Fig. 7.
A novel antigen delivery and release system in E. coli. (A) Iron-rich conditions. In iron-rich medium, the iron-Fur complex binds to the Fur box of PviuB and represses the transcription of the E gene, while the antigen gene is expressed under control of the IPTG-inducible T7 promoter. (B) Iron-limiting conditions. In the host organism, antigen gene expression is repressed by LacI in the absence of IPTG. Meanwhile the iron-Fur complex is dissociated and the transcription of the E gene initiated. Bacterial cells are rapidly lysed by protein E to achieve antigen release and biological containment.