M. Graciela Pucciarelli,1* Hélène Bierne2, and Francisco García-del Portillo1*
1 Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CSIC), Darwin 3, 2SG49 Madrid, Spain
*e-mail: [email protected], [email protected] 2Unité des Interactions Bactéries-Cellules, Institut Pasteur, INSERM UôG4, INRA USC2G2G, 2S Rue du Docteur Roux, 75724 Paris cedex 15, France e-mail: [email protected]
Listeria monocytogenes contains a cell wall formed by a multilayered cross-linked peptidoglycan decorated with teichoic and lipoteichoic acids. Like in all eubacteria, the cell wall of L. monocytogenes plays a critical role in its physiology since it ensures integrity of the cell while maintaining a high internal osmotic pressure. In addition, it also endows the cell with a specific cell shape and provides protection against mechanical stress. As in other noncapsulated grampositive bacteria, the cell wall of L. monocytogenes is the outermost structure of the cell and acts as a scaffold in which different proteins anchor. L. monocyto-genes is a highly successful pathogen that invades eukaryotic host cells, crosses several natural barriers of the host and survives to extreme environments, and its cell wall must necessarily contain molecules making possible the colonization of these niches. The role in pathogenesis of some of these surface molecules is just starting to be deciphered. Likewise, the genome sequences now known for a few L. monocytogenes strains reveal that this pathogen has a large number of genes encoding proteins with domains mediating interactions with cell-wall polymers. Some of these cell-wall-associated proteins are currently subjected to intense investigation. Recent studies have also revisited the structure of the peptidoglycan of L. monocytogenes and unravelled new modifications in its structure that may be important for pathogenicity.
In this chapter, we summarize the current knowledge of the biochemistry and enzymology of the L. monocytogenes cell wall. Moreover, we discuss on the plethora of proteins that attach to cell-wall components, making emphasis in the distinct modes of protein-cell-wall association and their role in virulence. We also describe recent proteomics studies that have facilitated the identification of novel L. monocytogenes surface proteins predicted by the genome data. Finally, we briefly describe what is known on the role of L. monocytogenes cell-wall components in the modulation of the host immune response.
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