13 May 2015 - ScienceDaily - The infant gut microbiome: New studies on its origins and how it's knocked out of balance

This new study, led by Bäckhed and Jovanna Dahlgren at the University of Gothenburg, Sweden, and Wang Jun at the Beijing Genomics Institute-Shenzhen, China, supports previous observations that most early bacterial colonizers of the gut are derived from the mother. The investigators noted that while C-section babies receive less of their mother's microbes, they are still able to be passed on through the skin and mouth.

Once bacteria take hold in an infant's gut, their populations shift depending on what a child eats. The researchers believe that the cessation of breast-feeding is such a significant moment in microbiome development because certain types of bacteria thrive on the nutrients breast milk provides. Once these nutrients are no longer available, other bacteria emerge that are more commonly seen in adults.

"Our results underscore the role of breast-feeding in the shaping and succession of gut microbial communities during the first year of life," the authors write. "The gut microbiota of children no longer breast-fed was enriched in species belonging to Clostridia that are prevalent in adults, such as Roseburia, Clostrium, and Anaerostipes. In contrast, Bifidobacterium and Lactobacillus still dominated the gut microbiota of breast-fed infants at 12 months."