Electron microscopic evidence of Phosfon D-induced alterations in the membranes of the dermatophytic fungus Microsporum cookei.

The dermatophytic fungus Microsporum cookei was cultivated for 24 h in the presence of subinhibitory and inhibitory concentrations (50 and 100 micrograms/ml) of Phosfon D, a growth retardant for higher plants also affecting fungal development, and its toxic effects were examined at the ultrastructural level. In both treatments, Phosfon D attacked the membranes, whose structural integrity was clearly compromised with damage of particular severity to mitochondria, nuclei and endoplasmic reticulum. In the instance of fungal growth suppression, the compound also caused plasmolytic and autolytic phenomena, sometimes accompanied by plasma membrane breakages. The submicroscopic effects observed confirm that Prosfon D is an antifungal compound which displays its toxic effects in the area of lipid metabolism, probably preventing the synthesis of fundamental components of the cellular membranes, such as unsaturated fatty acids and sterols.