We have more bacterial cells than human cells in our body.
The last few years have brought a large number of discoveries that have catapulted the medical and biological sciences into new areas of knowledge that previously we could not but theorize.
Thanks to advances in new techniques and methodologies, investigations are becoming faster, more efficient and with more reliable results than ever before.
One of these colossal advances in the scientific medical world has been the discovery of different roles in human health that the microorganisms that colonize our body have . The microbiota, which is what we call this diverse community of viruses, bacteria, fungi and archaea, accompanies us practically from the moment of birth until our end.
In this article we will explain exactly what the microbiota is and what functions are attributed to it today.
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What is the microbiota?
Our body is made up of approximately 30 trillion (30 million million) cells that we could consider our own , since they share our genetic code. But added to this large number of human cells, we are accompanied by a similar although slightly higher number of microorganisms, among which we can count fungi, viruses and bacteria of all kinds.
We call this companion population, which outnumbers our cells by 1.3 microorganisms per human cell, the microbiota , companions without which we could hardly survive in the same way as today.
The microbiota is distributed throughout our body, in the nasal, oral, vaginal and intestinal mucosa, as well as covering our skin. In each place the population of microorganisms that make it up varies , adapting to the characteristics of its habitat. This means that the microbiota that is present in our mouths will be markedly different from the one that we can find between our toes.
The microbiota does not only vary throughout our body, but its composition also varies between people. Some of this variation between microbiota causes, for example, the differences in body odor that exist between different people.
Currently there are many studies that try to determine the exact composition of our microbiota in addition to the functions it performs , since it is theorized that this can open the doors to a deeper understanding of certain functions of our body, as well as certain diseases and possible uses therapeutics of our microbial population.
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Functions of the microbiota
The microbiota, which you can also find referred to as the microbiome (although this term technically refers to the genetic material of the microbiota and not to the organisms that make it up), has aroused the interest of many scientists, since recent studies attribute completely unexpected functions to them Until now.
Below we list some of these functions so that we better understand the role of the microbiota.
1. Protection against invading pathogens
One of the first functions attributed to the microbiota is to defend us from other microorganisms that are less benevolent than those that accompany us in our daily lives. Although some of the fungi and bacteria that we have naturally on our skin are opportunistic pathogens (that is, they are waiting for the right conditions to attack us), most of these are commensals that will not affect our health.
One of the main benefits of maintaining a large population of microorganisms in our body is to prevent other microorganisms from easily colonizing our skin and mucous membranes . If our body is “saturated”, it is difficult for a new microorganism to arrive and spread easily throughout our body, since the pre-existing population of microorganisms will compete with the invaders for resources, stopping and avoiding infections.
A clear example of this function is found in the now popular fecal transplants . This practice consists of extracting the intestinal microbiota from a healthy donor to introduce it into the intestine of a patient with alterations in the microbiota, such as those people intestinally infected by the Clostridium difficile bacteria . Fecal transplantation is an effective treatment in approximately 85% of cases.
2. They help us in digestion
The gut microbiota is incredibly diverse and the subject of much of the microbiota research being done today. It is natural, since the role of the intestinal microbiota is essential for various functions of our body. One of the most obvious is its influence on food .
One of the clearest examples of the role of the microbiota in food is found in the breastfeeding period. Newborns consume breast milk, but some of the sugars found in it cannot be assimilated by the infant.
Luckily, your intestinal microbiota, which you will have obtained mainly through contact with your own mother, especially in the period around childbirth, will be able to partially digest these sugars, facilitating their absorption by the digestive system.
3. They provide nutrients
In addition to defending our intestine and facilitating our digestion, bacteria are essential in obtaining certain nutrients necessary for our body . Some of the microorganisms in our intestines play a fundamental role in the synthesis of vitamin B, vitamin K and the metabolism of bile acids.
4. They interact with our immune system
The fermentation of dietary fiber in our body is carried out by the bacteria in our intestine. The products resulting from this fermentation are known as SCFA (short chain fatty acids) and their influence on our body modulates the structure of our intestinal cells, the regulation of our appetite, glucose homeostasis and our tendency to to obesity, among others.
An interesting function of SCFAs is to modulate our immune system , reducing chronic inflammation processes and favoring the proliferation of regulatory T immune cells. In theory, this would help us protect ourselves from the oxidative stress typical of immune processes.
5. They influence our nervous system
The multiple metabolites resulting from the metabolic processes of our intestinal microorganisms are capable of influencing even our nervous system through multiple pathways .
The effects of the microbiota on the nervous system are still under study, with experiments carried out mainly at the level of animal models, but it seems like a promising area of study. Among its currently known effects we can count the maturation of certain glial cells or the direct and indirect interaction with the vagus nerve through hormonal factors or the influence of enterochromaffin cells of the gastrointestinal tract.
Bibliographic references
- Shogbesan, O., Poudel, DR, Victor, S., Jehangir, A., Fadahunsi, O., Shogbesan, G., & Donato, A. (2018). A Systematic Review of the Efficacy and Safety of Fecal Microbiota Transplant for Clostridium difficile Infection in Immunocompromised Patients. Canadian journal of gastroenterology & hepatology, 2018, 1394379. doi:10.1155/2018/1394379.
- Chambers, ES, Preston, T., Frost, G., & Morrison, D.J. (2018). Role of Gut Microbiota-Generated Short-Chain Fatty Acids in Metabolic and Cardiovascular Health. Current nutrition reports.
- Cani PD Human gut microbiome: hopes, threats and promises Gut 2018;67:1716-1725.
- Amon P, Sanderson (2017). What is the microbiome? Archives of Disease in Childhood – Education and Practice.
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.