BEAMS ABSTRACT: Project 2 Diminished early life environmental microbial exposures and perturbations to the infant gut microbiome are related to asthma outcomes in childhood. Mexican populations resident in Nogales, Mexico exhibit a four-fold decrease in childhood asthma rates compared with a population of comparable ancestry resident seventy miles away across the border in Tucson, Arizona. Our preliminary data has demonstrated that these cross-border populations experience significantly distinct microbial exposures in their environment (house dust and drinking water) and that the stool microbiota of 1-month old infants raised in these environments are differentially enriched for immunomodulatory bacterial genera. This suggests that microbial differentials in environmental and personal microbiomes relate to the cross-border disparity in asthma rates observed in this population. BEAMS proposes to comprehensively examine a population of Mexican mother-infant dyads resident in Nogales, Mexico or Tucson, Arizona and their environment in early life to determine how differences in environmental, maternal and infant microbial composition and function relate to asthma disparities in this cross-border population. Project 2 will examine at high-resolution the functional attributes of the microbiome of a subset of paired maternal prenatal (vaginal and stool) and infant gut (longitudinally collected stool) samples collected from 200 mother-infant dyads, as well as their paired house dust and water samples using shotgun metagenomics, RNA-Seq and metabolomics. The study will examine functional differentials in inherited microbes and gut microbiome development in cross-border communities that relate to T2 wheezing at age 2 years (a robust predictor of asthma in later childhood) and immune development. These efforts aim to identify environmental, maternal and infant microbiome attributes that promote protection against asthma within Mexican populations.