RAC1 and infection: Consistently with this requirement for Rho GTPases, pedestal formation (Fig. 4B) and attachment (Fig. 4C) by WT EPEC were significantly impaired in either Cdc42 knockout Hap1 cells (ΔCdc42) or WT Hap cells treated with the Rac1 inhibitor EHT1864 (Rac1 knockout Hap1 cells are severely compromised in adhesion to culture dishes and therefore could not be used for infection assays).