These colonies of microorganisms that inhabit our body perform a number of important functions for our health.
These small living beings, mostly bacteria, act in symbiosis with us, since they obtain benefits by living inside us, but they also report us various positive characteristics that the human being as a species could never carry out by itself.
- You may be interested: “The 3 types of microbiota in the human body”
Therefore, it is essential to maintain a healthy and balanced microbiota, as it protects us much more than we can imagine at first. In today’s article, we show you the three most important functions of the microbiome.
The Three Functions of the Microbiome: An Ancestral Symbiosis
First of all, before immersing ourselves fully in the world of symbiotic microorganisms with the human being, it is necessary that we clarify some essential terms.
The normal microbiota or microbiome, as we have already advanced, is a term that refers to the set of microorganisms that are normally found in different places of the bodies of multicellular beings (which includes humans). These bacterial strains are associated in colonies, usually aggregated according to their requirements and functionalities.
It is essential to be clear that any surface in contact with the outside has a characteristic microbiome. This includes the upper respiratory tract, the mouth, the sexual organs, the eyes, the skin, and of course, the gastrointestinal tract. In closed systems we do not find bacterial colonies. For example, if a presence of microorganisms is observed in the blood or in the heart, it is time to worry.
The microbiome can be defined according to various criteria beyond its location in the human physical space. Some of them are the following:
- Autochthonous microbiota : refers to those colonizing microorganisms that coexist in humans for a long time.
- Allochthonous microbiota : bacteria that are passing through, as they can survive in other environments without the need to intertwine with humans.
In addition, depending on its permanence over time, the microbiome is divided into two other different terms:
- Latent microbiota : the bacterial colonies that coexist with the human being for almost all his life.
- Transient microbiota : those microorganisms that constantly fluctuate in time.
As we might suspect, those truly symbiotic microorganisms will be those belonging to the autochthonous and latent microbiota. Needing us for their survival, they have evolved to bring us various benefits. After all, to a bacterium that lives in our body, the last thing that interests them is that we die, right?
With these terms cleared up, it’s time to dive into the three most important functions of the microbiome.
1. Food digestion
The “intestinal flora” is a term that has been used erroneously in the media over time, since these bacterial colonies have nothing to do with the world of vegetables.
The correct thing is to refer to these symbiotic microorganisms of the digestive tract as “intestinal microbiome”tag. Such is the bacterial representation in this system, that it is estimated that it can comprise one to two kilos of the total weight of the individual that presents it. There are about 1,500 species that comprise the gastric microbiota, yet only about 160 of them occur simultaneously in any given person. The composition is influenced by diet, age, environmental changes and genetic inheritance.
This indicates a high plasticity, but we can affirm that 92% of the bacteria inhabiting our gastrointestinal tract are of the genus Firmicutes and Bacteroidetes.
Intestinal microorganisms play an essential role in obtaining nutrients in humans, for example, some of them have enzymes to degrade complex carbohydrates such as cellulose, hemicellulose and pectin. These compounds follow a process that ends with the production of short-chain fatty acids, which can be assimilated by human cells. As surprising as it sounds, this may correspond to 10% of the daily calories needed in the human diet.
In addition, other bacterial strains participate in the synthesis of vitamins such as B12, B6, B1, B3 and folic acid , all of which are essential for health.
2. Activation of the immune system
We have not yet abandoned the intestinal microbiome, as it has been widely studied that it favors the specificity and efficacy of the immune system. The bacteria in contact with the lymphoid tissue associated with the mucosa of the intestine are responsible for showing the lymphocytes which strains are harmful and which are beneficial, because, after all, they are among the first microorganisms to colonize our body.
The intestinal microbiota and the gastric mucosa are responsible for maintaining a homeostatic balance in our body. This essential symbiosis is evidenced when a dysbiosis occurs (an imbalance in the bacterial colonies in this area), as various pathologies are triggered.
Some of them are Crohn’s disease and ulcerative colitis. This dysbiosis also promotes inflammatory responses modulated by the immune system, which can increase the risk of severe diseases such as cancer .
We are not moving in merely speculative terrain, since, for example, several studies have observed that when the density of Firmicutes and Bacteroidetes species in the intestinal tract decreases, the presence of pathogenic microorganisms of the Proteobacteria and Actinobacteria genera increases.
3. Competition
This last of the three functions of the microbiome allows us to leave the gastrointestinal tract, as it can be seen (as well as in many other places) clearly in the vaginal microbiome.
These bacterial colonies presumably prevent the occurrence of various urogenital tract infections, such as bacterial vaginosis, pathogenic yeast invasion, and various sexually transmitted infections (STIs).
This is due, in large part, to bacteria of the genus Lactobacillus. These microorganisms are responsible for maintaining a low pH by producing lactic acid, which inhibits the growth and proliferation of various pathogens. Beyond this, they have also been observed to produce various bactericidal and bacteriostatic compounds, which inhibit the adherence of these harmful microorganisms to the host epithelium.
Beyond this, it has been shown that bacteria of the Lactobacillus genus have a bactericidal effect towards Helicobacter pylori, since they inhibit its adherence to the intestinal epithelium and also inhibit its urease activity, essential for the survival of the second species. This is of noteworthy importance if we take into account that H. pylori has been positively correlated with the presence of colon cancer.
Another method of expelling or preventing the entry of pathogens is simple: direct competition. When a bacterial colony is already established in a given microenvironment, it consumes a not insignificant amount of nutrients if we take into account that we move in microscopic environments. Naturally,this prevents the proliferation of other microorganisms that should not be there in the first place .
Conclusions
As we have seen, the three functions of the microbiome on the human body range from the synthesis and assimilation of carbohydrates, through the specialization of the immune system and ending with direct competition with pathogenic microorganisms. These are not the only functions, but they are the most obvious.
Even so, more and more properties and synergies are being discovered between the microbiome and the human being itselftag. They are microorganisms that have a close evolutionary history with us, and therefore have evolved alongside us to maximize the benefit of a relationship that is already considered ancestral. For all these reasons, there is more and more talk of probiotics, prebiotics and faecal transplants, among other things: the search for a healthy microbiome (especially the intestinal one) responds to an increase in human survival.
Bibliographic references
- García, A., Henríquez, P., Retamal, C., Pineda, S., Delgado Sen, C., & González, C. (2009). Probiotic properties of Lactobacillus spp isolated from gastric biopsies from patients with and without Helicobacter pylori infection. Medical journal of Chile, 137(3), 369-376.
- Heintz-Buschart, A., & Wilmes, P. (2018). Human gut microbiome: function matters. Trends in microbiology, 26(7), 563-574.
- Kau, A. L., Ahern, P. P., Griffin, N. W., Goodman, A. L., & Gordon, J. I. (2011). Human nutrition, the gut microbiome and the immune system. Nature, 474(7351), 327-336.
- Ravel, J., Gajer, P., Abdo, Z., Schneider, G. M., Koenig, S. S., McCulle, S. L., … & Brotman, R. M. (2011). Vaginal microbiome of reproductive-age women. Proceedings of the National Academy of Sciences, 108(Supplement 1), 4680-4687.
- Shi, N., Li, N., Duan, X., & Niu, H. (2017). Interaction between the gut microbiome and mucosal immune system. Military Medical Research, 4(1), 1-7.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.