Microorganism

We explain what a microorganism is, its characteristics and classification. Also, beneficial and harmful microorganisms.

What is a microorganism?

Microorganisms are those organisms that, Due to their small size, they are imperceptible to the eye.

Also called “microbes,” these organisms have a very basic biological organization: a significant proportion of them have just a single cell. In addition, they are characterized by numerous varieties, of different shapes and sizes.

Prokaryotic and eukaryotic unicellular organisms, along with certain fungi and algae, make up the universe of microbes.

See also: Microbiology

Characteristics of microorganisms

Microorganisms have a series of characteristics in common:

• Their size is so small that they are imperceptible to the naked eye.
• Their metabolic reactions are very fast.
• The relationship they maintain with the environment is intense.
• They need water to metabolize.
• They develop dispersion and resistance mechanisms.
• They have the ability to alter the environment in which they are found.
• They reproduce at great speed.
• Its activity is essential for life on the planet.
• They are part of the biogeochemical cycles that take place in nature.
• They are very light, so they are carried in the air.

Types of microorganisms

Within nature, different types of microorganisms can be identified. Some of them are:

• Virus. They are the most basic microbes and can only be perceived with electron microscopes. They are infectious agents that, to replicate, must infect other single-celled organisms, to which they inoculate their genetic content (they can only reproduce in a host cell).
• Cyanophycean algae. They are large bacteria and are characterized by photosynthesis in a very similar way to plants, that is, oxygenic (they release oxygen).
• Fungus. Many of the organisms that make up the Kingdom Fungi are microscopic (for example, yeast).
• Protists. They are large-volume eukaryotic single-celled microbes. They generally develop in freshwater or saltwater aquatic environments, or in very humid places. Although some varieties develop parasitic lives, in general, these organisms prey on other microorganisms when feeding.
• archaea and bacteria. They are two types of prokaryotic and unicellular organisms, and they are the simplest microbes. They make up the group of microbes with the greatest presence on Earth, they feed on the habitat in which they are found and their reproduction is from the division of their genetic material.

Harmful and beneficial microorganisms

Harmful Microorganisms

There are microorganisms that are harmful to people's health, because by attacking vital cells, they can cause diseases that, in some cases, can lead to death. Some of these microbes are:

• bacteria. They are microorganisms that belong to the Monera Kingdom, today divided into two domains: Bacteria and Archaea. They release toxins and can survive inside or outside a cell. In addition, they are unicellular and lack a membrane that delimits the nucleus. Not all bacteria are pathogenic, but some can be beneficial or neutral for health.
• Virus. They are microbes that have a spiral or spherical shape and can only reproduce inside a host cell. These infectious agents have a single type of nucleic acid and are always pathogenic. Viruses can never be eliminated with antibiotics and only their symptoms can be attacked.
• Fungus. These microbes can cause infectious diseases and develop on the outside of bodies.

Beneficial microorganisms

Within microorganisms there are also varieties that are beneficial for life, the environment and human health. Some examples where microbes intervene in a beneficial way are:

• food industry. Microbes play a fundamental role in the production of certain products. For example, yogurt, cheese or beer are the result of fermented foods, thanks to the actions of microbes. In these cases, the microbes produce lactic acid that facilitates the preservation of food.
• human body. There are microorganisms that participate in certain processes within the human body (such as digestion) and even act in defense of other organisms that can affect health.
• Trash. Through certain biological processes (such as stabilization or decomposition), microbes clean up waste. They end up converting the waste into humus or compost.
• Agriculture. Many of the microorganisms that inhabit the soil facilitate agricultural production, either because they act as pesticides or because they help plant growth.

Examples of microorganisms

Some of the most well-known and studied microorganisms that can cause diseases are the following:

• Escherichia coli. They are the microbes that cause diseases such as hemorrhagic diarrhea or kidney failure. They live in the intestines.
• Salmonella. They are microorganisms that cause various diseases. Many of them are diarrheal. It spreads through urine and feces.
• Streptococcus pneumoniae. They are the microbes that cause diseases such as pneumonia, sinusitis or otitis, as well as meningitis.
• Mycobacterium tuberculosis. In general, they affect the functioning of the liver and lung, but they have the capacity to make any organ in the body sick. They are microbes very resistant to cold.
• Yersinia pestis. This microbe lives in rodents, although it is transmitted through fleas. It caused the disease known as the “Black Death” in Europe, which killed more than 200 million people.
• Bacillus cereus. It is a microorganism that causes poisoning, vomiting, diarrhea and nausea. It lives in food and is characterized by reproducing very easily.
• Treponema pallidum. It is a microorganism that is fought with penicillin and is characterized by not surviving outside the body. Additionally, this microbe causes the sexually transmitted disease called syphilis.

References

• «Microorganism» in EcuRed.
• “Microorganism” in WikiPedia, the free encyclopedia.
• “Microorganisms and diseases” at the Millennium Institute Immunology and Immunotherapy.