Hyperblebbing

1. A Shigella bacterium which expresses TolA, TolB, TolQ, and Pal proteins, does not express TolR protein, and does not express a native Shigella lipopolysaccharide , wherein the bacterium is Shigella sonnei or Shigella flexneri , and, during growth in culture medium, releases greater quantities of outer membrane blebs into the medium than the same bacterium expressing all of TolA, TolB, TolQ, TolR, and Pal proteins.

2. The Shigella bacterium of claim 1 , which is a ΔtolR strain of Shigella.

3. The Shigella bacterium of claim 2 , wherein the bacterium does not express a native Shigella lipopolysaccharide and does not express a native Shigella O antigen.

4. The Shigella bacterium of claim 1 , wherein the TolA, TolQ, and/or Pal protein is located in the bacterium's inner or outer membrane.

5. The Shigella bacterium of claim 1 , wherein the Shigella bacterium additionally does not express a Shigella enteric toxin.

6. The Shigella bacterium of claim 1 , which does not express the functional HtrB enzyme.

7. The Shigella bacterium of claim 6 , which is a htrB knockout.

8. The Shigella bacterium of claim 2 , wherein the bacterium is of a ΔtolRΔgalU strain.

9. The Shigella bacterium of claim 2 , wherein a stxA and/or stxB gene is inactivated.

10. Culture medium comprising a bacterium of claim 5 , which has been grown under conditions which permit the release of blebs into the medium by the bacterium.

11. A method of producing Shigella sonnei or Shigella flexneri blebs, comprising culturing the bacterium of claim 1 in a culture medium under conditions which permit the release of blebs into the medium by the bacterium and separating the released blebs from the culture medium.

12. The method of claim 11 , wherein the bacterium has been grown under iron-limiting conditions.