Figure 1.

Strategy of recombinant spore-surface display. A) A gene fusion is constructed between DNA coding for a spore surface protein (gray) and for an antigen (black). The fusion is under the transcriptional and translational signals of the spore surface gene. B) The gene fusion is cloned into an integrative plasmid next to an antibiotic-resistance gene cassette (Ab^R) and between two parts of a non-essential gene of B. subtilis. The gene fusion is integrated on the B. subtilis chromosome by a double cross over between homologous DNA present on the integrative plasmid and on the chromosome, interrupting the non-essential gene. C) During sporulation the gene fusion is expressed in the mother cell and the chimera assembled around the forming spore. D) At the end of sporulation the mother cell lyses releasing the mature spore with the antigen stably anchored to its surface.