FIG. 3.

Cytotoxicity of J774A.1 macrophages caused by selected Y. enterocolitica mutants under conditions that promote the function of the Ysa TTS system. Mutations in genes involved in Ysa TTS affect the ability of Y. enterocolitica to induce cytotoxicity in J774A.1 macrophages. Following the initiation of infections, macrophages were incubated at 26°C under 5% CO₂ for 2 h. After this infection period, gentamicin was added at a final concentration of 100 μg/ml and cells were incubated at 37°C under 5% CO₂ for an additional 3 h. Cytotoxicity was determined by release of LDH. Strains of Y. enterocolitica (described in Table 1) are indicated from left to right: JB580v (wild type), YVM356 (yscR), GY4428 (ysaV), GY1087 (yscR, ysaV), GY4641 (ysaE), GY4668 (orf6 orf7), GY4665 (ysaC), GY4639 (ysaR), GY4664 (ysaU), GY4742 (ysrS), GY4613 (rcsB), and GY4531 (crp). A detailed protocol and description of calculations are presented in Materials and Methods. The results are displayed as means ± standard deviations of results of four individual assays preformed in triplicate.