Antibiosis: What It Is, Characteristics And Examples
Microorganisms are the basis of existence on Earth. In 2018, a team of researchers decided to quantify the amount of biomass in the form of carbon present on our planet, and their results were published in the journal Proceedings of the National Academy of Sciences.
After their calculations, they found out that 15% of the organic matter on the Earth’s surface (70 gigatons) was locked in the least expected place: microscopic living beings specifically, bacteria.
You also don’t have to go very far to discover the abundance of these microorganisms in the environment, since it is estimated that every 6.5 square centimeters of a smartphone screen there are 25,000 bacterial units, a value 10 times greater than the microbial load it presents, for example, a dog’s food bowl.
With these data, it is clear to us that bacteria surround all habitable surfaces in the world, from our mouth and eyes to the surface with the maximum environmental inclemencies where radioactivity is the only resource (as is the case of Desulforudis audaxviator). For many bacteria to delimit their terrain and be able to specialize without competition, They carry out an interaction called “antibiosis” Today we tell you everything about her.
Before talking about antibiosis, it is necessary to highlight that there are many types of biological relationships in the world of bacteria. From a scientific point of view, A biological interaction is defined as the effect that two taxa or species have on each other when interacting in the ecosystem in which they coexist You may be familiar with the mutualism between clownfish and anemone: the tentacles of the invertebrate protect the fish and, in turn, the animal deworms the anemone and feeds on pathogens that can harm it.
In the bacterial world, phenomena such as parasitism, symbiosis, commensalism or amensalism become much more diffuse, since we are moving to microscopic scales. A clear example of parasitism is that of the Helicobacter pylori bacteria with humans: this microorganism drills into the intestinal mucosa of the carriers and secretes the enzyme urease, which promotes the conversion of chemical urea into ammonia. Prolonged exposure to this compound causes, in 20% of cases, the intestinal mucosa to be damaged and ulcers to appear.
On the other side of the coin, we find the symbiotic relationship of the bacterial flora in the environment of our gastrointestinal tract. Colonies of various genres (Firmicutes, Bacteroidetes, Actinobacteria and more) They help us degrade and metabolize plant compounds (up to 10% of the calories in our diet), activate our immune system during our early stages of life and also prevent other microorganisms from proliferating in our tissues. It is this last concept that draws our attention the most right now, since we can effectively link it to the phenomenon of antibiosis. It’s time to get into flour.
What is antibiosis?
From the broadest point of view, an antibiosis can be defined as any relationship between two organisms that is harmful to at least one of them. In the most literal meaning of the term, it means the opposite concept to symbiosis, that interaction that brings some type of benefit to those involved in it
For example, a predation relationship could be an antibiosis: one of the two specimens dies so that the other can survive another day. Following this train of thought, all types of parasitism would be antibiosis in themselves.
In any case, the true interest of this word lies in its microbiological meaning: in the world of bacteria and other microscopic organisms, We can define antibiosis as a relationship between two bacteria, in which one actively expels the other through the secretion of a specific metabolic compound, called an antibiotic Before continuing, it is necessary to mention the most important antibiosis phenomenon for humanity: that of Penicillum versus other microorganisms.
Penicillium and antibiotics
When we talk about penicillin, we are referring to a group of beta-lactam antibiotics produced by various species of ascomycete fungi of the genus Penicillium. Of the more than 300 species included in this taxon, the most famous is Penicillium chrysogenumdiscovered by Alexander Fleming in 1928.
Although the mechanisms of action of penicillin are not fully understood, It is believed that this compound acts by inhibiting the transpeptidation process, essential for the production of peptidoglycan or murein Peptidoglycan is a protective layer that is responsible for protecting bacteria from osmotic breakdown in aquatic environments, so without it, it is easier for osmotic lysis of pathogens to occur during cell multiplication.
The antibiotic properties of penicillin have already been described a thousand and one times, but why does this fungus synthesize a compound of human use? Actually, This beta-lactam antibiotic is useful for humans because we can take advantage of it, but its primary function is not to prevent us from diseases The Penicillium fungus synthesizes this compound to destroy adjacent bacteria and, therefore, have more space to grow, develop and reproduce.
When a living being is able to displace the rest of the members of the ecosystem, its ecological niche expands. If it has more access to food and space, it will be able to reproduce more and, therefore, it will have more offspring that synthesize bactericidal substances and will be able to continue growing throughout the generations. Human beings have taken advantage of this quality, but clearly the evolutionary mechanisms of living beings are not aimed at benefiting us
Antibiosis in the human body
At this point, it is essential to highlight that andThe antibiotic is the chemical that destroys the bacteria, while antibiosis is the phenomenon that leads to its production Therefore, it is not entirely correct to designate taking an antibiotic as a phenomenon of antibiosis: in this case, a natural interaction between two living beings is not taking place.
If we want to look for examples of natural antibiotics, we can focus our attention on the female reproductive system (and almost any part of the human body). For example, the vaginal flora is dominated by the microbial species Lactobacillus crispatus, L. jensenii, and L. gasseri. These protect the female reproductive tract in the following way:
Bacteria of the genus Lactobacillus ferment the glucose secreted by the cells of the vaginal mucosa and convert it into lactic acid, which acidifies the pH of the environment of the female genital tract. At a pH of 4, almost no microorganisms can grow properly, so Lactobacillus can multiply at will as long as the human host’s immune system allows it.
In addition, these bacteria also produce hydrogen peroxide (H202) during their metabolism, which prevents the establishment of many pathogens that cause sexually transmitted infections (STIs). Lactobacillus benefit from not sharing space with other microorganisms and, due to the antibiosis relationship they establish with pathogens in the environment, they protect the woman who hosts them in her genital tract.
Summary
As you may have observed, Antibiosis is the result of coevolution between species, since some actively expel others in order to obtain more resources and space to develop Human beings have learned to benefit from antibiotics, but of course, these mechanisms have never been directed towards us: the only interest of the bacteria is to reproduce and multiply, whether this is good or bad for the organism in which it lives.
Therefore, if the host’s immune system is depressed or presents some serious structural imbalance, what was initially symbiosis based on an antibiotic mechanism can become fatal parasitism. There are cases of heart infections (endocarditis) due to the lactobacilli described above, especially in patients with structural heart disease and anatomical deformities. If the bacteria has room to grow beyond its limits and immune barriers, it will surely do so, no matter what the cost.
