Vacuolar structure in the C. albicans sur7 Δ mutant. (A) Carboxy-DCFDA was used in addition to FM4-64 to differentiate between vacuolar and non-vacuolar structures stained by FM4-64 in C. albicans yeast cells. Upon active endocytosis, FM4-64 stains the vacuolar membrane whereas CDCFDA is passively diffused into the cell and into the vacuolar lumen. Images were taken following sufficient incubation that allowed each dye to reach the vacuole. (B) Thin-section electron micrographs of yeast cells of the wild-type and sur7 Δ null mutant strains are shown with arrows indicating abnormal invagination of the plasma membrane and subcellular structures of plasma membrane origin. A size bar is shown to indicate 1 μm.