Chemical and ultrastructural studies on the cell walls of the yeastlike and mycelial forms of Histoplasma farciminosum.

The cell wall of the yeast form of Histoplasma farciminosum contains 13.2% beta-1,3-glucan, 1.0% galactomannan, and 25.8% chitin, whereas the cell wall of mycelial form has 21.8, 4.5, and 40%, respectively, for the same polymers. Also, the cell wall of the yeast form contains alpha-1,3-glucan (13.5%) and an unidentified polymer (21.5%). Chitin, one of the structural polymers of both yeast and mycelial cell walls, is identified as thin isolated fibers (4 nm wide) or in thick bundles (50 nm wide) of fibers. beta-(1-3)-Glucan is also found as thin isolated fibers indistinguishable from isolated fibers of chitin. Fibers 14 nm wide and resembling alpha-(1-3)-glucan fibers of other fungi are found in the yeast form. The results reported here do not give support to the proposal for a different taxonomic classification.