Plant microbiomes are assembled and modified through a complex milieu of biotic and abiotic factors. Despite dynamic and fluctuating contributing variables, specific host metabolites are consistently identified as important mediators of microbial interactions. We combine information from a large-scale metatranscriptomic dataset from natural poplar trees and experimental genetic manipulation assays in seedlings of the model plant Arabidopsis thaliana to converge on a conserved role for transport of the plant metabolite myo -inositol in mediating host-microbe interactions. While microbial catabolism of this compound has been linked to increased host colonization, we identify bacterial phenotypes that occur in both catabolism-dependent and -independent manners, suggesting that myo -inositol may additionally serve as a eukaryotic-derived signaling molecule to modulate microbial activities. Our data suggest host control of this compound and resulting microbial behavior are important mechanisms at play surrounding the host metabolite myo -inositol. • Host myo -inositol transport influences colonization of diverse bacterial taxa • Proteobacteria that catabolize myo -inositol exhibit higher root colonization • Diverse microbial phenotypes are altered by the presence of myo -inositol • This host compound may act as a signaling molecule to plant colonizing microbes Across the tree of life, microbiome assembly is governed by a complex molecular dialogue between hosts and their prospective microbial partners. O'Banion et al. add to the current knowledge of these exchanges by highlighting a unique role for host transport and compartmentalization of myo -inositol in mediating diverse plant-microbe interactions. [ABSTRACT FROM AUTHOR]