FIG 1.

CLSM analysis of HeLa cells infected by N. meningitidis strains. HeLa cells were infected with N. meningitidis serogroup B strain B1940. After application of gentamicin treatment to selectively kill extracellular bacteria, infected cells were analyzed by CLSM. Images were taken 7 h after infection. To detect intracellular bacteria, polyclonal antibody against a whole-cell preparation of N. meningitidis was used after permeabilization with saponin, in combination with FITC-conjugated secondary antibody. To detect cellular markers (actin, α-tubulin, and transferring receptor), we used Alexa 568 phalloidin (a and b), anti-α-tubulin (c), or anti-transferrin receptor (d) antibody in combination with TRITC-conjugated secondary antibody. Merged images of the different channels are shown. Bars, 10 μm. Panels a and b are different views of the same bacteria infecting phalloidin-stained HeLa cells.