Location and biochemical nature of surface components reacting with concanavalin A in different cell types of Sporothrix schenckii

Surface components of cell walls of hyphae, conidia, and yeast-like forms of Sporothrix schenckii react with concanavalin A (Con A). By use of fluorescein-conjugated Con A, and a cytochemical method using the horseradish peroxidase technique, it was observed that the yeast-like forms reacted more strongly with Con A as compared with the mycelium. These studies demonstrated the presence of a thick Con A-binding layer in the cell wall of the yeast-like forms. In some instances, this layer was resolved into a basal and an outer sublayer. The reactivity of the latter with Con A differed in the two strains examined: In strain 1099.12, all yeast cells reacted uniformly with Con A, whereas, in strain 1099.18, the reactivity of the outer sublayer in different yeast cells ranged from weak or negative to strongly positive. The reactivity with Con A was probably due to peptido-rhamnomannans since such complexes extracted from both strains precipitated Con A and agglutinated a mannose-sensitive fimbriated Escherichia coli K12. The corresponding rhamnomannans obtained by hot alkali extraction of S. schenckii , which did not contain terminal nonreducing α- d -mannopyranose units, were unreactive with Con A. Reaction of the peptido-polysaccharides with Con A probably reflects the presence in variable proportions, depending on strain and growth conditions, of serine- or threonine-linked mannose-containing short oligosaccharide chains in addition to the long-chain rhamnomannans.