Listeria monocytogenes is facultative intracellular food-borne pathogen that provides an extremely amenable model for basic studies on host-pathogen interactions. This proposal is based on the results of a genetic screen that revealed a critical role of bacterial redox sensing for the upregulation of virulence gene expression in vivo. We found that L. monocytogenes glutathione synthase was upregulated during infection and determined that glutathione is the allosteric activator of the major virulence transcription factor PrfA. Based on these findings, and after decades of investigation by multiple groups, we successfully recapitulated intracellular virulence gene expression by simply adding reducing agents to bacteria grown in a chemically defined synthetic media. This finding led to another genetic screen to identify bacterial mutants that were either more sensitive or resistant to the growth inhibitory property of high concentrations of reducing agents. Analysis of the resistant mutants that arose from this screen led to the discovery that L. monocytogenes possess a Flavin-based Extracellular Electron Transport chain (FLEET) that can transport over 100,000 electrons/bacterium/second to flavin moieties present on two extracellular lipoproteins, PplA and FrdA, which can transfer electrons to ferric iron and fumarate via activation of FrdA, which encodes a fumarate reductase. We show that FLEET can mediated anaerobic growth using either ferric iron or fumarate as electron acceptors. Mutants that were more sensitive to reducing agents clustered in perR, a redox-sensing transcription factor that controls the transcriptional response to oxidative stress. We hypothesize that the oxidative stress is being generated by FLEET that we show is producing superoxide in the presence of oxygen. FLEET orthologues were found in 100s of Firmicute species including pathogens and members of the microbiota and we propose that it represents a versatile electron transfer hub present in diverse Gram-positive bacteria, that provides a selective advantage to bacteria growing anaerobically in the intestine. We also propose that FLEET activity has other consequences aerobically that may have profound effects on the cell biology of infection, virulence, and immunity.

Public Health Relevance

Diseases caused by intracellular pathogens remain one of the largest challenges facing the international biomedical community. The proposed studies on the facultative intracellular human pathogen Listeria monocytogenes will provide insight into how pathogens recognize and respond to different host cell compartments. These studies are relevant to the treatment and prevention of diseases caused by intracellular pathogens.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Bacterial Pathogenesis Study Section (BACP)
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Baqar, Shahida
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University of California Berkeley
Schools of Arts and Sciences
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Cheng, Mandy I; Chen, Chen; Engström, Patrik et al. (2018) Actin-based motility allows Listeria monocytogenes to avoid autophagy in the macrophage cytosol. Cell Microbiol 20:e12854
Mitchell, Gabriel; Cheng, Mandy I; Chen, Chen et al. (2018) Listeria monocytogenes triggers noncanonical autophagy upon phagocytosis, but avoids subsequent growth-restricting xenophagy. Proc Natl Acad Sci U S A 115:E210-E217
Chen, Chen; Nguyen, Brittney N; Mitchell, Gabriel et al. (2018) The Listeriolysin O PEST-like Sequence Co-opts AP-2-Mediated Endocytosis to Prevent Plasma Membrane Damage during Listeria Infection. Cell Host Microbe 23:786-795.e5
Nguyen, Brittney N; Peterson, Bret N; Portnoy, Daniel A (2018) Listeriolysin O: a phagosome-specific cytolysin revisited. Cell Microbiol :e12988
Light, Samuel H; Su, Lin; Rivera-Lugo, Rafael et al. (2018) A flavin-based extracellular electron transfer mechanism in diverse Gram-positive bacteria. Nature 562:140-144
Deng, Weiwen; Lira, Victor; Hudson, Thomas E et al. (2018) Recombinant Listeria promotes tumor rejection by CD8+ T cell-dependent remodeling of the tumor microenvironment. Proc Natl Acad Sci U S A 115:8179-8184
Whiteley, Aaron T; Ruhland, Brittany R; Edrozo, Mauna B et al. (2017) A Redox-Responsive Transcription Factor Is Critical for Pathogenesis and Aerobic Growth of Listeria monocytogenes. Infect Immun 85:
Portman, Jonathan L; Dubensky, Samuel B; Peterson, Bret N et al. (2017) Activation of the Listeria monocytogenes Virulence Program by a Reducing Environment. MBio 8:
Vance, Russell E; Eichberg, Michael J; Portnoy, Daniel A et al. (2017) Listening to each other: Infectious disease and cancer immunology. Sci Immunol 2:
Mitchell, Gabriel; Isberg, Ralph R (2017) Innate Immunity to Intracellular Pathogens: Balancing Microbial Elimination and Inflammation. Cell Host Microbe 22:166-175

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