** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** MICROBIAL FUNCTIONS IN THE RHIZOBIOME CAN PROVIDE PLANT BENEFITS, SUCH AS PLANT GROWTH PROMOTION, NUTRIENT ACQUISITION, AND ADAPTATION TO STRESSES. WE HAVE CURATED A COLLECTION OF BACTERIAL ISOLATES IDENTIFIED AS CRITICAL RHIZOBIOME MEMBERS WITH HIGH POTENTIAL TO BENEFIT PERENNIAL GRASSES' GROWTH AND STRESS RESPONSE. THE ISOLATES WERE IDENTIFIED BASED ON THEIR IMPROVED GROWTH RESPONSES TO HOST PLANT SIGNALS, THEIR MUTUAL COMPATIBILITY, AND THEIR BIOGEOGRAPHIC PREVALENCE. WHEN ASSEMBLED, THIS SYNTHETIC COMMUNITY IS NAMED SYNCOM13. WE EVALUATE THE HYPOTHESIS THAT SYNCOM13 MEMBERS COLLECTIVELY PROMOTE PLANT GROWTH VIA COMPLEMENTARY MECHANISMS THROUGH THREE AIMS. THIS PROPOSAL CHARACTERIZES SYNCOM13 ISOLATES FOR THEIR POTENTIAL TO PROVIDE PLANT BENEFITS AND DEVELOPS STRAIGHTFORWARD TOOLS FOR THEIR THROUGHPUT QUANTIFICATION IN THE PLANT ENVIRONMENT. WE WILL ALSO STUDYTHE BACTERIAL CONSORTIA'S ASSEMBLY, PERSISTENCE, AND METABOLITES DURING EARLY PLANT DEVELOPMENT. FINALLY, WE WILL DETERMINETHE CLIMATE RESILIENCE OF PLANT BENEFITS GIVEN SYNCOM INOCULATION UNDER WARMING AND THE TRANSFERABILITY OF SYNCOM13 TO OTHER PLANTS.