Microorganism facts for kids

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

A microorganism or microbe is a tiny living thing. They are so small you need a microscope to see them! The study of these tiny creatures is called microbiology.

Microorganisms include bacteria, fungi, archaea, protists, and viruses. They are some of the earliest known life forms on Earth. Bacteria, fungi, archaea, and protists can live on their own or as parasites. Viruses, however, can only live and reproduce inside other living things.

Most microorganisms are single-celled, meaning they have only one cell. But some single-celled protists are big enough to see without a microscope, and some tiny multicellular creatures are also considered microscopic.

Microorganisms live almost everywhere on Earth where there is liquid water. This includes hot springs deep in the ocean and even inside rocks within the Earth's crust. Microbes that live in such extreme places are called extremophiles.

Microbes are very important for human life and health. They help us make foods and treat sewage. They also help produce fuel, enzymes, and other useful substances. Microbes are key tools in biology for research. They are also a vital part of healthy soil. Inside the human body, microorganisms make up the human microbiota, including the important gut flora. Some microbes, called pathogens, cause many infectious diseases. This is why hygiene (like washing hands) is so important.

Understanding Microorganisms

Microorganisms can be found almost anywhere on Earth. Bacteria and archaea are nearly always microscopic. Many eukaryotes are also microscopic, such as most protists, some fungi, and even some tiny animals and plants. Viruses are usually not considered living things, but they are still studied in microbiology in a field called virology.

Free-Living Microbes

Free-living microbes get their energy in many ways. Some use photosynthesis, just like plants do, to make their own food from sunlight. Others break down natural chemicals in their environment. Many feed on things that were once living, like fallen leaves and dead animals. This process causes them to break down or decay.

Some fungi and bacteria cause food to decay. Think of moldy bread or fruit, sour milk, or rotten meat – these are examples of food decaying. In nature, decayed materials mix with soil, giving plants important nutrients. Without this process, the soil would run out of nutrients. 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 favorite foods. These include bread, cheese, yogurt, beer, and wine. They feed on the sugar in grain, fruit, or milk, which gives these foods their special texture and taste.

Harmful Microbes: Germs

Some microbes, often called germs, can cause illness or disease. They are parasites that live by invading living things. Chickenpox, mumps, and measles are all caused by viruses. Some bacteria are also germs. They cause many infectious diseases like tuberculosis and tetanus. Certain bacteria can even cause tooth decay.

We can protect ourselves from some harmful microbes. This includes storing and preparing food properly, brushing our teeth, washing our hands, and avoiding close contact with sick people.

How Microbes Help Us

Microorganisms are useful in many ways. They help produce foods, treat wastewater, create biofuels, and make a wide range of chemicals and enzymes. They are also very valuable in scientific research. Microbes are vital for agriculture because they help keep soil healthy and break down organic matter. They also have uses in fish farming, like in biofloc technology.

Making Food with Microbes

Microorganisms are used in a process called fermentation to make foods like yoghurt, cheese, curd, and kefir. Fermentation gives these foods their unique flavor and smell, and it also helps stop bad organisms from growing. Microbes are used to make bread rise and to turn sugars into alcohol for wine and beer. They are essential in brewing, wine making, baking, pickling, and other food-making processes.

Cleaning Water

Wastewater treatment plants use microorganisms to clean organic matter.

Microorganisms are key to cleaning water that has been contaminated with organic material. They can breathe in dissolved substances. This breathing can happen with oxygen (aerobic), like in a slow sand filter. Or it can happen without oxygen (anaerobic digestion), where microbes called methanogens produce useful methane gas as a byproduct.

Energy Production

Microorganisms are used in fermentation to produce ethanol. They are also used in biogas reactors to create methane. Scientists are looking into using algae to produce liquid fuels and bacteria to turn different kinds of farm and city waste into useful fuels like cellulosic ethanol.

Making Chemicals and Enzymes

Microorganisms produce many commercial and industrial chemicals, enzymes, and other active molecules. Organic acids made on a large scale by microbial fermentation include acetic acid (from acetic acid bacteria like Acetobacter aceti), butyric acid (from the bacterium Clostridium butyricum), lactic acid (from Lactobacillus and other lactic acid bacterias), and citric acid (from the mold fungus Aspergillus niger).

Microorganisms also help prepare active molecules like Streptokinase (from the bacterium Streptococcus), Cyclosporin A (from the fungus Tolypocladium inflatum), and statins (from the yeast Monascus purpureus).

Microbes in Science

A laboratory fermentation vessel

Microorganisms are essential tools in biotechnology, biochemistry, genetics, and molecular biology. Yeasts like Saccharomyces cerevisiae and Schizosaccharomyces pombe are important model organisms in science. This is because they are simple eukaryotes that grow quickly in large numbers and are easy to study. They are especially valuable in genetics, genomics, and proteomics. Microorganisms can also be used to create steroids and treat skin diseases. Scientists are even thinking about using microorganisms for living fuel cells and as a way to fight pollution.

Microbes and Soil Health

Microbes can make nutrients and minerals in the soil available to plants. They also produce hormones that help plants grow, boost the plant's immune system, and can either start or stop stress responses. Generally, a wider variety of soil microbes leads to fewer plant diseases and better crop yields.

Microbes and Human Health

All animals seem to have bacteria and protozoa living in or on them without causing much harm. Sometimes, like with plant-eating animals, these microorganisms are vital for digesting 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 our gastrointestinal tract help with gut immunity. They also make vitamins like folic acid and biotin, and they break down complex carbohydrates that we can't digest on our own. Some microorganisms that are good for health are called probiotics. You can find them as dietary supplements or added to certain foods.

Images for kids

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  Antonie van Leeuwenhoek was the first person 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 were true 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 10,000 times.

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  Euglena mutabilis, a photosynthetic flagellate.

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  A group of four Deinococcus radiodurans, a radioresistant extremophile bacterium.

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

See also

In Spanish: Microorganismo para niños