MUCH OF THE MICROBIOME RESEARCH IN AGRICULTURE HAS BEEN FOCUSED ON SOIL AND SOIL-BASED SYSTEMS. ONE OF THE CHALLENGES OF MICROBIOME RESEARCH IS TO DEVELOP PREDICTIONS OF CROP PRODUCTIVITY FROM MICROBIOME INFORMATION AND MANIPULATION. WE PROPOSE THAT HYDROPONIC PRODUCTION SYSTEMS OFFER A CLOSED, LOW DIVERSITY, MODEL TO TEST AND PREDICT THE ENVIRONMENTAL IMPACT ON MICROBIOME DYNAMICS. IN HYDROPONICS, PLANT ROOTS ARE SUSPENDED IN A NUTRIENT SOLUTION AND ARE HOUSED IN ENCLOSED SYSTEMS WHERE THE ENVIRONMENT OF THE ROOT AND SHOOT ZONES ARE TIGHTLY CONTROLLED. IN ADDITION, IN THIS LOW-DIVERSITY SYSTEM, WE EXPECT TO INCREASE OUR ABILITY TO USE MICROBIOMES TO PREDICT THE IMPACT ON PLANT GROWTH, PLANT HEALTH, AND PATHOGEN PERSISTENCE. WE AIM TO CHARACTERIZE THE FUNCTIONALITY OF MICROORGANISMS IN HYDROPONICALLY GROWN PLANTS, AS WELL AS ON CHANGES IN MICROBIOME FUNCTIONALITY IN RELATION TO THE HYDROPONIC SYSTEM SETUP. IN THIS PROPOSAL, WE FOCUS ON LETTUCE DUE TO ITS MARKET AND FOOD SAFETY RELEVANCE. IN ADDITION, ITS SHORT PRODUCTION CYCLE ALLOWS FOR ROBUST AND REPLICABLE MANIPULATION REQUIRED FOR THE FUNCTIONAL CHARACTERIZATION OF LETTUCE MICROBIOME INTERACTIONS. WE MANIPULATE SPECIFIC ABIOTIC AND BIOTIC VARIABLES TO OPTIMIZE PRODUCTION PRACTICES IN ORDER TO PROMOTE A MICROBIOME THAT ENHANCES PLANT GROWTH. FURTHERMORE, WE WILL TEST THE HYDROPONIC MICROBIOME CONTRIBUTIONS TO FOOD SAFETY AND PLANT DISEASES. AT THE END OF THIS PROJECT, WE WILL DEVELOP A WORKING KNOWLEDGE ON PRODUCTION PARAMETERS THAT COULD BE USED TO PREDICT THE FUNCTIONAL DIVERSITY OF HYDROPONIC LETTUCE MICROBIOMES AND THE MAJOR MICROBIOME CONTRIBUTIONS TO PLANT PRODUCTIVITY AND HUMAN SAFETY.