Fig 7. The expression of T6SS-4 is induced in macrophages and Yptb mutants lacking T6SS-4 or its substrate YezP are defective in virulence against mice.
A. The expression of yezP and T6SS-4 is induced in macrophages. Wild-type Yptb was used to infect bone marrow-derived macrophages at an MOI of 10 for 15 or 30 min, and the expression of yezP, clpV4 and vgrG4 was measured by qRT-PCR. Bacteria grown in YLB were used as controls. Data shown were the average of three independent experiments; error bars indicate SD from three independent experiments. ***, p<0.001; *, p<0.05. Statistic analyses were performed by Student’s t-test. B. Bacterial strains grown in YLB were washed twice in sterilized PBS and used for orogastric infection of 6–8 weeks old female C57BL/6 mice using a ball-tipped feeding needle. For survival assays 3×109 bacteria of each strain were applied to different groups of mice (n = 10/strain), and the survival rate of the mice was determined by monitoring the survival daily for 3 weeks. Similar results were obtained in three independent experiments, and data shown are from one representative experiment done in triplicate. **, p<0.01; *, p<0.05. Statistic analyses were performed by Log-Rank test.