title: Morphologica and structural changes during the yeast-to mold conversion of Phialophora dermatitidis.
abstract: The details of the morphological and structural events occurring during yeast-to-mold conversion of the human pathogenic fungus Phialophora dermatitidis as seen by phase-contrast microscopy and electron microscopy are described and illustrated. Budding yeasts growing exponentially were observed to have thin walls and a cytoplasm exhibiting the characteristics of rapidly growing cells including numerous mitochondria, abundant ribosomes, few vacuoles, and little accumulation of storage material. In contrast, thick-walled yeasts were characterized by less apparent or significantly fewer mitochondria and ribosomes and the presence of considerable amounts of storage materials. Microscope observations of yeast-to-mold conversion revealed that only thick-walled yeasts having prominent lipid bodies in their cytoplasm converted to hyphal forms. Typically, the thick-walled yeast formed two to a number of moniliform hyphal cells which in turn often produced true hyphae. The results indicated that yeasts of P. dermatitidis must acquire spore-like characteristics by becoming thick-walled and by accumulating considerable endogenous substrate reserves before they convert and produce hyphae.
mesh_terms: D002473:Cell Wall; D003470:Culture Media; D003593:Cytoplasm; D002479:Inclusion Bodies; D007700:Kinetics; D008055:Lipids / Q000302:isolation & purification; D008854:Microscopy, Electron; D008858:Microscopy, Phase-Contrast; D008928:Mitochondria; D010676:Phialophora / Q000166:cytology* / Q000254:growth & development; D011110:Polymorphism, Genetic; D012270:Ribosomes; D013194:Staining and Labeling
chemical_list: D003470:Culture Media; D008055:Lipids