MC58Δ gapA-1 has a reduced ability to associate with HBMEs compared to the wild-type or complemented strains. The number of GapA-1-deficient meningococci associating was significantly lower than the wild-type (*P = 0.0018). Mean levels shown from three independent experiments, each using triplicate wells. Bars denote standard deviation. Cfu denotes colony forming units.