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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.
Insights
Phialophora dermatitidis yeast cells convert to mold only after developing thick walls and accumulating storage reserves. This transformation involves morphological and structural changes essential for hyphal development in this human pathogen.
Area of Science:
- Medical Mycology
- Cell Biology
- Fungal Pathogenesis
Background:
- Phialophora dermatitidis is a human pathogenic fungus.
- Understanding its morphological transitions is crucial for controlling infections.
Purpose of the Study:
- To detail the morphological and structural changes during the yeast-to-mold conversion of Phialophora dermatitidis.
- To identify the cellular characteristics enabling this fungal dimorphism.
Main Methods:
- Phase-contrast microscopy was used to observe cellular dynamics.
- Electron microscopy provided detailed structural insights.
- Exponentially growing and thick-walled yeast forms were analyzed.
Main Results:
- Rapidly growing yeasts have thin walls, abundant mitochondria and ribosomes, and few vacuoles.
- Thick-walled yeasts show reduced mitochondria/ribosomes and accumulate storage materials, notably lipid bodies.
- Only thick-walled yeasts with prominent lipid bodies converted to hyphal forms, initially as moniliform cells.
Conclusions:
- Yeast-to-mold conversion in P. dermatitidis requires yeasts to develop spore-like characteristics.
- Acquisition of thick walls and significant storage reserves (endogenous substrate) are prerequisites for hyphal formation.