An international team of researchers conducted a five-year study of 647 Danish babies to learn more about the viral makeup of the human gut. Astonishingly, nappy samples contained approximately 10,000 species of virus, which is ten times the number of bacterial species found in the same children. Most of the viruses had never been described before, and around 90 percent of the viruses found in the nappies of the Danish babies were bacteriophages. Bacteriophages exclusively infect bacteria and make up a large part of the human microbiome.
Atlas of Infant Gut DNA Virus Diversity
The researchers found that every person has their own unique set of bacteriophages and other viruses in their gut, with almost no overlap between two different people. Each gut virome is unique but is stable over time in adults. However, right after a baby is born, this virome is very different from that of an adult, and it only stabilizes after a couple of years. To better describe this new viral diversity, the researchers created an “atlas of infant gut DNA virus diversity.” They grouped the viruses into new virus families and orders based on how similar the genomes were to each other. They found 248 families of which only 16 were previously known. The remaining 232 newly identified virus families were named after children who took part in the study.
Importance of Bifidobacterium species
Bifidobacterium species are essential for infant health, as they help with the digestion of breastmilk. These bacteria become less abundant as we age, so it makes sense that the viruses that infect Bifidobacterium are found more in babies and less in adults. Conversely, the most abundant group of adult gut bacteriophages, members of the order Crassvirales, were not as prevalent in baby poo, meaning children acquire these bacteriophages as they age.
The Unknown Virome
With the addition of these 10,000 new virus species and the many new families, it becomes clear that there is more that we do not know about the virome than what we do know. The scientific community continues to work on it, one baby poo sample at a time.