotope TRITIUM.Bacteria, AnaerobicCarbon: A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.GreeceOxidation-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).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)Hydrostatic Pressure: The pressure due to the weight of fluid.Crustacea: A large subphylum of mostly marine ARTHROPODS containing over 42,000 species. They include familiar arthropods such as lobsters (NEPHROPIDAE), crabs (BRACHYURA), shrimp (PENAEIDAE), and barnacles (THORACICA).Genes, Archaeal: The functional genetic units of ARCHAEA.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.Genome, Archaeal: The genetic complement of an archaeal organism (ARCHAEA) as represented in its DNA.Nitrates: Inorganic or organic salts and esters of nitric acid. These compounds contain the NO3- radical.RNA, Ribosomal, 18S: Constituent of the 40S subunit of eukaryotic ribosomes. 18S rRNA is involved in the initiation of polypeptide synthesis in eukaryotes.