** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE RHIZOSPHERE MICROBIOME IS ESSENTIAL FOR OVERALL PLANT AND SOIL HEALTH. TO BETTER UNDERSTAND HOW MICROBES AFFECT THEIR ENVIRONMENTS, IT IS IMPORTANT TO UNDERSTAND THE MOLECULAR CROSSTALK MEDIATING MICROBIAL INTERACTIONS IN COMMUNITIES. WITHIN MICROBIAL COMMUNITIES, EACH MICROBE RESPONDS TO ENVIRONMENTAL CUES, SUCH AS SECONDARY METABOLITES. SECONDARY METABOLITES ARE SMALL MOLECULES PRODUCED BY BACTERIA, FUNGI, AND PLANTS THAT ARE NOT ESSENTIAL TO THEIR GROWTH. THESE SMALL MOLECULES HAVE BEEN LARGELY STUDIED FOR THEIR PESTICIDE, ANTIBIOTIC, AND OTHER MEDICINAL PROPERTIES. DESPITE THEIR UBIQUITY, LITTLE IS KNOWN ABOUT THE MECHANISMS THAT GOVERN SECONDARY METABOLITE PRODUCTION AND FUNCTION IN THE CONTEXT OF MICROBIAL COMMUNITIES IN THEIR NATURAL HABITATS SINCE THEY ARE NOT ALWAYS PRODUCED AT INHIBITORY CONCENTRATIONS. OUR GENETICALLY TRACTABLE MODEL SYSTEM THE HITCHHIKERS OF THE RHIZOSPHERE (THOR)--COMPOSED OF B. CEREUS AND ITS TWO CO-ISOLATES FROM FIELD-GROWN SOYBEANS AND ALFALFA ROOTS, PSEUDOMONAS KOREENSIS AND FLAVOBACTERIUM JOHNSONIAE--WILL ALLOW US TO DISSECT THE EFFECTS OF RHIZOSPHERE MICROBES ON PLANTS IN A COMMUNITY WITH DEMONSTRATED RELEVANCE TO THEIR NATURAL ECOSYSTEM. I AIM TO IMPROVE OUR UNDERSTANDING OF RHIZOSPHERE MICROBIAL COMMUNITIES TO ENABLE THE DEVELOPMENT OF SUSTAINABLE STRATEGIES TO ENHANCE AGRICULTURAL PRODUCTION BY REDUCING CROP LOSSES AND SUPPRESSING DISEASES. FOR THIS I WILL (1) UNDERSTAND THE CHEMICAL ENVIRONMENT OF THOR ON PLANT ROOTS; (2) DRAW FROM IMPORTANT CHEMICAL COMPOUNDS FROM OBJECTIVE 1 TO DETERMINE THE ROLE OF SECONDARY METABOLITES ON GROWTH AND PERSISTENCE OF THOR ON PLANT ROOTS; (3) EXPLORE THE IMPACT OF THOR ON DISEASE SUPPRESSION. TOGETHER THESE RESULTS WILL ALLOW US TO IDENTIFY BIOLOGICALLY RELEVANT INTERACTIONS THAT AFFECTS THE SUCCESS OF MICROBES IN PLANT AND SOIL THAT WILL BENEFIT PLANT HEALTH.