We explain what microorganisms are, when they were discovered and their classification. Also, its characteristics and examples.
What are Microorganisms?
Microorganisms or microbes are understood to living beings or biological systems so tiny, which can only be observed using a microscope. These are much simpler forms of life than plants and animals, which present individual characteristics and an elementary biological organization.
The concept of microorganisms is, however, quite general and of practical use, without the intention of establishing any type of classification or taxonomy with respect to the living beings it refers to. In fact, there are microorganisms with very different ways of life from each otherlike a virus and a bacteria.
Some microorganisms are pathogenic, that is, capable of causing diseasewhile others are entirely harmless and some others are even part of the microscopic life that lives inside the human body.
The science that studies microorganisms is microbiology.
See also: Zoology.
Discovery of microorganisms
Since ancient times, human beings have attributed their illnesses and other perceptible phenomena to the existence of invisible beings, which often imagined as fairies or evil spiritsuntil scientific development opened to their eyes the universe of objects too tiny to see with the naked eye.
So, thanks to the invention of the microscope and other optical advanceshe was able to realize that there is very simple and very small life on almost all surfaces and substances: microorganisms or microbes.
The first to do so was Antonie van Leewenhoek in the 18th centurythrough devices of his own design; at the same time as Robert Hooke was doing it and taking notes in Micrographiahis book on microbial life.
Common characteristics of microorganisms
microscopic life It can be very, very varied in its properties and characteristics.However, a life form (or object) is considered microscopic when it cannot be perceived with the naked eye, but only with the aid of specialized magnifying tools.
To be considered microorganisms These objects must be alivealthough this seems to be called into question in the case of viruses and prions, whose existence seems to operate outside of what we understand as life.
Their sizes can vary greatly: If an average virus was the size of a tennis ball, a typical bacteria would be the size of half a tennis court and a eukaryotic cell the size of a football stadium.
Types of microorganism
Microorganisms can be of the following types:
- Virus. They are the simplest and most ultramicroscopic biological systems known, barely visible under an electron microscope. Not much is known about their evolution and there is debate as to whether they are really living beings. Their reproduction consists of infecting other unicellular organisms (or cells of a multicellular organism) and inoculating them with their genetic content (RNA or DNA, never both), so that instead of reproducing itself, the cell builds new replicas of the virus.
- Bacteria and archaea. These two types of unicellular and prokaryotic living beings (which do not have a genetic nucleus) are the simplest and most abundant microscopic living beings on the planet. They reproduce by dividing their genetic material and feed on the surrounding environment, either autotrophically (chemosynthesis) or parasitically.
- Cyanophycean algae. Called cyanobacteria, they are a type of bacteria that perform oxygenic photosynthesis, much like plants. They are much larger than ordinary bacteria.
- Protists. Protists or protozoa are single-celled eukaryotic organisms, much larger in size: they can reach 1mm. They usually live in humid or aquatic environments, although many also have parasitic lives, within complex beings such as humans. They tend to be predators of other microbes or detritophages (they feed on waste).
- Fungus. In the fungi kingdom, many varieties are microscopic, like yeasts, capable of producing infectious diseases. They are also eukaryotes.
Habitat of microorganisms
The habitat of microbes It is known as microhabitat and is equivalent to the ecosystems of higher animals, but on a very small scale.
some microbes They are considered free-livingsince they are an important part of the cycles of nature, and can be found in wastewater, surfaces, in the earth, etc.
Others, however, must live in specific habitats, such as the interior of other living beings, in the case of parasites. In the intestine of human beings there lives a true bacterial fauna that collaborates with our digestion processes, for example.
Microorganism feeding
The nutrition processes of microbes are usually of two types:
- Heterotrophs. Those that absorb their nutrients from the surrounding environment, either by letting portions of dispersed nutrients pass into their interior, or by feeding on other microorganisms (or even entering them, such as viruses). This is how they obtain the energy to keep their life cycles going.
- Autotrophs. Those that are capable of taking advantage of energy sources from the environment, such as sunlight (photosynthesis) or volcanic heat (chemosynthesis) to undertake chemical processes that provide them with usable energy.
Observation of microorganisms
To observe most microbes a microscope is requiredsince the majority are between 0.4 and 5 micrometers (bacteria).
Viruses are even smaller and require powerful microscopes (between 10 and 300 nanometers), while some protozoans are so large that they almost reach a millimeter in size and can be observed with a magnifying glass.
Culture of microorganisms
Microbes can be grown in the laboratory for scientific study and use. There are two ways of growing them:
- Aerobic. This is the simplest technique, which involves using ordinary atmospheric conditions. However, only microbe species that live in an oxygen-rich environment will grow with this system.
- Anaerobic. It is the specialized technique for anaerobic microorganisms, that is, they do not require oxygen. It consists of replacing this gas with nitrogen, to reproduce the conditions in which many species grow in volcanic, underground or even intestinal contexts.
Pathogenic microorganisms
Many of the diseases known to man are caused by infection of the body by microbes of diverse natureespecially viruses and bacteria.
These microscopic beings They penetrate the body through various routes (cuts in the skin, food ingestion, breathing, absorption through the skin, etc.) and once inside they reproduce and proliferate, damaging tissues and cells in the process.
Depending on the type of microbe, can be treated with antibiotics (bacteria) or antiviral (viruses), or antifungal (fungi).
Ecological role of microorganisms
Many free-living microorganisms They play a vital role in the balance of the ecosystemsince they are responsible for the decomposition of residual organic matter and its mineralization in the soil and water, to be used again by plants and other producing species.
Besides, cyanobacteria fix environmental CO2 and release oxygenessential for animal respiration.
Examples of microorganisms
Some examples of each type of microorganism are:
- Flu virus. A typical RNA virus of the family orthomyxoviridaeis known for its variability and symptoms of infection, known as a cold.
- Bacterium Escherichia coli. Abbreviated E. coli, it is an enterobacteria common in the gastrointestinal tract of warm-blooded animals, including humans. It is anaerobic and responsible for numerous intestinal and urinary infections.
- Cyanobacteria Anabaena flosaquae. A cyanobacterium of asexual reproduction (by mitosis) of the order Nostocales, common in fresh water and capable of photosynthesis.
- Amoeba protozoan. Also known as amoeba, it is a very varied cellular protist, with some species of enormous size (700/800 micrometers) and which can be free-living (as a predator) or parasitic.
- Yeast Saccharomyces cerevisiae. The best known and typical of microscopic yeasts.