The gut bacteria profile, when they appear, and how long they stay varied widely among babie

Chana Palmer and Patrick Brown collected daily stool samples from 14 healthy babies from birth, to the end of the first year.

They profiled the microbial communities present.

They also collected stool samples from many of the parents and siblings, as well as vaginal and breast-milk samples from the mothers.

They extracted genetic material that used a single gene that tells betweent housands of distinct microbial species.

Of the 4,000-plus genetic sequences found, 3 major taxonomic groups dominate.

There is no link between mode of delivery and onset of colonization.

The two cesarean section babies had lower bacterial counts than the others during the first week.

The twins' flora was similar to each other until one year old, when all the babies' profiles converged toward a adult-like profile.

This suggests that a baby’s initial bacterial profile is comes mainly by chance microbial encounters.

The fact that some of the early stool samples matched their mother’s breast milk or vaginal sample supports this interpretation.

The tendency of bacterial profile to converge may be due to human–microbe symbiosis, and selection pressure in the gut, where certain well-adapted microbes repeatedly wins the battle over the opportunistic early colonizers.

http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0050191