The effect of growth media upon the ultrastructure of Blastomyces dermatitidis.

The ultrastructure of yeast, intermediate transitional forms, and mycelia of Blastomyces dermatitidis cultured in brain heart infusion (BHI) was compared with that of like forms grown in leucine-glucose (LG) medium. Blastomyces dermatitidis yeasts were also grown in yeast extract - peptone (YP) medium and in glucose - yeast extract - peptone (GYP) medium, and their ultrastructures were compared with BHI-grown yeasts. Yeast, intermediate, and mycelial cells cultured in LG had more granular cytoplasm and better defined membranes than analogous BHI-grown cells. Yeasts grown in LG contained more glycogen and fewer lipid bodies and had no visible intracytoplasmic membrane systems. Some yeasts from LG cultures had bizarre shapes and structure. Intermediate and mycelial forms from LG cultures contained more glycogen and lipid bodies than analogous cells from BHI. Yeasts grown in YP had a more highly defined internal structure than BHI-grown yeasts. Some cells were doubly budded. and some were elongated. Similar elongated yeasts were found growing in GYP. Yeasts grown in GYP lacked a well-defined internal structure and had less glycogen than BHI-grown yeasts. They had no visible lipid bodies, but large vacuoles were present. Intrayeast hyphae were observed only in BHI-grown intermediate cells.