FIG 3.

Δstmp1 mutant bacteria have a functional T4BSS. Intracellular cAMP levels were determined following infection of HeLa cells with C. burnetii WT, ΔdotA (T4BSS mutant), or the Δstmp1 mutant expressing CyaA alone or fused to CvpA (T4BSS effector protein). The expression of each C. burnetii transformant was confirmed by Western blotting analysis (data not shown). Results are expressed as the fold change over cAMP levels obtained from infection with C. burnetii expressing CyaA alone. Compared to the C. burnetii ΔdotA T4BSS mutant, both C. burnetii WT and Δstmp1 mutant bacteria secrete CyaA-CvpA into the host cytoplasm. Data are shown as the mean ± SEM of six independent experiments. Statistical significance was determined by one-way ANOVA with Tukey’s post hoc test.