Mycelial phase of Paracoccidioides brasiliensis and Blastomyces dermatitidis: an electron microscope study.

A comparative study of the mycelial phase of Paracoccidioides brasiliensis and Blastomyces dermatitidis reveals that both fungi are very much alike, containing multiple nuclei and nuclear pores, mitochondria, ribosomes, scarce endoplasmic reticulum, intracytoplasmic membrane systems, glycogen, and vacuoles. Shadowed cell walls show fine fibrillar surfaces that contrast with those in the yeast phase. The intracytoplasmic membrane system is continuous with the plasma membrane and is similar to bacterial mesosomes. Granules with light cores and dark rims are observed in the plasma membrane. Live hyphae growing inside a dead hypha are found much more frequently in immersed cultures than in solid-medium cultures, suggesting that breakage of the hypha could elicit this phenomenon.