**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 HONEY BEE IS ONE OF THE MOST ECOLOGICALLY AND ECONOMICALLY IMPORTANT POLLINATORS WORLDWIDE. PERHAPS THE BIGGEST THREAT FACING BEES (BOTH IN INDUSTRY AND NATURE) IS PATHOGEN-BORNE DISEASE. TWO OF THE MOST PROMINENT BEE DISEASES, AMERICAN FOULBROOD AND VARROA MITE INFECTION, HAVE BEEN DIFFICULT TO CONTAIN, CONTRIBUTING TO OVER $300 MILLION IN HIVE REPLACEMENT COSTS PER YEAR AND DECLINING FOOD SECURITY. CURRENT THERAPEUTICS LACK SPECIFICITY, EFFICACY, AND TOLERABLE SIDE-EFFECT PROFILES. FORTUNATELY, SYNTHETIC BIOLOGY OFFERS A SOLUTION THROUGH THE USE OF SYMBIONT ENGINEERING. BEE SYMBIONTS HAVE PREVIOUSLY BEEN GENETICALLY MODIFIED TO COMBAT VARROA INFECTIONS IN INDIVIDUAL ADULT BEES. HOWEVER, LARVAL AND HIVE-LEVEL INFECTIONS REMAIN UNTAMED. FURTHER, USE OF SYMBIONTS TO COMBAT FOULBROOD HAS NOT YET BEEN ATTEMPTED. IN THIS PROPOSAL, I AIM TO ENGINEER HIVE-ASSOCIATED BACTERIA TO KILL BEE PATHOGENS. THE NATURAL HIVE-ASSOCIATED BACTERIUM BOMBELLA APIS WILL BE ENGINEERED TO EXPRESS ANTIMICROBIAL BACTERIOCINS TO TARGET THE FOULBROOD-CAUSING AGENT PAENIBACILLUS LARVAE. ADDITIONALLY, B. APIS WILL BE USED TO KILL LARVAE-ASSOCIATED VARROA MITES THROUGH SYMBIONT-MEDIATED RNAI. EFFICACY FOR BOTH THERAPEUTICS WILL BE MEASURED IN TERMS OF EFFECTIVE PATHOGEN KILLING AND IMPROVEMENT OF BEE LARVAL SURVIVAL AND HEALTH.THIS RESEARCH PROJECT AIMS TO PROVIDE NOVEL THERAPEUTICS IN THE FIGHT AGAINST TWO OF THE BIGGEST BEE PATHOGENS, LEADING TO IMPROVED EFFICIENCY OF NATURAL AND COMMERCIAL CROP POLLINATION. THIS WORK DIRECTLY ADDRESSES NIFA AFRI FARM BILL PRIORITY AREA PHPPP, PROGRAM AREA 1F. POLLINATOR HEALTH: RESEARCH AND APPLICATION (A1113) THROUGH THE DEVELOPMENT OF NEW THERAPEUTICS TO PROMOTE POLLINATOR HEALTH. FINALLY, NOTE THAT RESEARCH USING ENGINEERED ORGANISMS WILL BECARRIED OUT IN A LABORATORY (NOT OUTDOORS), ACCORDING TOSTANDARD BIOSAFETY PROCEDURE.