PROTEOMIC ANALYSIS OF LISTERIA MONOCYTOGENES MUTANTS DEFECTIVE IN LPXTG PROTEINS

M. GRACIELA PUCCIARELLI; ENRIQUE CALVO; A. HENRIQUES; JAVIER FERNANDO MARISCOTTI; D. CABANES; FRANCISCO GARCÍA-DEL PORTILLO

GOTHENBURG

Congreso; 3rd Congress of European Microbiologists; 2009

The Federation of European Microbiological Societies (FEMS)

Background: Listeria monocytogenes is a Gram-positive bacterial pathogen that causes serious diseases in humans and animals. This pathogen has the ability of crossing diverse host defense barriers, as the intestinal epithelium, the placenta and the blood-brain barrier. Interestingly, the genome of L. monocytogenes contains a large set of genes (in the range of 40) encoding proteins that are anchored covalently to the peptidoglycan via the recognition of a conserved LPXTG motif. Some of the few proteins of this family characterized at the functional level include the invasin Internalin-A (InlA); Lmo0320 (Vip); and, InlJ, which promotes bacterial adhesion. The biological role of the rest of LPXTG proteins remains unknown. Objective: To apply proteomics to define the number of LPXTG proteins synthesized by L. monocytogenes in different environmental conditions as well as in mutants lacking concrete proteins of this family. Methods: Peptidoglycan and associated proteins were purified following published methods (Pucciarelli et al. Proteomics 2005, 5:4808-17) in bacteria growing either in brain-heart infusion (BHI) medium or inside epithelial cells. Results: To date, a total of five mutants defective in LPXTG proteins have been characterized by proteomics for the protein content in cell wall material. Differences in the relative amount of certain LPXTG proteins have been found in several of these mutants. The most profound change has been detected in a mutant lacking the LPXTG protein Lmo0842, which is deficient for certain LPXTG proteins identified in wild-type bacteria. The cell wall proteome in intracellular L. monocytogenes is currently under analysis. Conclusion: The absence of a specific LPXTG protein might trigger bacterial responses directed to attenuate the effect of such deficiency. This phenomenon supports the existence of regulatory processes that L. monocytogenes may use to dictate the panel of LPXTG proteins to be synthetized in a certain environment.