Figure 3.

Effect of a null mutation in sopE on the interaction of S. typhimurium with Henle-407 cells. (I) Cultured Henle-407 cells were infected with S. typhimurium for 15 min, fixed, and stained with rhodamine-labeled phalloidin to visualize the actin cytoskeleton (A) and with a fluorescein isothiocyanate (FITC)-labeled antibody directed to S. typhimurium to visualize bacteria (B). (C) Phase-contrast images of the same cells. (Micrographs obtained with a ×40 objective.) (II) Internalization of the S. typhimurium sopE mutant into Henle-407 cells. Bacterial internalization levels, measured by microscopy as indicated in the text, were standardized to wild-type S. typhimurium. At a minimum, 300 cells were scored for each strain. The standard deviation of these experiments was less than 10%. The strains were as follows: wild type, SL1344; sopE, SB757; sopE (psopE), SB757 (pSB1130); invG, SB161.