Microorganism

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.

Micro-organisms and unicellular organisms

Micro-organisms may be found almost anywhere in the taxonomic structure. Unicellular organisms carry out all the functions of life. 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).

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.

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.

See also

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

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