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

Fig 6

Immunogold-labelling of MDAΦ and type IV pili of material harvested from a flow chamber by aspiration.

Two antibodies were used: (i) the anti-MDAORF4 polyclonal antibody labelled with 8 nm-diameter gold particles and (ii) the monoclonal antibody 20D9 directed against the SB pilin variant and labelled with 12 nm-diameter gold particles. (A) Positive control, strain Z5463(SB-aph3’) grown under standard conditions. Left panel, bacteria are labelled by 12 nm beads corresponding to pili, the gray arrow points toward 12 nm beads. Right panel, bacteria surrounded only by filaments labelled by small particles corresponding to filamentous bacteriophages, the black arrow points toward 8 nm beads. (B) Material harvested from the biomass covering a monolayer of FaDu cells infected by Z5463(SB-aph3’) and labelled by the above two antibodies. Most of the material surrounding the bacteria are labelled by 8 nm particles and therefore correspond to filamentous bacteriophages (black arrow). No labelling with 12 nm beads corresponding to type IV pili was detected. (C) Global view of bacteria harvested from a flow chamber with enlargements. Only phage filaments are detected. Magnification is noted. Letters B in white label bacteria.

Fig 6

doi: https://doi.org/10.1371/journal.ppat.1006495.g006