We explain what microbes or microorganisms are and the characteristics of bacteria, viruses, protozoans, fungi and yeasts.
What are microbes?
Microbes or microorganisms are the smallest forms of life known, which are also the most abundant on the entire planet Earth. It is not possible to visualize or identify them without the help of a microscope.
Many of them coexist with us without posing any threat to us, while others have learned over the millennia to lead a parasitic or pathogenic existence, that is, as infectious agents of other organisms, especially multicellular ones.
The term microbe comes from the Greek words micros (“tiny”) and bios (“life”), and was coined during the 19th century, to give a name to the invisible beings responsible for diseases.
The idea of these beings had already appeared in the philosophical and pre-scientific sphere of humanity in the 13th century. For this reason, we still tend to associate the word microbe with pathogenic microorganisms, that is, those that carry parasitic existence.
However, Its existence was only confirmed in the 17th century with the emergence of microbiology as an organized field of scientific knowledge. Thus, the vast existing microscopic fauna and flora was confirmed, whose species are not, as initially thought, directly related.
The microbes they meet literally all over the world, both on land, waters and air, and both inside and outside our own bodies. Our intestines, for example, are home to an entire microbiotic ecosystem, which coexist with us and help us digest food.
Microbes are also responsible for the decomposition of organic matter outdoors, for the fermentation of beer, for the intense flavor of certain cheeses, and even for producing certain antibiotics.
are essential to perpetuate life on the planet although from time to time some get out of control and can cause damage to other populations of living beings. But everything is part of the processes of life on our planet.
There are numerous types of microbe, as we have said, but in this case we will focus on the best known: bacteria, viruses, parasites, fungi and yeasts, which we will see separately below.
See also: Decomposer organisms
bacteria
Bacteria (and to some extent, archaebacteria or archaea) are single-celled prokaryotic organisms very few micrometers in size (between 0.5 and 5 μm). They have diverse but recognizable shapes, such as spheres (cocci), bars (bacilli), spirals (vibrios) or helices (spirilli).
It is about the most abundant organisms on the planet whole, adapted to all types of habitat in practically any type of conditions, both in free life (dedicated to photosynthesis, chemosynthesis or decomposition processes) and in parasitic life (dedicated to infecting other organisms).
The existence of bacteria is essential for the ecological balance of the world, since deal with fundamental processes of recycling organic matter and intervene in different biogeochemical cycles.
Bacteria, in addition, can cause fatal diseases such as cholera, diphtheria, leprosy, syphilis, typhus or gonorrhea, and in these cases they are combated with various antibiotic compounds.
Continue in: Bacteria
Virus
The viruses are acellular infectious agents that is, they are so simple that they do not even consist of a cell, but they need to invade foreign cells in order to reproduce.
They are so simple that from a certain point of view It is impossible to know if they are really alive. However, they have their own genetic material that they inject into the cells they invade, to force them to synthesize new viruses instead of their usual proteins.
When the invaded cell can no longer support the number of young viruses inside, it explodes. Thus, the viruses are released and infect other similar cells.
A virus is a structure so tiny and simple that it cannot be seen through ordinary microscopes (that is, they are submicroscopic beings). However, some species can reach exceptionally large sizes.
Their body consists of a DNA or RNA molecule, encapsulated in a more or less simple protein envelope, and a layer of lipids that allows them to resist while searching for their host cell.
Viruses are found in almost all ecosystems in the world and can have very different shapes and sizes, as well as very different methods of transmission. In the case of humans, viruses can transmit everything from common diseases such as the flu to incurable diseases such as AIDS or HPV.
Protozoans
Protozoa or protozoa (from the Greek protos“first”, zoon“animal”), is the name coined in 1818 by the German naturalist Georg Goldfuss (1782-1848) for what were then considered primitive animals, that is, the simplest that exist. They were then classified within the kingdom protista, or as their own kingdom apart from eukaryotic and unicellular beings.
The protozoans are a very diverse group of microscopic beings which, sometimes, can measure a few millimeters. Around 30,000 species are known.
They tend to be abundant in aqueous environments and in the soil itself, playing various roles within the food chain: heterotrophs, predators, detritivores and even mixotrophs (since some are partially autotrophic through photosynthesis).
Protozoa generally have a unicellular body with a permeable membrane and vacuoles to digest their food, as well as flagella or other means of transport. Depending on the species, they can survive difficult environmental conditions encysted to reactivate when the time is convenient.
In some cases they can lead parasitic life, causing infections of different levels of danger. That is the case of amoebas, giardias or trichomonas. Other species, such as paramecium, live in puddles of rainwater and are completely harmless to humans.
Fungi and yeast
Located in an intermediate region between plants and animals, fungi and yeasts constitute an entire kingdom of life, of which numerous species are microscopic in size.
The mushrooms have cells with chitin cell walls different from those of plants, and proliferate in humid environments, reproducing through spores, generally asexually. In many cases, its spores serve as an infectious agent and infect living beings with parasitic fungi, thus causing diseases.
Of course, microscopic fungi do not have the traditional hyphal form of mushrooms or other ordinary fungal species, but rather are unicellular, lacking flagella and mobility.
In some cases they are of great benefit to humans, such as yeasts that are used to make bread, for the fermentation of certain liquors, or to produce biochemical substances, such as the antibiotic penicillin, produced by the fungus. penicillium.
References
- “Microorganism” on Wikipedia.
- “Introduction to microbes” in e-bug.
- “What are microbes?” in Science Magazine of the Mexican Academy of Sciences.
- “Microbes, our secret tenants” in National Geographic.
- “What are microbes?” at the National Center for Biotechnology Information (USA).
- “Microbiology” in The Encyclopaedia Britannica.
