Sustained delivery of SopB into epithelial cells by <i>Salmonella</i>.

<p>Time course of SopB delivery in HeLa cells. Monolayers infected with <i>Salmonella sopB</i>^3xFLAG were fixed and immunostained for bacteria (αCSA) and effector (αFLAG). (A) The percentage of effector-positive infected cells was quantified. Means ± SD from 3 independent experiments. (B) Representative confocal images of <i>Salmonella</i>-infected HeLa cells with SopB^3xFLAG staining. Scale bars: 10 μm; inset 2 μm. (C) Analysis of intracellular <i>Salmonella</i> populations in SopB^3xFLAG-positive cells. Effector-positive cells were classified according to the presence or absence of cytosolic bacteria. Means from 3 independent experiments. Statistical significance was analyzed by unpaired Student’s <i>t</i>-test. *** P ≤ 0.001, ns = not-significant. (D) Representative confocal images of HeLa cells infected with <i>Salmonella sopB</i>^3xFLAG subjected to differential permeabilization. Cytosolic (Cyto.) bacteria (red) and the cytosolic tail of calnexin (yellow, permeabilization control) were labeled after digitonin permeabilization. Total bacteria (grey) and SopB^3xFLAG (green) were detected post saponin permeabilization. Scale bars: 10 μm; inset 2 μm. See also <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006354#ppat.1006354.s001" target="_blank">S1 Fig</a>.