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Microorganisms are organisms that, due to their small size, 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. Furthermore, they are characterized by numerous varieties, of different shapes and sizes.
Unicellular prokaryotic and eukaryotic organisms, along with certain fungi and algae, make up the universe of microbes.
Microorganisms have several characteristics in common:
- Their size is so small that they are imperceptible to the naked eye.
- Their metabolic reactions are very rapid.
- Their relationship with the environment is intense.
- They need water to metabolize.
- They develop dispersal and resistance mechanisms.
- They have the ability to alter the environment in which they are found.
- They reproduce at high speed.
- Their activity is essential for life on the planet.
- They are part of the biogeochemical cycles that occur in nature.
- They are very light, so they are transported in the air.
Within nature, different types of microorganisms can be identified. Some of them are:
Cyanophyceae algae: These are large bacteria characterized by photosynthesis very similar to plants, that is, oxygenic (they release oxygen).
Viruses: These are the most basic microbes and can only be seen with electron microscopes. They are infectious agents that, in order to replicate, must infect other unicellular organisms, into which they inoculate their genetic content (they can only reproduce in a host cell).
Fungi: Many of the organisms that make up the Fungi Kingdom are microscopic (for example, yeast).
Protists: These are large eukaryotic unicellular microbes. They typically thrive in freshwater or saltwater environments, or in very humid places. Although some varieties develop parasitic lives, these organisms generally prey on other microorganisms when feeding.
Archaea and bacteria: These are two types of prokaryotic, unicellular organisms and are the simplest microbes. They make up the most prevalent group of microbes on Earth. They feed on their habitat and reproduce through the division of their genetic material.
Cyanophycean algae
Virus
Fungi
Protists
Archaea and Bacteria
There are microorganisms that are harmful to human health because by attacking vital cells, they can cause diseases that can sometimes lead to death. Some of these microbes are:
Bacteria: These are microorganisms that belong to the Monera Kingdom, currently divided into two domains: Bacteria and Archaea. They release toxins and can survive inside or outside a cell. Furthermore, they are unicellular and lack a membrane that delimits the nucleus. Not all bacteria are pathogenic; some can be beneficial or neutral.
Viruses: These are microbes that have a spiral or spherical shape and can only reproduce within a host cell. These infectious agents have a single type of nucleic acid and are always pathogenic. Viruses can never be eliminated with antibiotics; only their symptoms can be treated.
Fungi: These microbes can cause infectious diseases and thrive on the outside of the body.
Within microorganisms, there are also varieties that are beneficial to life, the environment, and human health. Some examples where microbes play a beneficial role are:
Food Industry: Microbes play a fundamental role in the production of certain products. For example, yogurt, cheese, and beer are the result of fermented foods, thanks to the action of microbes. In these cases, microbes produce lactic acid, which helps preserve food.
Agriculture: Many of the microorganisms that inhabit the soil facilitate agricultural production, either by acting as pesticides or by aiding plant growth.
Human Body: Some microorganisms participate in certain processes within the human body (such as digestion) and even act to defend against other organisms that can affect health.
Trash: Through certain biological processes (such as stabilization or decomposition), microbes clean waste. They eventually convert the waste into humus or compost.
Some of the best-known and most studied microorganisms that can cause disease are:
Escherichia coli: These are the microbes that cause diseases such as hemorrhagic diarrhea or kidney failure. They live in the intestines.
Salmonella: These are microorganisms that cause various diseases. Many of them are diarrheal. They are spread through urine and feces.
Streptococcus pneumoniae: These are the microbes that cause diseases such as pneumonia, sinusitis, or otitis media, as well as meningitis.
Mycobacterium tuberculosis: In general, they affect the function of the liver and lungs, but they can infect any organ in the body. They are microbes that are very resistant to cold.
Yernisia 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.
Basillus cereus: It is a microorganism that causes food poisoning, vomiting, diarrhea, and nausea. It lives in food and reproduces very easily.
Treponema pallidium: This microorganism is treated with penicillin and is characterized by not surviving outside the body. This microbe also causes the sexually transmitted disease syphilis.
Escherichia Coli
Streptococcus pneumoniae
Yersinia pestis
Remember to review the answers to the open-ended questions at the bottom of this page.
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We recommend visiting the following material for greater knowledge or understanding on the topic:
1. What are microorganisms? 2. Types of microorganisms 3. What are microbes ?6. Due to their small size, they are imperceptible without the aid of a microscope.
7. In the food industry, certain microbes ferment foods such as yogurt, cheese, or beer, producing lactic acid that aids in preservation and gives products unique characteristics.
8. In agriculture, some microorganisms act as natural pesticides or promote plant growth through processes that improve soil fertility.
9. During the 19th century, electrochemistry enabled the development of techniques such as galvanization and the production of hydrogen peroxide.
10. Because it allows the development of technologies such as rechargeable batteries and fuel cells, which are key to energy storage.
References:
1. Equipo editorial, Etecé. (2025, 21 mayo). Microorganismo - Concepto, características, tipos y ejemplos. Concepto. https://concepto.de/microorganismo/ https://concepto.de/microorganismo/
2. What are microorganisms? (s. f.). University Of Bergen. https://www.uib.no/en/geobio/56846/what-are-microorganisms https://www.uib.no/en/geobio/56846/what-are-microorganisms
3. Pelczar, J, M., Pelczar, & M, R. (1999, 26 julio). Microbiology | Definition, History, & Microorganisms. Encyclopedia Britannica. https://www.britannica.com/science/microbiology/Types-of-microorganisms https://www.britannica.com/science/microbiology/Types-of-microorganisms
4. Institute for Quality and Efficiency in Health Care (IQWiG). (2022, 5 abril). In brief: What are microbes? InformedHealth.org - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK279387/ https://www.ncbi.nlm.nih.gov/books/NBK279387/
5. FuseSchool - Global Education. (2019, 29 enero). Microorganisms | Genetics | Biology | FuseSchool [Vídeo]. YouTube. https://www.youtube.com/watch?v=YSitT0oOoyc https://www.youtube.com/watch?v=YSitT0oOoyc
6. Fun World For Kids. (2021, 15 noviembre). Microorganisms - What are Microorganisms? (Learning Videos For Kids) [Vídeo]. YouTube. https://www.youtube.com/watch?v=GuwRiqETHF8 https://www.youtube.com/watch?v=GuwRiqETHF8
7. THAPRO SCIENCE. (2020, 7 abril). Classification of microorganism [Vídeo]. YouTube. https://www.youtube.com/watch?v=XfrhN9MBWgY https://www.youtube.com/watch?v=XfrhN9MBWgY