Microorganism

A microorganism or microbe is an organism that is microscopic (too small to be visible to the naked eye). Microorganisms are often described as 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.

Microorganisms and unicellular organisms

Microorganisms can be found almost anywhere in the taxonomic organisation of life on the planet. Unicellular organisms carry out all the functions of life. Bacteria and archaea are almost always microscopic, whilst 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 qualification is significant since most multicellular organisms consist of a single cell at the beginning of their life cycles. Unicellular organisms usually contain only a single copy of their genome when not undergoing cell division, although some organisms have multiple cell nuclei (see coenocyte).

Habitats and ecology

Microorganisms are found in virtually every habitat present in nature. Even in hostile environments such as 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 are unusually resistant to radiation. Many types of microorganisms have intimate symbiotic relationships with other larger organisms; some of which are mutually beneficial (mutualism), while others can be damaging to the host organism (parasitism). If microorganisms can cause disease in a host they are known as pathogens.

Importance

Microorganisms are used in brewing, baking and other food-making processes. They are also essential tools in biotechnology and the study of biochemistry, genetics and molecular biology. They can also be harmful as a significant cause of human disease, and some have uses as biological weapons.

Microorganisms have an important place in all ecosystems and in most higher-order multicellular organisms (as symbionts). They are vital to the environment, as they participate in the Earth's element cycles (such as the carbon cycle and nitrogen cycle). They are also involved in the recycling of other organisms' dead remains (see decomposition) and waste products.

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

Microbiology

Gourt Home::Gourt :: Microorganism

Microorganisms and unicellular organisms

Habitats and ecology

Importance

See also

External links