Morphological and immunocytochemical appearance of EBEC cultures on solid supports in serum-free and serum-containing medium. [a-b/c-d] Phase contrast microscopy of EBEC cultures 2 days after plating (objective magnification: ×10) and at confluence (objective magnification: ×4) in serum-free (a-c) and serum-containing (b-d) medium. Inset in picture b shows single cells grown in the presence of serum forming fine interconnecting cytoplasmic bridges (objective magnification: ×40). [e-f] Representative immunocytochemical staining of confluent EBEC cultures grown on glass cover slips for the epithelial cell markers cytokeratins 5/6/18, showing localization of the green positive signal in the cytoskeleton of cells grown in both serum-free (e) and serum-containing (f) medium (objective magnification: ×20). In the insets, nuclei are blue stained with DAPI (original objective magnification: × 40). [g-h] Representative immunocytochemical staining of confluent EBEC cultures grown on glass cover slips for the tight junction protein ZO-1, showing spot-like green fluorescent signal in cytoplasm of cells cultured in serum-free medium (g) and circumferential localization of the green positive signal in cells cultured in serum-containing medium (h) (objective magnification: ×40). Nuclei are blue stained with DAPI.