Changes in the plasma membrane of regenerating protoplasts of Candida albicans as revealed by freeze-fracture electron microscopy.

Modifications occurring in the plasma membrane and their relationship to newly synthesized microfibrils were examined in regenerating protoplasts of Candida albicans by freeze-fracture electron microscopy. Freshly prepared protoplasts showed no residual wall material, and long invaginations covered the surface of the plasma membrane. Analysis of the external face (E-face) of the plasma membrane showed a significant decrease in the number of intramembranous particles (IMP) in comparison with the original cells. After 40 min incubation in regeneration medium, newly synthesized microfibrils which seemed to originate from protrusions in the plasma membrane were observed. The plasma membrane showed important modifications with respect to IMP. After 3 h 45 min, the cells were covered by an abnormal wall which showed isolated fibrils partially embedded in the matrix material. The plasma membrane of these partially regenerated protoplasts was similar to that of original cells. After 8 h, regeneration of the protoplasts seemed to be complete as no differences from the original cells were detected in the plasma membrane or the wall. Calcofluor white altered the deposition of wall polymers during regeneration, but did not modify the plasma membrane of the protoplasts.