June 29, 2007  Each Human Baby Has Its Own Unique Intestinal Microbe Collection

New parents can act strangely—for example, they often have an obsessive interest in what comes out of their baby’s bottoms. Now researchers at Stanford University join them in their diaper diving to explore when and how bacteria colonize the human gut.

Adults harbor complex microbial ecosystems within their GI tracts. These bacteria help digest food and contribute to a healthy immune system. But when a baby is born, its intestine is devoid of bacterial inhabitants. Within days, however, a cavalcade of microbes set up shop, establishing a complex intestinal community whose residents soon outnumber the baby’s own cells.

The researchers found that the early months were chaotic…with established species disappearing and new ones taking their place. But by the time the babies were 12 months old, each harbored a dynamic but unique collection of intestinal fauna.  Fraternal twins in the study had the most similar bugs, which suggests that genetics may have something to do with which bacteria stick around.  Next they’ll look at how formula versus breast milk affects a baby’s intestinal ecosystem. With so many questions left to explore, the researchers will no doubt be mining diapers for some time to come.