[SCAN] Bacterial strategies to conceal an armor

SCAN

Title: Bacterial strategies to conceal an armor

Speaker: Sérgio Filipe

Affiliation: Bacterial Cell Surfaces and Pathogenesis Lab, ITQB NOVA

Abstract:

The ability of the immune system to react against invading bacteria is essential for survival of all organisms. For that purpose, higher organisms, from plants to animals, have specific receptors that recognize Pathogen-Associated Molecular Patterns (PAMPs), to initiate a cascade of events that eliminates the bacterial invader.

Peptidoglycan (PGN) is considered a bona fide PAMP. It is the principal constituent of most bacterial cell surfaces and forms a load-bearing protective mesh. Despite being a surface component, PGN is concealed by an outer membrane, in Gram-negative bacteria, or by layers of glycopolymers and proteins, in Gram-positive bacteria.

We have shown that the absence of wall teichoic acids results in increased binding of PGN perception systems directly to the bacterial surface and in the activation of the host defenses.

More recently, we have been enquiring how synthesis of Gram-positive PGN, which is required for bacterial division, is synchronized with synthesis of other surface glycopolymers.

In Streptococcus pneumoniae, a Gram-positive bacterial pathogen, synthesis of the capsular polysaccharide is a tightly regulated process to ensure survival within the infected host.

In this seminar, we will present data that support a mechanism to guarantee the full encapsulation of pneumococcal bacteria. This is mediated by the correct localization of Wze, an autophosphorylating tyrosine kinase, and Wzd, a membrane protein required for Wze autophosphorylation. When expressed simultaneously, these proteins localize to the bacterial division septum and guarantee the full encapsulation of pneumococcal PGN, which is essential for bacterial resistance to PGN hydrolases present in the surrounding medium and for the ability of bacteria to evade the host immune system.