FIG. 4.

β₁-Chain integrins are not required for EPEC-mediated actin polymerization. DKO (β₁⁺) (A and B) or TKO (β₁⁻) (C and D) cells were infected at an MOI of 20 with EPEC strain JPN15/pMAR7 expressing green fluorescent protein (GFP) for 6 h at 37°C. Monolayers were washed and permeabilized, and microscopic fields were then examined for the presence of GFP-expressing bacteria (A and C) or were stained with tetramethylrhodamine isothiocyanate(TRITC)-labeled phalloidin to visualize F-actin (B and D). Arrows indicate examples of colocalized bacteria and F-actin. Magnification, ×1,000.