FIG. 2.

Qualitative (A and B) and quantitative (C) assays of piliation in N. meningitidis comP, pilT, pilT2, pilU, pilV, pilX, and pilZ mutants. The WT strain and a nonpiliated pilD mutant were included as positive and negative controls, respectively. (A and B) Tfp purified from the different strains using a “classical” shearing/ammonium sulfate precipitation method (A) or a shearing/immunoprecipitation method (B) were separated by SDS-PAGE and stained with Coomassie blue. Samples were prepared from equivalent numbers of CFU, and identical volumes were loaded in each lane. (C) Tfp were quantified by a whole-cell ELISA using a monoclonal antibody specific for strain 8013 fibers. Equivalent numbers of CFU were applied to the well of a microtiter plate, and Tfp were quantified by measuring the OD₄₅₀. Results are expressed as CFU mutant/CFU WT strain giving an OD₄₅₀ of 0.4 and are the means ± standard deviations from 4 to 12 independent experiments. Ratios for the WT strain (positive control) and the nonpiliated pilD mutant (negative control) have been set at 1 and 0, respectively. A ratio smaller than 1 indicates that the mutant is less piliated than the WT strain.