Every time we eat food, millions of microorganisms pass through our digestive tract and a small part stays with us, sometimes to help us assimilate nutrients. Knowing how many of these bacteria, fungi and yeasts colonize us and to which species they belong seems an unattainable goal, but a mega-study in which Spanish researchers participated brings us closer to the answer.
In a book published this Thursday in the magazine cell, The members of the MASTER EU consortium, together with researchers from 14 countries, have analysed all the microbial genes present in 2,533 foods from 50 countries (the so-called metagenome) and have identified 10,899 microorganisms associated with them. Comparing them to the genomes of the microbes that usually appear in our intestines, the authors have an approximate answer to the initial question: about 3% of the microbes contained in these foods appear in the intestines of adults, while in babies they represent an average of 56%, because their diversity is still very low.
“It may seem like a small percentage, but that 3% can be extremely relevant to how it works within our body,” says Nicola Segata, a computational microbiologist at the University of Trento and co-senior author of the paper. “With this database, we can begin to study on a large scale how the microbial properties of foods could affect our health.”
A reservoir of microbes
The other relevant aspect of the result is that about half of the more than 10,000 microbes found in food, classified into 1,036 bacteria and 108 fungi, belong to unknown and unculturable species, the so-called “microbial dark matter” (microbial dark matter). Information that could help the food industry and small producers produce more consistent and desirable products, as well as guide food regulators when defining which microbes should or should not be found in certain types of foods, even helping to certify their origin and quality.
It may seem like only a small percentage, but that 3% can be extremely relevant to how it functions within our body.
Nicolas Segata
— Computational microbiologist at the University of Trento and co-lead author of the article
“We can now begin to use this reference to better understand how the quality, preservation, safety and other characteristics of foods are related to the microbes they contain,” Segata says. “Food microbiologists have been studying foods and testing for food safety for over a hundred years, but we have underutilized modern DNA sequencing technologies,” adds co-senior author and microbiologist. Paul Cotter. “This is the starting point of a new wave of studies in this field in which we fully exploit the available molecular technology.”
An Amazon with charcuterie
Among the foods whose microbes have been sequenced, there are many of Spanish origin, including several Asturian cheeses and products such as cecina and chorizo from León or blood sausage. “Above all, there are a lot of dairy products and we have introduced some foods from the meat industry, with which we work”, Avelino Álvarez Ordóñez, researcher at the Department of Hygiene and Food Technology of the University of León and León. , explains to elDiario.es co-author of the study, in which other Spanish institutions such as the Institute of Agrochemistry and Food Technology (IATA-CSIC) or the Dairy Institute of Asturias (IPLA-CSIC) also participated. Overall, in these metagenome samples, there was an overrepresentation of dairy products, with 65% of these products in all samples, compared to 17% for fermented beverages and 5% for meats.
Among the foods analyzed, there are many of Spanish origin, including several Asturian cheeses and products such as cecina and chorizo from León or blood sausage.
According to Álvarez Ordóñez, the most remarkable thing is the discovery of such a high percentage of microbes of species that are still unknown or not found in food. In a way, he admits, it is as if they were searching a pantry of possible resources – with applications in biotechnology or the food industry – that are hidden in everyday foods and that have never been analyzed in detail. “In the field of food microbiology, we traditionally study microorganisms using culture techniques, but they represent only a very small fraction,” he explains. “This result has shown us a much greater diversity than expected and invites us to continue characterizing and exploring these bacteria, until we are able to cultivate them and see their function in food.”
This reservoir of bacteria present in food, like a microscopic and unexplored Amazon rainforest, can give rise to new strains that give rise to new types of cheese or new fermentation processes that can range from bread, yogurt or beer. And Álvarez Ordóñez’s team is working in parallel on a study of microbial resistance to antibiotics present in these microorganisms, a question of great importance for public health in the medium term. “The general population may have the impression that we want food to be free of microorganisms to be safe, but we know that the vast majority can be beneficial,” he comments. “There is increasing interest in fermented foods, so having access to a wider catalogue of these good microorganisms opens up many possibilities.”
“We are what we eat”
For Ignacio López-Goñi, professor of microbiology at the University of Navarra, this is a very exhaustive article, with an impressive amount of information and data. “What caught my attention the most is that almost 50% of the microorganisms found are non-culturable, that is, about which we know very little,” he explains. “And of these, 50% are unknown and specific to a food.” Although we already know that if we apply these technologies to any ecosystem we find thousands of these non-culturable microorganisms, this seems to be a good starting point for future work. “Perhaps in the future this can help us improve food control techniques, prepare new fermentation strategies and even, why not, design new probiotics that we did not know until now,” he summarizes.
Perhaps this could help us improve food control techniques, find new fermentation strategies or design new probiotics.
Ignacio Lopez-Goñi
— Professor of Microbiology at the University of Navarra
Cristian Diaz-Muñozpostdoctoral researcher at the Laboratory of Gastrointestinal Genetics, CIC bioGUNE – BRTA, believes that this work has direct consequences on such important and immediate aspects as food safety. “Not only does it confirm the popular saying that ‘we are what we eat’, but it also reaffirms the foundations on which to establish quality probiotic foods containing microorganisms with a proven ability to colonize the digestive tract and have a positive effect on intestinal health,” explains SMC. And this underlines the importance of yeasts as an essential element of the human microbiota. “Yeasts are omnipresent in our diet (beer, cheese, wine, etc.) but often ignored in studies on intestinal health and the microbiota,” he emphasizes.
Baltasar Mayo Pérez, CSIC professor-researcher at the Dairy Institute of Asturias (IPLA-CSIC), is convinced that this is the greatest scientific effort ever made. “One of the first future research actions will be aimed at carrying out selective cultures to recover these new taxa and characterize them in depth, which will include tests to estimate their practical and safe use,” he emphasizes in statements to the SMC. “Only in this way can these new microorganisms be used as ferments or complementary cultures in the fermentation of the foods from which they are isolated,” he concludes.
