THE PLANT ROOT MICROBIOME IMPACTS PLANT HEALTH THROUGH GROWTH PROMOTION AND SUPPRESSION OF INFECTIOUS DISEASE. MANY MICROBIOME INTERACTIONS ARE MEDIATED BY BACTERIAL SECONDARY METABOLITES. THIS POSTDOCTORAL RESEARCH PROJECT PROPOSAL AIMS TO BETTER UNDERSTAND THE METABOLITES THAT MEDIATE BACTERIAL INTERACTIONS IN A RHIZOSPHERE MODEL COMMUNITY. THE CENTRAL ORGANISM IN THIS MODEL SYSTEM, BACILLUS CEREUS UW85, HAS BEEN USED SUCCESSFULLY AS A BIOCONTROL AGENT FOR ALFALFA AND SOYBEAN. HOWEVER, VARIABILITY IN ITS PERFORMANCE AND PERSISTENCE REMAINS A CHALLENGE. WE HYPOTHESIZE THE VARIABLE EFFECTIVENESS OF B. CEREUS UW85 AS A BIOCONTROL AGENT IS, IN PART, DUE TO ITS INTERACTIONS WITH OTHER MICROBES IN THE RHIZOSPHERE COMMUNITY. OUR MODEL COMMUNITY, COMPRISED OF RHIZOSPHERE ISOLATES, ENABLES THE COUPLED GENETIC AND METABOLOMIC INVESTIGATION OF SECONDARY METABOLIC PATHWAYS WITHIN B. CEREUS UW85 THAT MEDIATE MULTIPARTITE COMMUNITY DYNAMICS, BOTH IN VITRO AND ON THE PLANT HOST. SECONDARY METABOLIC PATHWAYS AND THEIR RESPECTIVE METABOLITES WILL BE IDENTIFIED WITH MODERN GENOMIC TECHNIQUES AND GENETICALLY VERIFIED. TRANSCRIPTOMIC STUDIES WILL BE PERFORMED TO BETTER UNDERSTAND THE GLOBAL CHANGES IN GENE EXPRESSION IN RESPONSE TO B. CEREUS UW85 SECONDARY METABOLISM FOR COMMUNITY MEMBERS ALONE, IN PAIRWISE INTERACTIONS, AND IN TRIPARTITE INTERACTIONS. THIS PROPOSED WORK EXPANDS THE TECHNICAL EXPERTISE OF THE HANDELSMAN LAB AND THE PD AND IS ATTAINABLE WITHIN THE TRAINING PERIOD. FURTHER, IT DIRECTLY ADDRESSES THE PLANT HEALTH AND PRODUCTION PRIORITY OF THE AFRI FARM BILL. INVESTIGATIONS INTO THE SECONDARY METABOLITES AND PATHWAYS INVOLVED IN MICROBIAL INTERACTIONS MAY INFORM NOVEL SOIL MANAGEMENT TECHNIQUES OR IMPLEMENTATION OF BIOCONTROL AGENTS TO SUPPRESS PLANT DISEASE.