After five years of studying and mapping the diaper contents of over 600 healthy Danish one-year-olds, University of Copenhagen researchers found the infant gut virome to be diverse and largely temperate.
The researchers found and mapped a total of 10,000 viral species in the children's feces—a number ten times larger than the number of bacterial species in the same children. These viral species are distributed across 248 different viral families, of which only 16 were previously known.
"We found an exceptional number of unknown viruses in the feces of these babies. Not just thousands of new virus species—but to our surprise, the viruses represented more than 200 families of yet to be described viruses. This means that, from early on in life, healthy children are tumbling about with an extreme diversity of gut viruses, which probably have a major impact on whether they develop various diseases later on in life," explains Dennis Sandris Nielsen, senior author of the paper published in Nature Microbiology.
"This is the first time that such a systematic an overview of gut viral diversity has been compiled. It provides an entirely new basis for discovering the importance of viruses for our microbiome and immune system development. Our hypothesis is that, because the immune system has not yet learned to separate the wheat from the chaff at the age of one, an extraordinarily high species richness of gut viruses emerges, and is likely needed to protect against chronic diseases like asthma and diabetes later on in life," adds Shiraz Shah, first author of the paper.
Ninety percent of the viruses found by the researchers were bacteriophages. "We work from the assumption that bacteriophages are largely responsible for shaping bacterial communities and their function in our intestinal system. Some bacteriophages can provide their host bacterium with properties that make it more competitive by integrating its own genome into the genome of the bacterium. When this occurs, a bacteriophage can then increase a bacterium's ability to absorb e.g., various carbohydrates, thereby allowing the bacterium to metabolize more things," notes Nielsen. "It also seems like bacteriophages help keep the gut microbiome balanced by keeping individual bacterial populations in check, which ensures that there are not too many of a single bacterial species in the ecosystem. It's a bit like lion and gazelle populations on the savannah."