FUNCTIONAL MODULATION OF ESCHERICHIA COLI O157:H7 BY THE LETTUCE PHYLLOSPHERE MICROBIOME

Our long-term goal is to mitigate foodborne pathogen risk of leafy greens by modulating the produce microbiome and/or optimizing produce processing according to the microbiome. In this project, we aim to spatially resolve and functionally dissect phyllosphere pathogen-microbiome interactions and assess the effect of known as well as newly discovered effector epiphytes on Escherichia coli O157:H7 (EcO157) viability and localization at the single-cell resolution in planta. We plan to evaluate how the interactions may alter human pathogen phenotypes relevant to their fate during produce processing and host pathogenesis. We seek to identify genomic elements that mediate the interactions on both sides of the microbiome-EcO157 interplay. We will also determine the effect of effector strains on EcO157 survival and localization on post-harvest lettuce in modified atmosphere packaging during cold storage and temperature abuse. To achieve these goals, we propose an integrative approach that leverages our recent breakthrough on highly multiplexed spatial mapping of microbial communities and combines a variety of omics, molecular, and microbiological methods. We will focus on EcO157-lettuce as a priority model system. Results from this project will provide fine-grained evidence and mechanistic understanding to fill critical knowledge gaps and pave way to improve produce safety through microbiome manipulation.Objective 1A: Assess interactions between EcO157 and known epiphyte effector strains in the lettuce phyllosphere microbiome to test the role of iron scavenging by siderophores and biosurfactants production in the interactions.Objective 1B: Characterize the impact of known ES on EcO157 in dual species in planta model.Objective 1C. Determine the role of EcO157 interactions with ES in priming for effect of sanitizer and for virulenceObjective 2: Discover new lettuce epiphytes that inhibit or improve EcO157 viability in planta for new insights into microbiome remodeling for lettuce safety.Objective 3: Identify mechanisms of functional modulation of effector strain on EcO157 through single-cell RNA Sequencing.Objective 4: Determine the potential of known effector strains as a post-harvest in-bag hurdle to EcO157 colonization of fresh-cut lettuce.