Ultrastructural detection of polysaccharides in the cell walls of two members of the Hyphocytriales

Abstract

Cytochemical methods that employed observation of lectin- or enzyme-gold complexes with an electron microscope were used to study the occurrence and distribution of sugars and polysaccharides in the cell walls of Rhizidiomyces apophysatus and Hyphochytrium catenoides , two fungi belonging to the class Hyphochytriomycetes. Both fungi have the polysaccharides cellulose and chitin in their cell walls and a minor component that contains n -acetyl- d -galactosamine. The discharge tubes emanating from sporangia of R. apophysatus stained positively for chitin but were negative for cellulose and the N -acetyl- d -galactosamine containing compound. Whereas the cell walls of developing sporangia of H. catenoides labelled strongly for cellulose, the results indicated they contained only trace amounts of chitin. The rhizomycelial walls of H. catenoides had a composition similar to that of the sporangia except for the septa that appeared to contain more sites indicative of chitin. The significance of the results relative to earlier studies of these fungi and generalizations with respect to cell wall chemistry and systematic relationships is discussed.