STEC strain EDL933 colonization on fixed T84 intestinal epithelial cell layers under flow. (A) Graph showing the progression of bacterial growth on the surface. The data points represent mean values of the bacterial coverage in percent at 20 min intervals from four separate flow chamber runs. Error bars represent ±1 SD between individual flow chamber runs (shown, for clarity, only at 1-h intervals). Values at each 20-min time point obtained in each flow chamber run are mean values from recordings at 11 positions each representing 1,100 × 850 μm on the cell layer surface. The graph is based on a total of 2,684 single scans. (B–D) Examples of image data recorded at one representative 380 × 250 μm cropped position. Phase contrast microscopy (Bi–Biv), fluorescence microscopy (Ci–Civ), and software-detected coverage (Di–Div) are shown at four specific time points. These time points are marked with broken lines in (A) representing four phases of surface colonization; seeding (½h; Bi,Ci,Di), initial establishment on the surface (5 h; Bii,Cii,Dii), stabilization on the surface (9 h; Biii,Ciii,Diii), and steady state (17 h; Biv,Civ,Div). GFP, green fluorescent protein; h, hours; PH, phase contrast microscopy; ROI, region of interest.