FIG. 1.

The current model of ompF and ompC regulation. According to this model, the differential expression of ompF and ompC is a direct consequence of the intracellular concentrations of the phosphorylated form of OmpR, OmpR-P. Under low-osmolarity conditions, low levels of OmpR-P are present in the cell, resulting in an OmpF⁺ OmpC⁻ phenotype. Under high-osmolarity conditions, high levels of OmpR-P are present in the cell, resulting in an OmpF⁻ OmpC⁺ phenotype. The relationship between porin expression and the concentration of OmpR-P is based on the mathematical modeling of Russo and Silhavy (22). This figure has been adapted from reference 21.