Viruses flourish in guts of healthy babies

http://www.eurekalert.org/pub_releases/2015-09/wuso-vfi091415.php

Public Release: 14-Sep-2015
Viruses flourish in guts of healthy babies
Washington University School of Medicine

Bacteria aren't the only nonhuman invaders to colonize the gut shortly after a baby's birth. Viruses also set up house there, according to new research at Washington University School of Medicine in St. Louis.

All together, these invisible residents are thought to play important roles in human health.

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Analyzing genomic material in the stool samples, the researchers noted that some of the viruses they identified are known to infect cells of the human host, but others actually infect the bacteria.

In fact, the researchers found that the kinds of viruses that infect bacteria, not human cells, were the most rich and diverse earliest in an infant's life and then their numbers declined. They also showed that strains of bacteria did the opposite, starting out with low numbers early and becoming more diverse as the babies grew into their toddler years.

The investigators suspect that the changes in population dynamics they observed in these viruses and bacteria are caused by a predator-prey relationship. The viruses that exclusively kill bacteria are called bacteriophage, literally "bacteria eater." The early diversity of bacteriophage means lots of predators with no prey. Since bacteriophage can't survive without their bacterial prey, the high bacteriophage numbers quickly go down. Faced with few predators, bacteria are then free to flourish and colonize the gut.

"The predator-prey dynamic is still a hypothesis at this point," Holtz said. "It probably has been best described in bacteriophage and bacteria living in oceans. But this relationship could explain the populations of viruses and bacteria we see, how they change over time and how they may stabilize as we age."

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