The readily extracted lipids of Histoplasma capsulatum and Blastomyces dermatitidis

Abstract

1. 1. Cell walls and cell sap (lyophilized preparation of whole cell minus cell wall) of both yeast and mycelial phases of Histoplasma capsulatum and Blastomyces dermatitidis were extracted with chloroform-methanol and the lipids thus derived were compared. 2. 2. There was little difference between the total readily extracted lipid of the cell sap preparations of yeast and mycelial phases of H. capsulatum. Cell saps of B. dermatitidis generally contained less lipid than H. capsulatum; the mycelial phase contained about half that of the corresponding yeast phase preparations. Most cell walls had less than 3% lipid, with less m mycelial phase than corresponding yeast phase walls. 3. 3. Cell wall and cell sap extracts regardless of source contained phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, triglycerides, diglycerides, sterols, sterol esters and free fatty acids. Triglycerides were the greatest single component in the extracts; phosphatidyl choline and phosphatidyl ethanolamine were the most concentrated phospholipids. Quantitative densitometry of these three classes of compounds revealed little difference between cell wall and cell sap preparations, or yeast and mycelial phase preparations, that could not be explained on the basis of incubation time or different rates of metabolism in different media. 4. 4. The major differences between cell walls and homologous cell sap, and yeast phase and mycelial phase, involved primarily the quantities of oleic and linoleic acids in the extracts. These two fatty acids together, however, accounted for 75–80% of the total fatty acids of all extracts; the relative proportions of the two distinguished the preparations. In general, oleic acid predominated in yeast phase extracts; linoleic acid was either equal or greater in concentration in the mycelial phase extracts. Cell walls usually contained more oleic acid and less linoleic acid than homologous cell saps. This was particularly obvious when the fatty acids of the lipid classes were examined. Even though differences were demonstrated between cell wall and cell sap preparations, and yeast and mycelial phase preparations, little difference could be demonstrated between analogous lipid extracts of H. capsulatum and B. dennatitidis.