Distribution of anionic groups at the cell surface of different Sporothrix schenckii cell types

The distribution of anionic groups at the cell surface of yeastlike forms, hyphae, and conidia of Sporothrix schenckii was studied by staining with colloidal iron hydroxide and cationized ferritin. By using colloidal iron hydroxide it was shown that the external cell wall layer of one strain (strain 1099.18) could be resolved into two reactive sublayers and that these layers were present in many but not all cells of the same population. In contrast, most cells of another strain (strain 1099.12) were stained by colloidal iron hydroxide, but only one reactive layer was seen. Acidic layers of the yeastlike forms of the two strains were much thicker than those of conidia and hyphae. By the cationized ferritin staining procedure it was observed that the acidic layers of yeast forms sloughed off of cells, probably due to cell-cell or cell-medium attrition in shaken submerged cultures or to a process by which the outer layers detach from cells as they are replaced by newly synthesized ones. The colloidal iron hydroxide- and cationized ferritin-reactive cell surface layers of S. schenckii correspond to the previously described (L. R. Travassos et al., Exp. Mycol. 1:293-305, 1977) concanavalin A-reactive peptidorhamnomannan complexes, and their reactivity is probably due to the presence of acidic amino acids of low pK values rather than to glucuronic acid units.