** 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 ROOT NODULE MICROBIOME REPRESENTS AN UNTAPPED RESOURCE TO MAXIMIZE SYMBIOTIC NITROGEN FIXATION AND PLANT HEALTH IN SUSTAINABLE AGRICULTURE. WHILE NITROGEN-FIXING RHIZOBIA (THE PRIMARY INHABITANTS OF NODULES) HAVE BEEN STUDIED FOR DECADES, THE REST OF THE ROOT NODULE MICROBIOME REMAINS UNDERSTUDIED. THE PLANT MICROBIOME IS NOW WIDELY RECOGNIZED FOR ITS ROLE IN NUTRIENT ACQUISITION AND RESILIENCE TO BIOTIC AND ABIOTIC STRESSORS.MANIPULATING MICROBIOTA FROM THE ROOT NODULE COULD MAXIMIZE SYMBIOTIC NITROGEN FIXATION IN LEGUME CROPS THROUGH DIRECT INTERACTIONS WITH RHIZOBIA, OR THROUGH INDIRECT INTERACTIONS SUCH AS ENHANCING THE RESILIENCE OF THE NODULE TO STRESS. OUR OVERALL GOAL IS TO UNLOCK THE ROOT NODULE MICROBIOME AS A TOOL FOR SUSTAINABLE AGRICULTURE AND CONTRIBUTE TO THE BROADER UNDERSTANDING OF HOW PLANTS ASSEMBLE THEIR MICROBIAL COMMUNITIES. WE WILL TAKE THE FIRST STEPS TOWARD ACCOMPLISHING THIS BY ELUCIDATING RULES THAT GOVERN THE ASSEMBLY AND COLONIZATION OF THE NODULE MICROBIOME. THIS WILL INVOLVE 1) INVESTIGATING THE RELATIVE STRENGTHS OF HOST, RHIZOBIA, SOIL AND DROUGHT STRESS AS DRIVERS OF NODULE MICROBIOME COMPOSITION, 2) ESTABLISHING A CULTURE COLLECTION OF NODULE MICROBIOTA TO HELP DEVELOP IT AS A SIMPLIFIED MODEL FOR PLANT MICROBIOME ASSEMBLY, AND 3) USING SYNTHETIC COMMUNITIES TO DIRECTLY TEST SEVERAL HYPOTHESES RELATED TO HOW THE NODULE MICROBIAL COMMUNITY IS ESTABLISHED IN THE CONTEXT OF HOST-MICROBIOME INTERACTIONS, MICROBE-MICROBE INTERACTIONS WITH RHIZOBIA, AND DROUGHT STRESS. THIS PROJECT CONTRIBUTES TO UNDERSTANDING MULTIPARTITE PLANT-MICROBE INTERACTIONS, FILLS A KNOWLEDGE GAP REGARDING HOW PLANT MICROBIOMES ARE ASSEMBLED, AND IN THE LONG RUN LEADS TO REDUCED RELIANCE ON CHEMICALS IN AGRICULTURE. ?