Comparative Study of the Cell Walls of the Yeastlike and Mycelial Phases of Histoplasma capsulatum

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Cell walls were prepared from the yeastlike and mycelial phases (YP and MP) of Histoplasma capsulatum and from Saccharomyces cerevisiae by mechanical disruption and washing. Lipids were extracted with methanol-ether, chloroform, and acidified methanol:ether; a final extraction was made with ethylenediamine. The lipid contents of H. capsulatum YP and MP walls were about the same. Qualitative and quantitative analyses were made of the products obtained from treatment of the cell walls, or fractions from them, with weak acid or with enzymatic preparations containing glucanase and chitinase activities. YP walls contained much larger quantities of chitin and smaller quantities of mannose and amino acids than the MP walls. H. capsulatum MP was shown to resemble S. cerevisiae by low chitin content and by the presence of a mannose polymer, soluble in ethylenediamine and water. H. capsulatum MP chitin appeared to be intimately associated with glucose in the wall, since enzymatic hydrolysis of the residue after mild acid hydrolysis of cell walls or fractions from them resulted in the release of glucose and acetylglucosamine; only acetylglucosamine was released from YP walls with such treatment. By electron microscopic observations, the unextracted MP cell walls were much thinner than the YP, and neither wall appeared laminated.

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