**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 BACTERIUM FLAVOBACTERIUM COLUMNARE CAUSES COLUMNARIS DISEASE, THE MOST PROBLEMATIC INFECTIOUS DISEASE IN CHANNEL CATFISH AQUACULTURE. THE MECHANISMS DRIVING VIRULENCE VARIABILITY AMONG F. COLUMNARE STRAINS ARE LARGELY UNKNOWN. IN DEPTH COMPARISONS OF THE GENOMES OF MULTIPLE REPRESENTATIVE STRAINS AND IDENTIFYING VIRULENCE FACTORS IS AN IMPORTANT STEP TOWARDS TO UNDERSTANDING HOW THIS BACTERIUM CAUSES COLUMNARIS. FURTHERMORE, THIS WOULD HELP IDENTIFY GENE TARGETS FOR MAKING ATTENUATED MUTANTS AND PROTEINS THAT COULD BE USED IN VACCINES THAT COULD BE USED AGAINST THIS DISEASE.IN THIS PROJECT WE WILL:1. SEQUENCE THE GENOMES OF 50 STRAINS OF F. COLUMNARE ISOLATED FROM DIVERSE HOST SPECIES, BROAD GEOGRAPHIC REGIONS, AND DISEASED CHANNEL CATFISH IN DIFFERENT SEASONS. THEN WE WILL USE COMPUTATIONAL BIOLOGY TO PERFORM COMPARATIVE ANALYSES OF THE GENOMES, ELUCIDATE THE FUNCTIONS OF PUTATIVE GENES, IDENTIFY PROTEIN NETWORKS AND IDENTIFY THOSE INVOLVED IN PATHOGENICITY TO CHANNEL CATFISH.2. DELETE THE PUTATIVE VIRULENCE GENES IN THE BACTERIUM (KNOCK OUT MUTANTS) AND EVALUATE THEM FOR LOSS OF VIRULENCE. IF THEY ARE ATTENUATED, EVALUATE THEIR POTENTIAL AS A LIVE ATTENUATED VACCINE.3. WE WILL USE COMUTATIONAL METHODS TO IDENTIFY GENES ENCODING PROTEINS THAT ARE GOOD CANDIDATES FOR USE AS VACCINES. THEN WE WILL CLONE THESE GENES, EXPRESS THEM AND PURIFY THESE PROTIENS AND DETERMINE IF CATFISH VACCINATED BY THESE PROTEINS ARE PROTECTED FROM COLUMNARIS DISEASE.THIS STUDY WILL HELP US UNDERSTAND THE MECHANISMS THAT F. COLUMNARE USES TO CAUSE DISEASE IN CATFISH. THIS MAY LEAD TO MORE EFFECTIVE TREATEMENTS AND PREVENTATIVE MEASURES AND BETTER VACCINES THAT CAN REDUCE LOSSES IN THE CATFISH INDUCSTRY. OUR FINDINGS WILL LIKELY BE APPLICABLE TO OTHER FINFISH AQUACULTURE SYSTENS THAT ARE IMPACTED BY COLUMNARIS DISEASE.