** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** POLLINATION IS VITAL FOR FOOD PRODUCTION, YET KEY POLLINATORS, INCLUDING BUMBLEBEES, ARE DECLINING AT ALARMING RATES. TO STOP THESE DECLINES, WE MUST FIND WAYS TO BOLSTER BUMBLEBEE HEALTH. ONE PROMISING APPROACH IS TO IMPROVE GUT MICROBIOME FUNCTIONALITY USING PROBIOTICS. THE BUMBLEBEE GUT MICROBIOME INCLUDES FIVE UBIQUITOUS CORE BACTERIAL SPECIES AND VARIABLE MIXTURES OF NONCORE SPECIES. COMPOSITION OF THESE BACTERIAL SPECIES, AND STRAINS WITHIN THEM, VARIES EXTENSIVELY AMONG BUMBLEBEES. YET HOW THIS VARIATION IMPACTS HOST FUNCTION--AND WHETHER IT CAN BE LEVERAGED TO SUPPORT BUMBLEBEE HEALTH--ARE UNKNOWN. THE PROPOSED RESEARCH AIMS TO DEVELOP NATIVE PROBIOTICS TO PROMOTE THE HEALTH AND POLLINATION SERVICES OF MANAGED BUMBLEBEES. THIS ADDRESSES THE AFRI PRIORITY AREA PLANT HEALTH AND PRODUCTION AND PLANT PRODUCTS, BY DEVELOPING A NEW APPROACH TO MAINTAIN POLLINATOR HEALTH IN THE FACE OF ENVIRONMENTAL CHANGE (PROGRAM AREA POLLINATOR HEALTH: RESEARCHAND APPLICATION; A1113). WE WILL DESIGN PROBIOTICS AND OPTIMIZE THEIR DELIVERY TO BEES, WHILE EVALUATING THE POTENTIAL IMPLICATIONS FOR CONSERVATION IF PROBIOTICS CAN BE TRANSMITTED AMONG COLONIES OR SPECIES IN THE ENVIRONMENT. TO DO SO, WE WILL USE TOOLS AND CONCEPTS FROM MICROBIAL ECOLOGY, BIODIVERSITY-ECOSYSTEM FUNCTION THEORY, AND METAGENOMICS. THIS RESEARCH WILL IMPROVE UNDERSTANDING OF HOW MICROBES SHAPE THE HEALTH OF A CRITICAL GROUP OF POLLINATORS AND PAVE THE WAY FOR ECOLOGICALLY INFORMED DESIGN OF FUTURE PROBIOTICS, IN BOTH BEES AND OTHER HOST ORGANISMS. BY FORTIFYING THE HEALTH OF KEY POLLINATORS AND LIMITING THEIR POPULATION DECLINES, THE U.S. WILL BE BETTER ABLE TO PROTECT FOOD PRODUCTION IN THE FUTURE.