FIG. 7.

Model of the regulatory network controlling curli production and biofilm formation in E. coli. Curli production at low osmolarity results from transcriptional activation of the csgD promoter by OmpR. When cells encounter high-salt medium, the Cpx pathway is activated. CpxR-P binds to the csgD promoter and consequently switches csgD expression off. The involvement of the regulatory systems EnvZ/OmpR, CpxA/CpxR, RcsC/RcsB, and H-NS in curli production is illustrated. Activation of all of these regulatory proteins is dependent on medium osmolarity. The different regulations are indicated by arrows for positive controls or via a line with a bar for negative controls. H-NS can exert either activation or repression, depending on the environmental conditions.