Identification of a bacterial inhibitor against g-type lysozyme
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).
- 2.Goto T, Abe Y, Kakuta Y, Takeshita K, Imoto T, Ueda T (2007) Crystal structure of Tapes japonica lysozyme with substrate analogue: structural basis of the catalytic mechanism and manifestation of its chitinase activity accompanied by quaternary structural change. J Biol Chem 282(37):27459–27467CrossRefPubMedGoogle Scholar
- 13.Deckers D, Vanlint D, Callewaert L, Aertsen A, Michiels CW (2008) Role of the lysozyme inhibitor Ivy in growth or survival of Escherichia coli and Pseudomonas aeruginosa bacteria in hen egg white and in human saliva and breast milk. Appl Environ Microbiol 74(14):4434–4439CrossRefPubMedGoogle Scholar
- 15.Callewaert L, Aertsen A, Deckers D, Vanoirbeek KGA, Vanderkelen L, Van Herreweghe JM, Masschalck B, Nakimbugwe D, Robben J, Michiels CW (2008) A new family of lysozyme inhibitors contributing to lysozyme tolerance in gram-negative bacteria. PLoS Pathogens 4(3):e1000019. doi: 10.1371/journal.ppat.1000019 CrossRefPubMedGoogle Scholar
- 18.Van Herreweghe J, Vanderkelen L, Callewaert L, Aertsen A, Compernolle G, Declerck P, Michiels C (2010) Lysozyme inhibitor conferring bacterial tolerance to invertebrate type lysozyme. Cell Mol Life Sci. doi: 10.1007/s00018-009-0241-x