The bacterial symbiont, Bombella apis, is an established mutualist of honey bee larvae. However, our recent data has uncovered that B. apis transitions from a mutualist to a pathogen at high bacterial titers. In this project, GEMS trainee Audrey Parish seeks to use phenotyping, qPCR, and RNA sequencing to characterize the larval response to receiving mutualistic and pathogenic titers of its native symbiont, B. apis, across three host genetic backgrounds. This will be the first study to investigate honey bee larval gene expression across the mutualism-to-pathogenesis spectrum of a native symbiont, contributing to a better understanding of the developmental consequences of microbiome dysbiosis. Further, as RNA sequencing data often generates more novel hypotheses than can be addressed by a single project, these data promise to open new avenues for future GEMS projects investigating the honey bee larval microbiome.