Identification of a bacterial inhibitor against g-type lysozyme
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Lysozymes are antibacterial effectors of the innate immune system in animals that hydrolyze peptidoglycan. Bacteria have evolved protective mechanisms that contribute to lysozyme tolerance such as the production of lysozyme inhibitors, but only inhibitors of chicken (c-) and invertebrate (i-) type lysozyme have been identified. We here report the discovery of a novel Escherichia coli inhibitor specific for goose (g-) type lysozymes, which we designate PliG (periplasmic lysozyme inhibitor of g-type lysozyme). Although it does not inhibit c- or i-type lysozymes, PliG shares a structural sequence motif with the previously described PliI and MliC/PliC lysozyme inhibitor families, suggesting a common ancestry and mode of action. Deletion of pliG increased the sensitivity of E. coli to g-type lysozyme. The existence of inhibitors against all major types of animal lysozyme and their contribution to lysozyme tolerance suggest that lysozyme inhibitors may play a role in bacterial interactions with animal hosts.
KeywordsGoose-type lysozyme Lysozyme inhibitor Escherichia coli Lysozyme tolerance Peptidoglycan
L.V. holds a doctoral fellowship from the Flemish Institute for the Promotion of Scientific Technological Research (IWT). J.M.V.H. was supported a doctoral and L.C. a postdoctoral fellowship of the Research Foundation-Flanders (F.W.O.-Vlaanderen). We thank Griet Compernolle for conducting SPR analysis. We also acknowledge P. Orndorff (Department Microbiology, Pathology and Parasitology, North Carolina State University, College of Veterinary Medicine, Raleigh, NC, USA) and M.A. Valvano (Departments of Microbiology and Immunology, University of Western Ontario, London, ON N6A5C1, Canada) for providing the bacterial strains Bordetella avium 197N and E. coli GL113 ΔtolA::Km, respectively. A construct for production of recombinant T7 lysozyme was kindly donated by Prof. Dr. Smita Patel (Departement of Biochemistry, Robert Wood Johnson Medical School University of Medicine and Dentisitry, NJ, USA).
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