THE FLUORESCENCE BRIGHTENER RYLUX BSU INDUCES DIMORPHISM IN BASIDIOBOLUS-RANARUM

The fluorescence brightener Rylux BSU (RRSU) showed an affinity for po lysaccharide components of cell walls and accumulated in the extension zones of hyphal apices in Basidiobolus ranarum. It inhibited the pola rized growth of mycelial hyphae and induced isotropic growth resulting in spherical thick-walled cells up to 456 mum in diameter. On the inn er cell wall surface, massive protuberances were formed. The cell wall and protuberances were positive in PAS and the Grocott method and sta ined with fluorochromes Blankophor BA, Calcofluor, Uvitex 2B, Rylux BS U and FITC-labeled WGA- and ConA-lectins. The WGA-FITC fluorescence in tensity of the wall's outermost layer, if not connected with neighbour ing cells, and the fluorescence intensity of the innermost layer and o f some protuberances mainly in their apical parts were on the average twice higher than the fluorescence intensity of the remaining wall mat erial. RBSU binding to the cell wall material was stable. The process of converting from polarized to isotropic growth was reversible, depen ding upon contact with RBSU-containing medium. Repeated transfers of c ells from RBSU-containing medium to an RBSU-free medium resulted ill t he development of apical swollen dumbbell-shaped cells.