FIG. 6.

In vitro growth competition between wild-type and ΔfauA2 B. pertussis strains in iron-replete and iron-restricted SS broth. (A) Ethidium bromide-stained gel showing relative yield of 430-bp fauA⁺- and 175-bp ΔfauA2-specific PCR products coamplified from DNA prepared from mixed-strain cultures in iron-replete and iron-restricted SS broth. Mut, mutant; WT, wild type; MW, size markers. (B) Mean CI values (n = 3) (y error bars representing ±1 standard deviation are hidden by the symbols) derived from ΔfauA2/fauA⁺ DNA copy number ratios determined by fluorescence image analysis. Filled squares, iron-replete conditions; open squares, iron-restricted conditions. The dashed line (y value of 1.00) corresponds to the hypothesized CI value if there was no difference in fitness between the strains cocultured under the specified conditions.