Figure 6. Proposed model of TviA-mediated changes in gene expression, which occur during the transition of bacteria from the intestinal lumen into tissue.

Due to elevated osmolarity, tviA is not expressed in the intestinal lumen, allowing expression of invasion genes (T3SS-1) and flagella. In the lamina propria, a relative decrease in osmolarity leads to the expression of tviA. Under these conditions, TviA is available as a co-repressor for RcsB, resulting in reduced invasion gene and flagellar gene expression and activation of genes in the viaB locus, resulting in capsule (Vi antigen) production.