A New Family of Lysozyme Inhibitors Contributing to Lysozyme Tolerance in Gram-Negative Bacteria

PLoS Pathogens

Johan Robben¹  Kristof G. A. Vanoirbeek²  Lien Callewaert²  Daphne Deckers²  Dorothy Nakimbugwe²  Chris W. Michiels²  Abram Aertsen²  Lise Vanderkelen²  Barbara Masschalck²  Joris M. Van Herreweghe² 

[1] Biomedical Research Institute (BIOMED), Hasselt University and Transnationale Universiteit Limburg, School of Life Sciences, Diepenbeek, Belgium;Laboratory of Food Microbiology, Department of Microbial and Molecular Systems (M2S), Katholieke Universiteit Leuven, Leuven, Belgium

关键词: Pseudomonas aeruginosa;    Bacterial pathogens;    Outer membrane proteins;    Peptidoglycans;    Protein extraction;    Gram negative bacteria;    Salmonella typhimurium;    Antibacterials;   

DOI  :  10.1371/journal.ppat.1000019

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Lysozymes are ancient and important components of the innate immune system of animals that hydrolyze peptidoglycan, the major bacterial cell wall polymer. Bacteria engaging in commensal or pathogenic interactions with an animal host have evolved various strategies to evade this bactericidal enzyme, one recently proposed strategy being the production of lysozyme inhibitors. We here report the discovery of a novel family of bacterial lysozyme inhibitors with widespread homologs in gram-negative bacteria. First, a lysozyme inhibitor was isolated by affinity chromatography from a periplasmic extract of Salmonella Enteritidis, identified by mass spectrometry and correspondingly designated as PliC (periplasmic lysozyme inhibitor of c-type lysozyme). A pliC knock-out mutant no longer produced lysozyme inhibitory activity and showed increased lysozyme sensitivity in the presence of the outer membrane permeabilizing protein lactoferrin. PliC lacks similarity with the previously described Escherichia coli lysozyme inhibitor Ivy, but is related to a group of proteins with a common conserved COG3895 domain, some of them predicted to be lipoproteins. No function has yet been assigned to these proteins, although they are widely spread among the Proteobacteria. We demonstrate that at least two representatives of this group, MliC (membrane bound lysozyme inhibitor of c-type lysozyme) of E. coli and Pseudomonas aeruginosa, also possess lysozyme inhibitory activity and confer increased lysozyme tolerance upon expression in E. coli. Interestingly, mliC of Salmonella Typhi was picked up earlier in a screen for genes induced during residence in macrophages, and knockout of mliC was shown to reduce macrophage survival of S. Typhi. Based on these observations, we suggest that the COG3895 domain is a common feature of a novel and widespread family of bacterial lysozyme inhibitors in gram-negative bacteria that may function as colonization or virulence factors in bacteria interacting with an animal host.

【 授权许可】

CC BY