FIG. 8.

Model for processing environmental signals that affect SPI-1 invasion gene expression. An environmental signal activates (or deactivates) FimYZ, which then activate (or deactivate) hilE transcription. Activation of fimYZ also leads to expression of type 1 fimbriae and an adhesive phenotype. The activation of hilE transcription produces HilE protein, which then leads to repression of hilA expression and subsequent expression of the other SPI-1 genes through its interaction with the HilD regulatory protein.