Microorganism facts for kids

A cluster of Escherichia coli bacteria magnified 10,000 times.

A micro-organism or microbe is an organism which is microscopic, which means so small that people cannot see them with naked eye. The study of microorganisms is called microbiology.

Micro-organisms include bacteria, fungi, archaea, protists and viruses, and are among the earliest known life forms. The first of these four types of micro-organisms may either be free-living or parasitic. Viruses can only be parasitic, since they always reproduce inside other living things.

Most micro-organisms are unicellular organism with only one cell, but there are unicellular protists that are visible to the human eye, and some multicellular species are microscopic.

Micro-organisms live almost everywhere on earth where there is liquid water, including hot springs on the ocean floor and deep inside rocks within the earth's crust. Such habitats are lived in by extremophiles.

Microbes are important in human culture and health in many ways, serving to ferment foods and treat sewage, and to produce fuel, enzymes, and other bioactive compounds. Microbes are essential tools in biology as model organisms and have been put to use in biological warfare and bioterrorism. Microbes are a vital component of fertile soil. In the human body, microorganisms make up the human microbiota, including the essential gut flora. The pathogens responsible for many infectious diseases are microbes and, as such, are the target of hygiene measures.

Classification and structure

Microorganisms can be found almost anywhere on Earth. Bacteria and archaea are almost always microscopic, while a number of eukaryotes are also microscopic, including most protists, some fungi, as well as some micro-animals and plants. Viruses are generally regarded as not living and therefore not considered to be microorganisms, although a subfield of microbiology is virology, the study of viruses.

Free-living micro-organisms

Free-living microbes get their energy in many different ways. Some use photosynthesis, like plants do. Some break down natural chemicals in their environment. Others feed on things that were once living, such as fallen leaves and dead animals, causing them to breakdown or decay. Some fungi and bacteria cause food to decay. Moldy bread or fruit, sour milk, and rotten meat are examples of decayed food. In nature, decayed materials mix with soil, providing essential nutrients for plants to use. Without this process, the nutrients in the soil would run out. These types of organisms are called decomposers. They are the natural recyclers of living things on our planet.

Microbes also help us make some of our foods, such as bread, cheese, yogurt, beer, and wine. They feed on the sugar in grain, fruit, or milk, giving these foods a special texture and taste.

Parasitic microbes

Some microbes, often called germs, cause illness or disease. They are parasites which live by invading living things. Chickenpox, mumps, and measles are all caused by viruses. Some bacteria are also germs. They cause many infectious diseases including tuberculosis and tetanus. Certain bacteria cause tooth decay. It is possible to protect humans against some harmful microbes by storing and preparing food properly, cleaning the teeth, washing hands, and by avoiding close contact with ill people.

Applications

Microorganisms are useful in producing foods, treating waste water, creating biofuels and a wide range of chemicals and enzymes. They are invaluable in research as model organisms. They have been weaponised and sometimes used in warfare and bioterrorism. They are vital to agriculture through their roles in maintaining soil fertility and in decomposing organic matter. They also have applications in aquaculture, such as in biofloc technology.

Food production

Microorganisms are used in a fermentation process to make yoghurt, cheese, curd, kefir, ayran, xynogala, and other types of food. Fermentation cultures provide flavour and aroma, and inhibit undesirable organisms. They are used to leaven bread, and to convert sugars to alcohol in wine and beer. Microorganisms are used in brewing, wine making, baking, pickling and other food-making processes.

Water treatment

Wastewater treatment plants rely largely on microorganisms to oxidise organic matter.

These depend for their ability to clean up water contaminated with organic material on microorganisms that can respire dissolved substances. Respiration may be aerobic, with a well-oxygenated filter bed such as a slow sand filter. Anaerobic digestion by methanogens generate useful methane gas as a by-product.'''''

Energy

Microorganisms are used in fermentation to produce ethanol, and in biogas reactors to produce methane. Scientists are researching the use of algae to produce liquid fuels, and bacteria to convert various forms of agricultural and urban waste into usable fuels.

Chemicals, enzymes

Microorganisms are used to produce many commercial and industrial chemicals, enzymes and other bioactive molecules. Organic acids produced on a large industrial scale by microbial fermentation include acetic acid produced by acetic acid bacteria such as Acetobacter aceti, butyric acid made by the bacterium Clostridium butyricum, lactic acid made by Lactobacillus and other lactic acid bacteria, and citric acid produced by the mould fungus Aspergillus niger.

Microorganisms are used to prepare bioactive molecules such as Streptokinase from the bacterium Streptococcus, Cyclosporin A from the ascomycete fungus Tolypocladium inflatum, and statins produced by the yeast Monascus purpureus.

Science

A laboratory fermentation vessel

Microorganisms are essential tools in biotechnology, biochemistry, genetics, and molecular biology. The yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe are important model organisms in science, since they are simple eukaryotes that can be grown rapidly in large numbers and are easily manipulated. They are particularly valuable in genetics, genomics and proteomics. Microorganisms can be harnessed for uses such as creating steroids and treating skin diseases. Scientists are also considering using microorganisms for living fuel cells, and as a solution for pollution.

Soil

Microbes can make nutrients and minerals in the soil available to plants, produce hormones that spur growth, stimulate the plant immune system and trigger or dampen stress responses. In general a more diverse set of soil microbes results in fewer plant diseases and higher yield.

Human health

All animals seem to have bacteria and protozoa living in or on them without doing much harm. Sometimes, as with herbivores, the microorganisms are vital to the digestion of food. The human gut has more organisms living inside it than there are cells in the human body.

The microorganisms that make up the gut flora in the gastrointestinal tract contribute to gut immunity, synthesize vitamins such as folic acid and biotin, and ferment complex indigestible carbohydrates. Some microorganisms that are seen to be beneficial to health are termed probiotics and are available as dietary supplements, or food additives.

Images for kids

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  Antonie van Leeuwenhoek was the first to study microscopic organisms.

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  Lazzaro Spallanzani showed that boiling a broth stopped it from decaying.

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  Louis Pasteur showed that Spallanzani's findings held even if air could enter through a filter that kept particles out.

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  Robert Koch showed that microorganisms caused disease.

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  Staphylococcus aureus bacteria magnified about 10,000x

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  Euglena mutabilis, a photosynthetic flagellate

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  A tetrad of Deinococcus radiodurans, a radioresistant extremophile bacterium

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  The photosynthetic cyanobacterium Hyella caespitosa (round shapes) with fungal hyphae (translucent threads) in the lichen Pyrenocollema halodytes

See also

In Spanish: Microorganismo para niños