FIG. 3.

Yersinia can secrete Tir independent of Orf19 and CesT. (A) Y. pseudotuberculosis (YPIII) and the isogenic YPIII/pIB29MEKA mutant strain (YE/HMEKA, with the deletion of yopH, yopM, yopE, yopK, and ypkA) with or without pSK-HSV3 (orf19 tirHSV cesT) were grown in modified BHI medium at 26°C (left panel) or subsequently shifted to 37°C (right panel), which induces type III secretion. Supernatant samples were concentrated, resolved by SDS-PAGE (12% acrylamide), and visualized by Coomassie staining. The position of the secreted TirHSV band is indicated with an arrow, while those of the molecular mass standards (in kilodaltons) are shown at the right. (B) YE/HMEKA strains carrying various plasmids (see below and Fig. 4) were grown in modified BHI medium and induced for type III secretion as described above. Cell and supernatant samples were isolated, resolved by SDS-PAGE (8% polyacrylamide), and visualized by Coomassie staining (top panels) or Western analysis (bottom panels) probing with anti-HSV antibodies. Two secreted forms of TirHSV (TirHSV and TirHSV∗) are indicated by arrows, with the position of the YopD-YopN doublet highlighted with an arrowhead. + and − indicate the presence or absence of the indicated gene product, respectively.