Extracellular Bacterial Pathogen Induces Host Cell Surface Reorganization to Resist Shear Stress

Guillain Mikaty,Emilie Mairey,Nelly Henry,Philippe Morand,Marie Christine Prévost,Dave Dyer,Katrina T Forest,Magali Soyer,Stéphanie Guadagnini,Guillaume Duménil,Xavier Nassif,H Steven Seifert

doi:10.1371/journal.ppat.1000314

Abstract

Bacterial infections targeting the bloodstream lead to a wide array of devastating diseases such as septic shock and meningitis. To study this crucial type of infection, its specific environment needs to be taken into account, in particular the mechanical forces generated by the blood flow. In a previous study using Neisseria meningitidis as a model, we observed that bacterial microcolonies forming on the endothelial cell surface in the vessel lumen are remarkably resistant to mechanical stress. The present study aims to identify the molecular basis of this resistance. N. meningitidis forms aggregates independently of host cells, yet we demonstrate here that cohesive forces involved in these bacterial aggregates are not sufficient to explain the stability of colonies on cell surfaces. Results imply that host cell attributes enhance microcolony cohesion. Microcolonies on the cell surface induce a cellular response consisting of numerous cellular protrusions similar to filopodia that come in close contact with all the bacteria in the microcolony. Consistent with a role of this cellular response, host cell lipid microdomain disruption simultaneously inhibited this response and rendered microcolonies sensitive to blood flow–generated drag forces. We then identified, by a genetic approach, the type IV pili component PilV as a triggering factor of plasma membrane reorganization, and consistently found that microcolonies formed by a pilV mutant are highly sensitive to shear stress. Our study shows that bacteria manipulate host cell functions to reorganize the host cell surface to form filopodia-like structures that enhance the cohesion of the microcolonies and therefore blood vessel colonization under the harsh conditions of the bloodstream.

Highlights

Infectious diseases leading to colonization of the blood by the infectious agent are a major burden to society
We previously showed that N. meningitidis growing in tight bacterial aggregates on eukaryotic cellular surfaces are highly resistant to external forces exerted by the harsh conditions found in the nasopharynx or in the bloodstream [4]
N. meningitidis form bacterial aggregates of different sizes, spontaneously and independently of the adhesion to host cells; this process depends on type IV pili

Summary

Introduction

Infectious diseases leading to colonization of the blood by the infectious agent are a major burden to society Such infections lead to devastating clinical manifestations including septic shock, hemorrhagic syndromes or infection of the brain (meningitis). The common characteristic of these pathogens is their presence in the bloodstream at a given point of the infection process Such pathogens are exposed to mechanical forces exerted by the blood flow, which follows a complex pattern throughout different blood vessels. This specific environment is increasingly recognized as a determining factor during pathogenesis and implies an adaptation of the pathogens [1,2,3]. One such infectious agent, used as a model in this study, is the Gram-negative bacteria Neisseria meningitidis [4]

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