Fierer, also a fellow at CU's Cooperative Institute for Research in Environmental Sciences, said that during vaginal births "it appears that the newborns pick up the bacteria from the mothers on the way out. But in C-sections, the bacterial communities of infants could come from the first person to handle the baby, perhaps the father."
The new study has allowed the researchers "to capture the first moments in time" of infant bacterial communities, said Costello, a former CU-Boulder postdoctoral researcher. "The challenge now is to fill in the rest of the story by tracking microbial communities in infants to toddlers to children and adults over weeks, months and years to see how they evolve and change," she said.
The PNAS study included nine women from 21 to 33 years old and 10 newborns and was undertaken at the Puerto Ayacucho Hospital in Amazonas State, Venezuela. The babies were sampled within 24 hours of birth by swabbing their mouths and skin and by taking samples from their upper throats and gastrointestinal tracts, said Costello. The research team then used a powerful gene sequencing technique to simultaneously analyze all of the bacteria.
The effort involved isolating and amplifying tiny bits of microbial DNA, then building complementary DNA strands with a high-powered sequencing machine that allowed the team to pool hundreds of samples together in single sequencing runs to identify different families and genera of bacteria, said Knight.
"While the cost of gene sequencing is dropping rapidly, new techniques are allowing us to speed up the process at the same time," said Knight. "We can now foresee a time when such genetic sequencing could be used in relatively small biomedical laboratories in developing countries."
The new PNAS study was supported by the Venezuelan Institute for Scientific Research, the Amazonic Center for Research and Control of Tropical Diseases, the National Institutes of Health, the University of Puerto Rico, the Bill and Melinda Gates Foundation and the Crohn's and Colitis Foundation of America.