THE BACTERIUM AEROMONAS HYDROPHILA CAUSES A SERIOUS DISEASE AND IT IS CONSIDERED ONE OF THE MOST PROBLEMATIC INFECTIOUS DISEASE IN CHANNEL CATFISH AQUACULTURE. THE MECHANISMS DRIVING VIRULENCE VARIABILITY AMONG A. HYDROPHILA STRAINS ARE LARGELY UNKNOWN. IN DEPTH COMPARISONS OF THE GENOMES OF MULTIPLE REPRESENTATIVE STRAINS FROM DIFFERENT LOCATIONS AND IDENTIFYING VIRULENCE FACTORS IS AN IMPORTANT STEP TOWARDS TO UNDERSTANDING HOW THIS BACTERIUM CAUSES PROBLEM TO CATFISH AQUACULTURE. WE HAVE IDENTIFIED THAT EPIDEMIC A. HYDROPHILA STRAINS CONSISTENTLY ENCODE THE TAD (TIGHT ADHERENCE) SYSTEM AND LESS VIRULENT STRAINS DO NOT. 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. DELETE THE 13 TAD OPERON 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.2. WE WILL DETERMINE THE VIRULENCE OF TAD GENE MUTANTS IN CHANNEL CATFISH AND EVALUATE THE ROLE OF THESE GENES AS A VACCINE CANDIDATE. ALSO WE WILL CONDUCT THE PROTEIN EXPRESSION FOR THE PROMISING MUTANTS AND EVALUATE THEIR ROLE AS A VACCINE AS WELL.THIS STUDY WILL HELP US UNDERSTAND THE MECHANISMS THAT A. HYDROPHILA USES TO CAUSE DISEASE IN CATFISH. THIS MAY LEAD TO MORE EFFECTIVE TREATMENTS AND PREVENTATIVE MEASURES AND BETTER VACCINES THAT CAN REDUCE LOSSES IN THE CATFISH INDUSTRY. OUR FINDINGS WILL LIKELY BE APPLICABLE TO OTHER FINFISH AQUACULTURE INDUSTRIES THAT ARE IMPACTED BY A. HYDROPHILA.