** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** PHOSPHOROUS IS ESSENTIAL FOR PLANT GROWTH AND IN MANY AGRICULTURAL SOILS PHOSPHORUS AVAILABILITY LIMITS CROP PRODUCTION. PHOSPHATE-RICH FERTILIZERS CAN TEMPORARILY OFFSETS THESE DEFICIENCIES, BUT HIGH FERTILIZER USEAGE COMES WITH BOTH ECONOMIC AND ENVIRONMENTAL COSTS; LEACHING OF EXCESS PI POLLUTES AQUATIC ECOSYSTEMS, AND ROCK PHOSPHATE RESERVES, FROM WHICH PI-FERTILIZERS ARE DERIVED, ARE BEING DEPLETED. CONSEQUENTLY, INCREASING THE EFFICIENCY OF PHOSPHATE CAPTURE BY CROPS IS IMPORTANT FOR THE ENVIRONMENT AND FOR AGRICULTURAL SUSTAINABILITY. ONE APPROACH IS TO HARNESS THE PLANTS MICROBIAL PARTNERS. MOST PLANT SPECIES, INCLUDING ALL THE MAJOR FOOD CROPS, CAN INCREASE THEIR ACCESS TO PHOSPHATE THROUGH SYMBIOTIC ASSOCIATIONS WITH ARBUSCULAR MYCORRHIZAL (AM) FUNGI. AM FUNGI GROW WITHIN AND AROUND PLANT ROOTS WHERE THEIR HYPHAE CAPTURE AND TRANSFER PHOSPHATE DIRECTLY TO ROOTS. AM FUNGI HAVE CONSERVED MICROBIAL COMMUNITIES ASSOCIATED WITH THEIR HYPHAL SURFACES AND THESE COMMUNITIES HAVE THEPOTENTIAL TO INFLUENCE FUNGAL BIOLOGY AND SUBSEQUENTLY PLANT PERFORMANCE DURING AM SYMBIOSIS. IN THIS PROJECT, WE WILL EXTEND KNOWLEDGE OF HYPHAE-ASSOCIATED MICROBIAL COMMUNITY COMPOSITION IN A RANGE OF SOIL PHOSPHORUS CONDITIONS THROUGH SEQUENCE-BASED PROFILING APPROACHES. USING HIPR-FISH, A RECENTLY DEVELOPED IMAGING APPROACH THAT HAS BEEN DEPLOYED SUCCESSFULLY IN HUMAN MICROBIOME RESEARCH, THE SPATIAL ORGANIZATION OF THE MICROBIAL COMMUNITIES ON THE HYPHAE WILL BE MAPPED. SPATIAL DATA ARE VALUABLE BECAUSE HIGHER LEVEL FUNCTIONS OF A MICROBIAL COMMUNITY MAY ARISE AS THE RESULT OF MICROBIAL INTERACTIONS. COMMUNITY COMPOSITION, GENOME SEQUENCES AND SPATIAL MAPPING DATA WILL INFORM THE ASSEMBLY OF SYNTHETIC MICROBIAL COMMUNITIES. THESE WILL BE EVALUATED FOR THEIR ABILITY TO ENHANCE PLANT PHOSPHORUS NUTRITION DURING AM SYMBIOSIS, WITH A FOCUS ON ACCESSING RESIDUAL SOIL ORGANIC PHOSPHATE POOLS. THE DATA GENERATED WILL CONTRIBUTE TO A HOLISTIC UNDERSTANDING OF AM SYMBIOSES AND GUIDE PRACTICES TO IMPROVE PHOSPHATE CAPTURE AND ULTIMATELY REDUCE HIGH FERTILIZER INPUTS IN AGRICULTURE.