**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** PLANTS HOST DIVERSE ENDOPHYTIC BACTERIA THAT ARE AN IMPORTANT COMPONENT OF THE PLANT MICROBIOME. CURRENTLY, ENDOPHYTIC BACTERIA REMAIN POORLY CHARACTERIZED. ON THE OTHER HAND, BECAUSE ENDOPHYTIC BACTERIA HAVE CLOSE CONTACT WITH PLANTS AND OVERLAP WITH MANY PATHOGENS IN COLONIZING THE INTERCELLULAR SPACE, IT HAS LONG BEEN SUGGESTED THAT ENDOPHYTIC BACTERIA HAVE GREAT POTENTIAL TO CONTROL PLANT PATHOGENS. OUR LONG-TERM GOAL IS TO FUNCTIONALLY CHARACTERIZE THE ENDOPHYTIC BACTERIA OF CITRUS AND TEST THEIR APPLICATION IN DISEASE MANAGEMENT. OUR CENTRAL HYPOTHESIS IS THAT ENDOPHYTIC BACTERIA PLAY IMPORTANT ROLES IN SUPPRESSING INFECTION BY PATHOGENIC MICROBES. IN OUR PREVIOUS STUDY, WE CULTURED A LARGE NUMBER OF ENDOPHYTIC BACTERIA FROM CITRUS ROOTS AND LEAVES. WE WILL TAKE ADVANTAGE OF OUR COLLECTION OF ENDOPHYTIC BACTERIA TO INVESTIGATE THEIR BENEFICIAL TRAITS AND TEST THEIR APPLICATION IN DISEASE CONTROL. THE FOLLOWING OBJECTIVES ARE PROPOSED: INVESTIGATION OF THE BENEFICIAL TRAITS OF THE ENDOPHYTIC BACTERIA, GENOME SEQUENCING OF THE ENDOPHYTIC BACTERIA, AND ENGINEERING OF SYNTHETIC ENDOPHYTIC BACTERIAL MICROBIOMES FOR DISEASE MANAGEMENT. WE WILL USE XANTHOMONAS CITRI SUBSP. CITRI (XCC) AS A MODEL PATHOGEN TO INVESTIGATE THE CONTROL EFFECT OF THE SYNTHETIC ENDOPHYTIC BACTERIAL COMMUNITY. WE WILL INVESTIGATE THE POTENTIAL MECHANISMS RESPONSIBLE FOR THE CONTROL EFFECT AGAINST XCC. SUCCESSFUL COMPLETION OF THE PROJECT WILL GENERATE USEFUL INFORMATION REGARDING THE FUNCTION OF ENDOPHYTIC BACTERIA. ENGINEERING A SYNTHETIC ROOT ENDOPHYTIC BACTERIAL MICROBIOME AND A SYNTHETIC LEAF ENDOPHYTIC BACTERIAL MICROBIOME HAS THE POTENTIAL TO PUT THE KNOWLEDGE LEARNED INTO ACTION TO BENEFIT CROP PRODUCTION.