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Aspects of the dimorphism of Histoplasma farciminosum: a light and electron microscopic study
Abstract:
Within 48h following the induction of mycelial to yeast-like phase conversion of Histoplasma farcininosum, randomly occurring hyphal cells were observed to contain multiple nuclei and markedly increased numbers of mitochondria. Yeast-like cells arose as buds from swollen tips of terminal hyphae, as sessile buds along the hyphae, and as buds from chlamydospores. Yeast-like cells were characterized by the presence of numerous buds over the surface of the mother cell. Bud scars were evident in the cell wall of the mother cell following abscission of the bud cell. Little similarity was noted between the fine structure of yeast-like H. farciminosum and that reported for H. capsulatum. The yeast-like cells of H. frciminosum underwent rapid transformation to the mycelial phase at 25 degrees C. The hyphal cell wall originated from the inner layer of cell wall of the yeast-like form. The cytoplasm of the hyphal cell usually contained a single nucleus, scattered mitochondria and occasional lipid storage bodies. Occasionally, Woronin bodies were observed at the septal pore.
Insights
Histoplasma farcininosum rapidly converts between mycelial and yeast-like phases. This study details the distinct cellular structures and transformations during this dimorphic transition, offering insights into fungal morphology.
Area of Science:
- Mycology
- Cell Biology
- Fungal Pathogenesis
Background:
- Histoplasma farcininosum exhibits dimorphism, switching between mycelial and yeast-like forms.
- Understanding this transition is crucial for studying fungal biology and host-pathogen interactions.
Purpose of the Study:
- To investigate the ultrastructural changes during the mycelial to yeast-like phase conversion of Histoplasma farcininosum.
- To compare the fine structure of yeast-like H. farcininosum with Histoplasma capsulatum.
Main Methods:
- Induction of phase conversion in Histoplasma farcininosum.
- Transmission electron microscopy to observe cellular ultrastructure.
- Comparative analysis of yeast-like and mycelial forms.
Main Results:
- Hyphal cells showed increased nuclei and mitochondria before yeast-like budding.
- Yeast-like cells budded from hyphae and chlamydospores, displaying multiple buds and bud scars.
- Significant ultrastructural differences were observed between yeast-like H. farcininosum and H. capsulatum.
- Yeast-like cells rapidly reverted to the mycelial phase at 25°C, with the hyphal cell wall forming from the yeast cell wall's inner layer.
Conclusions:
- Histoplasma farcininosum undergoes a distinct dimorphic transition with unique ultrastructural characteristics.
- The observed differences suggest variations in cellular mechanisms between Histoplasma species.
- The study provides a detailed morphological description of H. farcininosum's phase conversion.