Different aspects of CNF1 activity on epithelial cells. (a-b) Transmission electron micrographs showing: a control mononucleated cell (a), and a CNF1-treated cell (b), bearing four nuclei in the cytoplasm. (c-d) Fluorescence micrographs of control (c) or CNF1-treated (d) cells stained for F-actin detection. CNF1-treated cells display polymerization of actin into stress fibers (asterisks) and prominent ruffles (arrows). (e-f) Scanning (e) and transmission (f) electron micrographs showing different stages of the internalization process of non-invasive bacteria by CNF1-treated cells. After being contacted by membrane ruffles (e), bacteria are internalized within vacuoles (f). (g-h) Fluorescence micrographs of cells stained with an antibody that recognizes tubulin, the main component of microtubules. Note in h, an example of multipolar mitosis induced by CNF1. (i-l) Fluoresce micrographs of control (i) and CNF1-treated (l) cells transfected with the Ds-Red plasmid to visualize mitochondrial organization. CNF1 induces the formation of elongated and interconnected mitochondria.