Fig. 3. Internalization of FimCH-coated beads. 5637 cells were incubated with FimCH- or BSA-coated beads for 30–60 min and then processed for SEM (A–C) or TEM (D–G). (A and B) FimCH-coated beads were internalized efficiently by 5637 cells, while the few adherent BSA-coated beads (C) did not induce any appreciable alterations in the 5637 cell membrane. (D–G) The host cell membrane appears to zipper around and eventually envelope FimCH-coated beads during the internalization process. Scale bars represent 5.0 µm (A and E), 0.5 µm (B–D) and 1.0 µm (F and G).