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Infant gut a playground for viruses too, not just for bacteria finds research

Posted:  Thursday, September 24, 2015

Popular belief and research support that an infant’s gut is colonised extensively by bacteria. But as it emerges, they have company in viruses too. American researchers in their new study have found that unlike the adult gut, a dynamic ecosystem consisting of bacteria and viruses exists within the infant gut in the first 2 years of life. According to them, a predator-prey relationship exists between both the bacteria and viruses.

Published in the journal Nature Medicine, the study evaluated information from 8 healthy infants. The researchers analysed their stool samples to track how the babies’ bacterial gut microbiomes and viromes changed over the first two years of life. The earliest stool sample was collected when the infants were 1–4 days old.

To the researchers’ surprise, even the early samples showed the presence of viruses. When they analysed the genomic material in the stools, they found viruses belonging to 2 distinct classes: one which infects human cells and another which infects bacterial cells.

In the early infant life, the viruses which infected bacteria (called ‘bacteriophages’) were dominant following which their numbers dwindled. The bacteria showed an opposite pattern as they started out with low numbers but later diversified by the toddler years of the child. The researchers proposed a ‘predator-prey’ relationship to explain this change in numbers.

The other variant of virus identified, anellovirus, were the ones which are known to reflect the immune status of a person. Higher numbers of this virus are associated with weaker immunity. According to the researchers, this virus could be present during the intermediate period when infants are losing maternal immune protection and developing their own. Incredibly, the anelloviruses identified in this study were previously unknown.

These were the results from only 8 babies. Thus, it would be an uphill task to establish a baseline for the virome that inhabits an infant’s gut. In conclusion, the researchers said, “We don’t have enough data yet to know whether a baby’s virome is affected by the environment in the same way that the bacterial microbiome is — through, for example, diet, method of delivery and antibiotic use. We suspect that it is, but that hasn’t been shown. So much work is going into understanding how the microbiome affects our long-term health. We hypothesize that this important gut environment might be determined when we are infants. Our study is a first look into the dynamic processes that are going on in the gut in early life.”

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