title: Stochastic and Differential Activation of σBand PrfA inListeria monocytogenesat the Single Cell Level under Different Environmental Stress Conditions.
abstract: During host infection, the foodborne pathogenListeria monocytogenesmust sense and respond to rapidly changing environmental conditions. Two transcriptional regulators, the alternative sigma factor B (σB) and the Positive Regulatory Factor A (PrfA), are key contributors to the transcriptomic responses that enable bacterial survival in the host gastrointestinal tract and invasion of host duodenal cells. Increases in temperature and osmolarity induce activity of these proteins; such conditions may be encountered in food matrices as well as within the host gastrointestinal tract. Differences in PrfA and σBactivity between individual cells might affect the fate of a cell during host invasion, therefore, we hypothesized that PrfA and σBactivities differ among individual cells under heat and salt stress. We used fluorescent reporter fusions to determine the relative proportions of cells with active σBor PrfA following exposure to 45°C heat or 4% NaCl. Activities of both PrfA and σBwere induced stochastically, with fluorescence levels ranging from below detection to high among individual cells. The proportion of cells with active PrfA was significantly higher than the proportion with active σBunder all tested conditions; under some conditions, nearly all cells had active PrfA. Our findings further support the growing body of evidence illustrating the stochastic nature of bacterial gene expression under conditions that are relevant for host invasion via food-borne, oral infection.
authors.affiliation: Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Guldimann
authors.affiliation: Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA.
authors.forename: Veronica
authors.initials: V
authors.lastname: Guariglia-Oropeza
authors.affiliation: Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA.
authors.forename: Sophia
authors.initials: S
authors.lastname: Harrand
authors.affiliation: Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA.
authors.forename: David
authors.initials: D
authors.lastname: Kent
authors.affiliation: Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA.
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Boor
authors.affiliation: Food Safety Laboratory, Department of Food Science, Cornell University Ithaca, NY, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Wiedmann
keywords: Listeria monocytogenes; PrfA; heat stress; salt stress; sigB; single cell; stochastic gene expression