Melissa Manus

MELISSA MANUS, then a graduate student at Northwestern University, Evanston, Illinois, was awarded a grant in April 2021 to aid research on “The Influence of the Social Environment on the Infant Skin Microbiome,” supervised by Dr. Katherine R. Amato. Human infancy is a highly social period during which mothers rely on assistance from nonmaternal caregivers, or alloparents. Care from alloparents (i.e. allocare) often involves direct physical contact, which likely promotes the transfer of bacteria from alloparents to infants. This project investigated associations between allocare and the infant skin microbiome (the collection of bacteria living on the skin), with an emphasis on bacterial similarities between infants and their caregivers that may indicate pathways of bacterial sharing. We combined skin swab samples (to characterize the microbiome of different body sites) with questionnaire data about infant-alloparent interactions. We found that associations between allocare and bacterial diversity varied across the different infant skin sites, as well as by type of caregiving behavior. We also found that the skin microbiome of infants who received allocare was more distinct from the skin microbiome of their mothers (compared to infants who did not receive allocare), though this varied across the different skin sites. This study provides initial evidence that caregiving practices can contribute to the development of the infant skin microbiome, and highlights how microbiome science can be leveraged as a tool for exploring how the social environment impacts the biology of human infancy.