FIG. 4.

Fold change of gonococcal tonB and fur promoter region expression during N. gonorrhoeae infection of endocervical epithelial cells. N. gonorrhoeae GFP expressing strains (F62-rmpGFP, F62-furGFP, and F62-tonBGFP) were incubated with epithelial cells at an MOI of 100:1 (100 gonococci to 1 epithelial cell), and the cultures were examined at 1-, 2-, 4-, and 8-h intervals after infection for fold change in fur and tonB gene promoter expression compared to rmp gene promoter expression per each CFU. (A) Fold change determined for total bacteria (adherent plus intracellular); (B) fold change determined for intracellular bacteria only. Gene promoter expression was measured by using FACS analysis (CellQuest software, version 3.3). The fold change is expressed as the mean fold change ± the SD of three independently performed experiments (each performed in duplicate): the fur fluorescence fold change is represented by open bars, and the tonB fluorescence fold change is represented by black bars.