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Molecular Mechanisms of Human Bacterial Pathogen Internalization and Survival in Fresh Produce


<p>The goals of this project are to elucidate the mechanisms underlying the surprisingly different stomatal responses to E. coli O157:H7 and S. enterica serovar Typhimurium SL1344 and to characterize the in situ transcriptomes and survival determinants of these bacteria in fresh produce, particularly lettuce and spinach.</p><p> Specific objectives include</p><p> (1) characterization of differential stomatal responses to SL1344 and O157:H7 and</p><p> (2) determine the molecular mechanisms of SL1344 and O157:H7 survival in the phyllosphere.</p>

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<p>This research utilizes both global (transcriptomics) and targeted (specific gene mutagenesis) research approaches to address fundamental questions in plant interaction with human pathogens. The experiments described under the two specific aims provide a powerful approach to dissect the mechanism of human pathogen internalization and survival in fresh produce at the molecular level. This research will also generate genome-scale data and resources to guide future research directions in the community.A novel feature of our proposed research is that it differs from conventional studies, in which whole plants/leaves are used without distinguishing different host cell types in vivo. In particular, our proposed study takes into consideration the unique contributions of epidermis (stomate)- and apoplast-based defenses to the entry, colonization, and survival of plant and human pathogenic bacteria in the plant. As such, with the proposed research we expect to discover new phenomena and mechanisms that would likely be missed by conventional studies.In addition to making new conceptual advances, the proposed research will introduce new methodologies to the study of plant interaction with pathogenic bacteria. In particular, we have developed</p><p> (i) a novel RNA-seq pipeline for determining bacterial gene expression in planta, and </p><p>(ii) a non-invasive, thermo-imaging-based protocol for identification of Salmonella mutants defective in modulating stomatal defense. We anticipate that these new methodologies may have a "transformative" impact on the discovery of new human pathogen genes involved in stomatal modulation, colonization, and survival in plants.</p>

Melotto, Maeli
University of California - Davis
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