Figure 5.

ΔcsgB does not bind Congo red dye, does not form biofilm, and lacks curli fimbriae. (A) Bacterial overnight cultures of 43895 (WT), ΔcsgB, and the complement ΔcsgB(pcsgBA) were plated on Congo red indicator agar, incubated at 37 °C for 24 h, and examined visually. Colonies of ΔcsgB were less red than the colonies of the WT and ΔcsgB(pcsgBA) controls. (B) Bacterial cultures of the same strains were grown overnight, statically in LB at 37 °C. Medium was removed and pellicle-biofilms detected by staining with 1% crystal violet. The ΔcsgB culture did not form a pellicle-biofilm as did the cultures of the WT and ΔcsgB(pcsgBA) controls. Static overnight cultures of the same strains were individually applied on 300-mesh carbon-Formvar-coated copper grids and prior to EM examination (original magnification 10,000×) were (C) negatively stained with 1% phosphotungstic acid, pH 7.4 or (D) immunostained with rabbit anti-CsgA sera and goat anti-rabbit IgG conjugated with10-nm gold particles. Arrows point to anti-CsgA immunogold deposited onto curli fibers in the enlarged dash boxes. No curli fimbriae were detected with ΔcsgB.