Fig. 2. The Arp2/3 complex is required for efficient bacterial internalization. (A) Extracellular Rickettsia conorii (arrow), but not intracellular bacteria (arrowhead) strongly colocalizes with Arp3, suggesting that Arp2/3 recruitment plays an essential role in the uptake process in Vero cells. (B) Transfection of the WASp-related protein, Scar (Scar FL), and the Arp2/3 binding domain (Scar WA) inhibits the ability of R. conorii to enter Vero cells, but has no effect on bacterial adherence (data not shown). Bar, 2 µm.