Fig. 5. Transferrin-iron uptake by the wild-type and mutant gonococcal strains.

Gonococcal strains were grown in iron-depleted conditions, standardized to culture density and then incubated with transferrin-⁵⁵Fe for 30 min. Unincorporated ⁵⁵Fe was removed by filtration, followed by scintillation counting of extracted filters containing gonococcal strains. The specific amount of iron internalized by each strain was standardized to the wild-type strain, resulting in the relative iron uptake values shown on the y-axis. The each bar represents the mean and standard deviation from the mean generated from three independent assays. Asterisks represent those comparisons in which statistical significance (P-value <0.05) was reached in pairwise comparisons between wild-type and mutant strains using an unpaired student’s t-test.