Yersinia Pathogenesis and Evolution
Pathogenic Yersinia include Y. enterocolitica and Y. pseudotuberculosis, which cause gastroenteritis, and Y. pestis, which causes plague. All are zoonotic pathogens. Y. pestis evolved from its Y. pseudotuberculosis lineage very recently. They remain very similar genetically.
Y. pestis is transmitted by fleas. It must resist the immune defenses of fleas to grow without killing the fleas, and form a biofilm in the proventriculus in order to be transmitted. Y. pseudotuberculosis also forms biofilms, but we have uncovered some key differences in their biofilm strategies.
Y. pestis biofilms are held together by a polysaccharide matrix (Hms-ECM). Y. pseudotuberculosis also produces Hms-ECM, but not nearly as much as Y. pestis. We have found a protein called YadE that is important for making Y. pseudotuberculosis biofilms cohesive. Y. pestis has lost the yadE gene.
Expression of YadE appears to be controlled by the Rcs phosphorelay , as well as the Csr cascade. We are trying to work out the details of how YadE functions and how its expression is regulated in Y. pseudotuberculosis.