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A virulence-associated filamentous bacteriophage of Neisseria meningitidis increases host-cell colonisation

Fig 5

Detection of phage particles and type IV pili in bacteria colonizing the epithelial cell monolayer.

Monolayers of FaDu cells in a flow chamber were infected either with the wild-type strain Z5463(SB-aph3’) (A) or with the MDAΦ deleted strain (Z5463(SB-aph3’)ΔMDA) (B) under constant flow for 18 hours. Bacteria were then aspirated from the flow chamber leaving bacteria adhering onto the apical surface of the epithelial cells. The material recovered by aspiration ((1) top panel) and the remaining bacteria adhering onto the monolayers ((2) bottom panel) were stained by immunofluorescence using the anti MDAORF4 polyclonal antibody (in green) and the 20D9 monoclonal antibody (in red). With both strains, bacteria that have not been harvested are covering the host cells. These bacteria are heavily piliated, and in the case of the WT strain very few phage particles were detected on this material, the green staining which corresponds to bacteriophages represents less 6% of the red surface which correspond to the pili staining. On the other hand, in the material harvested by aspiration corresponding to the upper layers of the biomass, bacteria are surrounded by large quantity of bacteriophages (the red staining which corresponds to the pili represents 25% of the green surface which corresponds to the phage). (C) (1) Left pane, XZ section of a monolayer of FaDu cells in a flow chamber infected with the wild-type strain Z5463(SB-aph3’) for 18 hours. Right panel XZ section of a monolayer of FaDu cells in a flow chamber infected with the MDAΦ deleted strain (Z5463(SB-aph3’)ΔMDA) for 18 hours. (2) XZ section of a monolayer of HDMEC cells in a flow chamber infected with the wild-type strain Z5463(SB-aph3’) for 18 hours. (3) XZ section of a fixed monolayer of HDMEC cells in a flow chamber infected with the wild-type strain Z5463(SB-aph3’) for 18 hours. The biomass was stained by immunofluorescence using the anti-MDAORF4 polyclonal antibody (in green), the 20D9 monoclonal antibody (in red) and DAPI in blue.

Fig 5

doi: https://doi.org/10.1371/journal.ppat.1006495.g005