FIG. 7.

Model of SPI2 signaling. Different colors indicate different two-component systems. The primary signals are detected by the EnvZ sensor kinase and are independent of acetyl phosphate signaling. PhoPQ is unlikely to directly regulate SPI2. Question marks indicate unknown phosphorylation states of response regulators. Much of the work that was used to synthesize this model is not cited; for this we apologize to the authors of relevant work. The asterisk indicates unphosphorylated OmpR at the ompF promoter in order to reflect the predominance of OmpF expression in conditions under which OmpR is predominantly unphosphorylated; however, the regulation at the porin promoters is considerably more complex than that depicted.