Sequential action of cell wall hydrolases in the germination and outgrowth of Microsporum gypseum macroconidia.

Abstract

The spore coats of mature macroconidia of Microsporum gypseum contained greater carbohydrate–protein ester, disulfide, acid-soluble phosphate, and acid-insoluble phosphate content than mycelial walls. Phosphate was a major constituent of the spore coat, accounting for 6.8% of the dry weight. Spore coat phosphates were located internally as acid-insoluble phosphate, or externally on the spore surface as acid-soluble phosphate. Upon spore germination, the carbohydrate–protein ester, acid-insoluble phosphate, and acid-soluble phosphate content of the spore coats decreased, resulting in considerable alteration of spore coat internal and external properties. Germination was initiated by early alkaline protease and β-1,3-glucanase action, followed by ethyl-esterase, phosphodiesterase, and chitinase activities. These hydrolases were compartmentalized in lysosomal vesicles, which appeared to be delivered to the germinating spore in a coordinated manner.