Pili interfere with PorB_IA-dependent invasion.

<p>(<b>A</b>) Chang cells were infected with N2009 (PorB_IA, P⁺) or N2010 (PorB_IA, P⁻) at MOI 10 for 1 h and then analyzed by gentamicin protection assays. The number of adherent (white bars) and invasive (black bars) bacteria of the strain N2010 was taken as 100%. The graph shows mean values ± SD of two independent experiments performed in duplicates. (<b>B</b>) Intracellular N2009 are highly enriched for non-piliated variants. Piliated (white bars, Pili+) and non-piliated (black bars, Pili−) gentamicin resistant N2009 gonococci recovered from the experiment shown in (A) were quantified for their pilus phenotype with a steromicroscope. (<b>C</b>) Chang cells were infected at an MOI of 10 for 30 min with N927 (PorB_IA, P⁻) or with N2013 (<i>recA</i>ⁱ, PorB_IA, P⁺), a <i>rec</i>A mutant which cannot undergo <i>pil</i>E recombination. The bar chart shows the results of a gentamicin protection assay as the mean values ± SD of three independent experiments done in duplicates. The number of adherent (white bars) and invasive (black bars) bacteria of N927 was set to 100%. p<0.01: ** (<b>D</b>) Model of the molecular events underlying the switch from local to invasive gonococcal infection.