A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). Microorganisms are often illustrated using single-celled, or unicellular organisms; however, some unicellular protists are visible to the naked eye, and some multicellular species are microscopic. The study of microorganisms is called microbiology. In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... Typical phyla Rhodophyta (red algae) Chromista Heterokontophyta (heterokonts) Haptophyta Cryptophyta (cryptomonads) Alveolates Dinoflagellata Apicomplexa Ciliophora (ciliates) Excavates Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Amoebozoa Choanozoa Many others; classification varies Protists are a heterogeneous group of living things, comprising those eukaryotes that are neither animals, plants, nor fungi. ... Microbiology (in Greek micron = small and biologia = studying life) is the study of microorganisms, including viruses, prokaryotes and simple eukaryotes. ...

Microorganisms and unicellular organisms

Microorganisms may be found almost anywhere in the taxonomic structure. Bacteria and archaea are almost always microscopic. A number of eukaryotes are also microscopic, including most protists and a number of fungi. Unicellular species are those whose members consist of a single cell throughout their life cycle. This latter qualification is significant since most multicellular organisms consist of a single cell at the beginning of their life cycles. Usually, unicellular organisms contain only a single copy of their genome (except when undergoing cell division), although some organisms have multiple cell nuclei (see coenocyte). Taxonomy (from Greek verb tassein = to classify and nomos = law, science, cf economy) may refer to: the science of classification (see alpha taxonomy) a classification Initially taxonomy was only the science of classifying living organisms, but later the word was applied in a wider sense, and may also refer to... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota The Archaea are a major division of living organisms. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Protista A eukaryote (also spelled eucaryote) is an organism with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Typical phyla Rhodophyta (red algae) Chromista Heterokontophyta (heterokonts) Haptophyta Cryptophyta (cryptomonads) Alveolates Dinoflagellata Apicomplexa Ciliophora (ciliates) Excavates Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Amoebozoa Choanozoa Many others; classification varies Protists are a heterogeneous group of living things, comprising those eukaryotes that are neither animals, plants, nor fungi. ... Divisions Chytridiomycota Zygomycota Glomeromycota Ascomycota Basidiomycota Yellow fungus Fungus growing on a tree in Borneo A fungus (plural fungi) is a eukaryotic organism that digests its food externally and absorbs the nutrient molecules into its cells. ... In biology, the most commonly used definition of species was first coined by Ernst Mayr. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... Multicellular organisms are those organisms containing more than one cell, and having differentiated cells that perform specialized functions. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Cell division is the process by which a cell (called the parent cell) divides into two cells (called daughter cells). ... In cell biology, the nucleus (from Latin nucleus or nuculeus, kernel) is found in all eukaryotic cells that contains most of the cells genetic material. ... A coenocyte is a multinucleate cell. ...

Habitats and ecology

Microorganisms are found everywhere in nature. Even in hostile environments, like the poles, deserts, geysers, rocks, and the deep sea, some types of microorganisms have adapted to the extreme conditions and sustained colonies; these organisms are known as extremophiles. Some extremophiles have been known to survive for a prolonged time in a vacuum, and some can be unusually resistant to radiation. Microorganisms are used in brewing, baking, biotechnology, recycling of other organisms' remains and waste products, and many other processes. They can also be harmful as pathogens when, as parasites, they cause infections. A dune in the Egyptian desert Desert in California In geography, a desert is a landscape form or region that receives little precipitation - less than 250 mm per year. ... Clepsydra Geyser in Yellowstone A geyser is a type of hot spring that erupts periodically, ejecting a column of hot water and steam into the air. ... Our earth is composed of three main types of rock, each having been formed in its own special way. ... An extremophile is an organism, usually unicellular, which thrives in or requires extreme conditions. ... For other uses, see vacuum cleaner and Vacuum (musical group). ... Radiation has a variety of different meanings. ... The Brewer, designed and engraved, in the Sixteenth. ... Wikibooks Cookbook has more about this subject: Baking Baking is the technique of cooking food in an oven by dry heat applied evenly throughout the oven. ... Biotechnology is technology based on biology, especially when used in agriculture, food science, and medicine. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. ... An infection is the detrimental colonization of a host organism by a foreign species. ...

Microorganisms have an important place in all ecosystems and in most higher-order multicellular organisms. For mankind they are important because they participate in the earth's element cycles (such as the Carbon cycle), and because of their use in the creation of certain types of food, medicines and biological weapons. In ecology, an ecosystem is a community of organisms (plant, animal and other living organisms - also referred as biocenose) together with their environment (or biotope), functioning as a unit. ... The carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the Earth. ... A medication is a licenced drug taken to cure or reduce symptoms of an illness or medical condition. ... Biological warfare, also known as germ warfare, is the use of any organism (bacteria, virus or other disease_causing organism) or toxin found in nature, as a weapon of war. ...

See also

• Biology
• Microbiology
• Microscope
• Prokaryote
• Eukaryote
• Archaea
• Cell
• Nanobacterium

Main articles: Life The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor... Microbiology (in Greek micron = small and biologia = studying life) is the study of microorganisms, including viruses, prokaryotes and simple eukaryotes. ... 1852 microscope Compound microscope made by John Cuff in 1750 A microscope (Greek: micron = small and scopos = aim) is an instrument for viewing objects that are too small to be seen by the naked or unaided eye. ... Prokaryotes (from Old Greek pro- before + karyon nut, referring to the cell nucleus, + suffix -otos, pl. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Protista A eukaryote (also spelled eucaryote) is an organism with complex cells, in which the genetic material is organized into membrane-bound nuclei. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota The Archaea are a major division of living organisms. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... Structures found on meteorite fragment ALH84001 Nanobacteria are said to be cell walled microorganisms with a diameter well below the generally accepted lower limit (about 200 nanometres) for bacteria. ...

External links

• Microbe News from Genome News Network
• BBC News, 28 September, 2001: The microbes that 'rule the world' Citat: "... The Earth's climate may be dependent upon microbes that eat rock beneath the sea floor, according to new research....The number of the worm-like tracks in the rocks diminishes with depth; at 300 metres (985 feet) below the sea floor, they become much rarer..."
• BBC News, 10 July, 2000, Snow microbes found at South Pole Citat: "...able to survive the large doses of ultraviolet radiation, extreme cold and darkness...The microbes have DNA sequences similar to a category of bacteria known as Deinococcus..."
• BBCNews: 16 January, 2002, Tough bugs point to life on Mars Citat: "...This research demonstrates that certain microbes can thrive in the absence of sunlight by using hydrogen gas..."
• BBCNews: 17 January, 2002, Alien life could be like Antarctic bugs
• Microbiology