** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** MANAGED BUMBLE BEES (BOMBUS IMPATIENS) AND VARIOUS SPECIES OF WILD BUMBLE BEES ARE VITAL POLLINATORS IN U.S. AGRICULTURE. HOWEVER, DISEASE THREATENS THE SUSTAINABILITY OF THEIR POLLINATION SERVICES. MOREOVER, EFFORTS TO OPTIMIZE THE HEALTH AND POLLINATION PERFORMANCE OF COMMERCIALLY PRODUCED B. IMPATIENS COLONIES ARE STILL IN THEIR INFANCY. RECENT RESEARCH SHOWS THAT BACTERIAL PROBIOTICS ARE A HIGHLY PROMISING TOOL FOR BOLSTERING DISEASE RESISTANCE AND PERFORMANCE OF HONEY BEES. HOWEVER, AS HONEY BEE BACTERIA GENERALLY FAIL TO ESTABLISH IN BUMBLE BEES, THERE IS A NEED TO IDENTIFY BUMBLE BEE-SPECIFIC BACTERIA THAT COULD BE USED TO SUPPORT THEIR HEALTH AND POLLINATION.THE OVERALL GOAL OF THIS PROJECT IS TO DEVELOP BACTERIAL PROBIOTICS SPECIFIC TO B. IMPATIENS THAT IMPROVE PERFORMANCE AND SUSTAIN POLLINATION SERVICES IN THE FACE OF DISEASE AND OTHER STRESSORS. THE SUPPORTING OBJECTIVES ARE: 1) IDENTIFY GUT BACTERIA FROM BUMBLE BEES THAT PROMOTE RESISTANCE TO CRITHIDIA BOMBI, A COMMON PARASITE IN MANAGED COLONIES THAT CAN SPREAD TO WILD BUMBLE BEES; 2) IDENTIFY GUT BACTERIA THAT IMPROVE POLLINATION-RELEVANT ASPECTS OF BUMBLE BEE PERFORMANCE (COGNITION, LIFESPAN, AND REPRODUCTION); 3) BUILD A CULTURE COLLECTION TARGETED TO PROMISING BACTERIAL SPECIES. A REWILDING APPROACH WILL BE USED TO DISCOVER BENEFICIAL PROBIOTICS. FROM CRYOPRESERVED GUT MATERIAL DERIVED FROM WILD B. IMPATIENS POPULATIONS, BACTERIAL STRAINS WILL BE ISOLATED, IDENTIFIED, AND EXPERIMENTALLY INOCULATED INTO BUMBLE BEES UNDER CONTROLLED LABORATORY CONDITIONS. STRAINS THAT PROMOTE ONE OR MORE ASPECTS OF BEE HEALTH WILL BE PRIORITIZED AS PROBIOTIC CANDIDATES FOR FURTHER DEVELOPMENT. OVERALL, THIS WORK WILL ACCOMPLISH THE FIRST KEY STEPS TOWARD NATURALLY DERIVED PROBIOTICS FOR MANAGED B. IMPATIENS THAT SUPPORT BUMBLE BEE HEALTH AND PRODUCTION OF BUMBLE BEE-POLLINATED CROPS.