Cytochemical detection of polysaccharides and the ultrastructure of the cell coat of zoospores of Chytriomyces aureus and Chytriomyces hyalinus

The formation and structure of cell coats on zoospores of Chytriomyces aureus and C. hyalinus are described from an ultrastructural and cytochemical study. After zoospore initials are cleaved, but before organelles are organized into the arrangement found in free-swimming zoospores, dictyosomal vesicles deposit a cell coat on the outer surface of the plasma membrane. In free-swimming zoospores, the cell coat covers all of the zoospore except the flageUar sheath. The inner layer of the cell coat is homogeneously dense and is covered with an outer layer of helically arranged spines. Both layers of the cell coat stain with the silver methenamine technique for polysaccharides, as do glycogen and fibril-containing vesicles in the cytoplasm. Sodium bisulfite and hydrogen peroxide controls confirm the polysaccharide specificity of the reaction in glycogen deposits, vesicles, and the outer layer of the cell coat. Use of the sulfhydryl blocking agent, iodoacetate, demonstrates sulfhydryl-containing compounds in the inner layer of the cell coat.