**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** SALMONELLA IS A LEADING BACTERIAL CAUSE OF FOODBORNE ILLNESS IN THE UNITED STATES AND SURFACE WATER SUCH AS CREEKS, RIVERS, AND PONDS ARE A SIGNIFICANT AND PERSISTENT RESERVOIR OF THIS PATHOGEN. SALMONELLA SEROTYPES CAN EXHIBIT DIFFERENT PHENOTYPES, INCLUDING THEIR CAPACITY TO CAUSE ILLNESS AND IN THEIR SURVIVAL IN THE ENVIRONMENT. SALMONELLA SEROTYPE POPULATIONS IN SURFACE WATER ARE EXTRAORDINARILY DIVERSE AND CLINICALLY IMPORTANT SEROTYPES ARE OFTEN OUTNUMBERED IN THESE ENVIRONMENTS. THERE IS A KNOWLEDGE GAP WITH RESPECT TO SALMONELLA SEROTYPE POPULATION DYNAMICS IN SURFACE WATER, IN PARTICULAR THE INFLUENCE OF ZOONOTIC SOURCE AND HOW THE LONG-TERM SURVIVAL AND COMPETITION BETWEEN SEROTYPES IMPACTS TRANSMISSION OF CLINICALLY IMPORTANT SEROTYPES. THE OVERALL OBJECTIVE OF THE PROPOSED WORK IS TO DEFINE PATHWAYS THAT INTRODUCE SALMONELLA INTO SURFACE WATER, AND TO IDENTIFY THE GENETICS UNDERLYING SALMONELLA SURVIVAL AND PERSISTENCE IN SURFACE WATER. OUR APPROACH WILL BE TO USE HIGH RESOLUTION SEROTYPE POPULATION ANALYSIS BY CRISPR-SEROSEQ, AND MACHINE LEARNING-BASED MODELING OF ZOONOTIC AND ENVIRONMENTAL VARIABLES TO UNDERSTAND THE INTRODUCTION, MOVEMENT, AND PERSISTENCE OF SALMONELLA IN SURFACE WATER. THE EXPECTED OUTCOME OF THE PROPOSED WORK IS THAT IT WILL LEAD TO NEW STRATEGIES TO CONTROL AND MITIGATE SALMONELLA IN SURFACE WATER THAT IS USED IN CROP IRRIGATION AND ANIMAL WATER SUPPLIES, WHICH WILL FACILITATE IMPROVED FOOD SAFETY AND SECURITY.