The microbiome It is a great ally of our health. It plays a fundamental role in the functioning of the immune and digestive systems, among many others. However, there is still very limited knowledge about how the bacteria and other microbes that make up the microbiome are acquired and transmitted between individuals.
Now a team of researchers coordinated by Nicola Segata, from Department of Cellular, Computational and Integrative Biology-Cibio from the University of Trento and the European Institute of Oncology (Italy), has determined two fundamental aspects of how humans acquire the microbiome: first, it confirms that the first transmission of the intestinal microbiome occurs at birth and is in fact very long-lasting, the Maternal microbiome bacteria can be detected in older peoples. But it also reveals that babies lack many of the bacterial species that are common in adults, which are acquired throughout life.
But above all, the work published in “Nature”, and in which 18 research centers from all over the world have participated, raises a question: What if some diseases considered non-communicable actually were?
In their conclusions, the researchers write that “the results reinforce the hypothesis that some diseases and conditions currently considered non-communicable need to be re-evaluated, and that taking into account transmissibility and social network structure will improve the design of future research of microbiomes”.
During adulthood, explains Nicola Segata, the sources of our microbiomes are primarily the people with whom we are in close contact. “The duration of interactions (think, for example, of students or couples sharing an apartment) is roughly proportional to the number of bacteria exchanged.”
In many cases, however, the bacteria can spread even between individuals who have casual and superficial interactions.
“The transmission of the microbiome has important implications for our health,” Segata points out, “since some non-communicable diseases (such as cardiovascular diseases, diabetes or cancer) are partially linked to an altered composition of the microbiome.”
Thus, he adds, the demonstration that the human microbiome is communicable could suggest that some of these diseases, currently considered non-communicable, could, at least to some extent, be communicable. Therefore, further studies on microbiome transmission can advance the understanding of risk factors for these diseases and, in the future, explore the possibility of reducing such risk, if any, with therapies that act on the microbiome or its transferable components.
For Carmen Muñoz Almagro, director of the Microbiology Laboratory at the Sant Joan de Déu Hospital in Barcelona, the relevance of the project is that there are many studies that suggest that non-communicable diseases such as diabetes, cancer or Alzheimer’s are related to the composition of the human microbiome. “The possibility that these microorganisms can be transmitted could in the future change the classification of these diseases to communicable diseases amenable to therapy directed against the microorganisms responsible for the disease,” he tells the Science Media Center.
“To confirm these hypotheses, more studies are needed and that health and research authorities make a firm commitment to exploring and discovering the relationship of the human microbiome with health and disease,” he adds.
The study raises many questions, acknowledges the first author, the Spanish researcher Mireia Valles-Colomer. «We are at the beginning; We know a lot about the transmission of Covid, but about the microbiome we know almost nothing about how these microorganisms get into our body and without which we could not live.
Until now, account to ABC Healthtransmission during childbirth had been studied above all because in metagenomics high-resolution methods are needed to carry out this analysis.
We are born almost sterile. During the first year there is 50% mother-infant transmission. Subsequently, Valles-Colomer explains, the ability to acquire new bacteria decreases.
This is the largest and most diverse work to date on the transmission of the human microbiome.
The researchers looked at how the bacteria are passed between generations (vertical transmission) and between people who live in close contact with each other, such as partners, children or friends (horizontal transmission).
In total, they analyzed more than 9,000 stool and saliva samples from participants in 20 countries and every continent in the world.
Transmission from the mother at birth is minimal, but the more time people spend together, the more bacteria they share
The study first confirmed that the first transmission of the gut microbiome occurs at birth and is very long-lasting. In fact, “maternal microbiome bacteria can be detected in older people,” he says Valles-Colomer.
However, babies lack many of the bacterial species that are common in adults. “Many of them do not tolerate oxygen, that is, we do not find them in the environment, so it is very likely that they are acquired from other people.”
The researchers also found that the oral microbiome is transmitted in a different way than the gut microbiome. In fact, the bacteria present in saliva are transmitted more frequently, but above all horizontally. Transmission from the mother at birth is minimal, but the more time people spend together, the more bacteria they share.
Valles-Colomer, who tracked the transmission of more than 800 species of bacteriastates that the study “has found evidence of a broad exchange of the gut and oral microbiome linked to the type of relationship and lifestyle.”
The results, he says, suggest that social interactions actually shape the composition of our microbiomes.
The study first confirmed that the first transmission of the gut microbiome occurs at birth and is very long-lasting
“We have also found that certain bacteria, especially those that survive best outside of our bodies, are transmitted much more frequently than others. Some of these are microbes that we know very little about, they don’t even have names.”
The report also shows that the bacteria can be acquired over a lifetime. In our study, Valles-Colomer comments, “we had a group of elderly people, between 60 and 85 years old, with their mothers still alive and we saw that the transmission of bacteria also persisted.
When analyzing 9,000 samples from different countriesnot only in Europe and the United States, the work confirms that people and communities in non-Westernized countries have a different microbiome, generally healthier and more diverse.
He has also seen that bacteria found in fossil stool samples, also present in non-Westernized populations, have disappeared from the microbiome of people in Westernized countries.
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