Bacterial strategies to conceal the surface peptidoglycan

SCAN Seminar

Title: Bacterial strategies to conceal the surface peptidoglycan

Speaker: Sergio Raposo Filipe

Affiliation: Bacterial Cell Surfaces and Pathogenesis

Abstract:

Peptidoglycan (PGN) is a major component of the cell surface that surrounds bacterial cells and provides protection to the extreme osmotic forces they are subjected to. It is a heterogeneous polymer of glycan chains, produced by assembling of alternated beta-(1-4)-linked N-acetylglucosamine and N-acetylmuramic acid, and crosslinked by short peptides that can vary in length and aminoacid composition.

The organization of the bacterial cell surface varies greatly in Gram-negative and Gram-positive bacteria despite a relatively conserved chemical composition of their PGN. The small number of PGN layers found in Gram-negative bacteria seems inaccessible from the outside due to the presence of the outer membrane (made of lipopolysaccharides (LPS), phospholipids and surface proteins). In Gram-positive bacteria, wall teichoic acids, capsular polysaccharides and surface proteins can cover a much thicker macromolecule of PGN.

The synthesis of PGN is highly regulated to ensure the robustness of this polymer throughout the whole bacterial cell cycle. We are studying this process to determine whether an infected host can recognize assembled PGN incorporated into the bacteria cell wall.