226T Poster - Population Genetics
Thursday June 09, 8:30 PM - 9:15 PM

Authors:
Daisy Chen ^1,2; Nandita Garud ¹

Affiliations:
1) University of California, Los Angeles; 2) University of California, San Diego

Keywords:
Natural selection

The human gut microbiome is comprised of a complex ecosystem of microbes that reside inside of us and play an important role in our health. While the ecological dynamics of the microbiome have been intensely studied, we currently know very little about the tempo and mode of evolution of gut microbiota and how these dynamics might change over a person’s lifetime. We recently quantified the evolutionary dynamics of ~40 prevalent species of gut bacteria from infancy through adulthood. We find evidence for almost 100-fold increase in the rate of evolution and strain turnover in the infant gut compared to healthy adults, with the mother-infant transition at delivery being a particularly dynamic period in which gene loss dominates. Within a few months after birth, these dynamics stabilize, and gene gains become increasingly frequent as the microbiome matures. We furthermore find that evolutionary changes in infants show signatures of being seeded by a mixture of de novo mutations and transmissions of pre-evolved lineages from the broader family. Several of these evolutionary changes occur in parallel in multiple infants, highlighting candidate genes that may play important roles in the development of the infant gut microbiome. Our results point to a picture of a volatile infant gut microbiome characterized by rapid evolutionary and ecological change in the early days of life.