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Bacteriocin sensitivity in Pseudomonas syringae depends on growth stage and nutritional status

Prem Kandel: Department of Plant Pathology and Environmental Microbiology, Penn State University

<div><em>Pseudomonas syringae </em>is a plant pathogenic bacterium that causes worldwide diseases and substantial losses in crops of economic importance. Strains of <em>P. syringae</em> can produce a variety of bacteriocins, narrow-spectrum proteinaceous toxins that kill strains closely related to the producer. Bacteriocins could be used as eco-friendly antibiotic alternatives that target specific bacterial pathogens. However, as with antibiotics, we anticipate repeated bacteriocin exposure would select for genetic resistance. In selecting for resistant mutants, we observed that a fraction of cells survived bacteriocin treatment in a nonheritable manner consistent with physiological tolerance. Therefore, our objective was to determine conditions that promote bacteriocin tolerance and to investigate the underlying mechanism of this trait. Purified bacteriocin particles were applied to target cells growing under various growth stages (log vs stationary), nutrients (rich vs poor), and temperatures. Cells in low nutrients and stationary phase were found to have increased tolerance. Characterization of the tolerant cells is underway. These results will provide valuable insights in developing bacteriocins as biocontrol agents and suggest optimum conditions for their application to achieve disease management.</div>