AmpA overexpression increases the rate of endocytosis but notexocytosis. A) FITC dextran was added to cells in shakingculture to a final concentration of 2 mg/ml. Aliquots were taken everytwenty minutes and prepared as described in methods. Fluorescence wasread on a Bio-Rad fluorimeter. B) Cells in shaking culture wereincubated in FITC dextran as in A. They were then washed toremove extracellular FITC. Aliquots were taken every twenty minutes. Theamount of FITC dextran present at Time = 0 was labeled as 100% for eachcell type, and the FITC dextran remaining in the cell was taken as apercentage of the original amount. For A and B,error bars represent the standard error of the mean. The data representthe averages of a minimum of 5 separate determinations done on differentdays. C and D) Overexpression of ampA causes multipleendocytic cups to form repeatedly at the same site. C) Wt andD) AmpA overexpressing cells containing the blasticidinresistant ABD-GFP plasmid were placed in chambered cover slipsovernight. Images were taken every 20 seconds for 5 minutes. Theseimages are representative slices from the time courses. Calibration bar= 6 um. Images of additional AmpA overexpressing cells undergoingendocytosis are shown in Additional file 14.