Discovering Thousands of New Viruses Present in the Intestines of Babies: A Study by the University of Copenhagen

The intestine of babies, almost sterile at the start of life, gains bacteria, viruses and other microorganisms until it forms the mature intestinal microbiota around 3 years of age. Its richness and its balance depend on several factors: diet, taking antibiotics, birth methods (vaginal or cesarean). If we know rather well the bacteria that colonize the intestines during early childhood, viruses are more mysterious. Posted in Nature Medicinea new analysis of the soiled nappies of 647 Danish babies under the age of one has revealed 10,000 species of virus grouped into 248 families, the vast majority of which were previously unknown.

Hundreds of unknown virus families

These viruses pose no direct risk to the health of infants since they are bacteriophages, viruses that only attack bacteria and regulate their presence. The 10,000 new bacteriophage species have been identified by genetic sequencing. Whereas previously scientists had to isolate the virus and its host cell to describe a new viral species, the International Committee on Taxonomy of Viruses has relaxed this rule and now the identification of a viral species can only be done with a genetic sequence.

At the origin of this work, the international group of researchers, led by the University of Copenhagen, therefore analyzed the metagenome – all the DNA present in a sample – of 647 stool samples taken from babies. . Using bioinformatics techniques, they reconstructed the virome of children. This is how the 10,021 species of bacteriophages were discovered and classified in 248 families, of which 232 were completely unknown; 7,524 of the 10,021 discoveries belong to these new families.

Better understand the “dark matter” of our entrails

This study allows us to understand the incredible diversity of the intestinal virome but also to extend our knowledge of this “dark matter” that lives in our intestines. Most of the bacteriophages identified are said to be temperate, i.e. they have a lysogenic life cycle which includes the integration of part of their genome into that of the bacteria they infect, giving it a reprieve. . Temperate phages are opposed to virulent or lytic phages which only use a lytic life cycle where the host bacterium is destroyed quickly. In adults, lytic phages make up the bulk of the gut virome. Valuable information for understanding how this community of microorganisms forms and evolves, protecting us from certain diseases and strengthening our immunity from the start of life.