The compositional development of the microbiome in early life

As the infant transitions from the isolated womb of its mother to the outside word, there are suddenly countless new sources for the acquisition of microbes. By studying which microbes succeed in making their home in the infant gut and which ones are lost, we can improve our understanding of why and how this selection process takes place. Research that includes longitudinal and dense sampling has allowed for the observation of the succession of bacterial populations throughout early development, and by utilizing sequencing tools that enable analysis at the strain level, we have found distinct patterns of transmission from the mother to the infant. Although many questions remain to be answered, current findings suggest that a balance of positive and negative selection drives the formation of ecological niches, where groups of bacteria are selected to perform tasks, creating a cost-effective community in the infant gut that benefits both the microbiota and their host.