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Published on: February 14, 2011
Conversion in strains of Histoplasma capsulatum
Abstract:
Pine, Leo (Duke University, Durham, N. C.) and Robert E. Webster. Conversion in strains of Histoplasma capsulatum. J. Bacteriol. 83:149-157. 1962-Photographs of mycelial elements taken at various time intervals from a single strain of Histoplasma capsulatum have shown the direct conversion of microconidia to yeast cells by polar and nonpolar budding, the formation of yeast cells by budding of hyphal cells, and the probable conversion of hyphal cells to yeast phase by monilial chain formation. In addition, studies of fixed-slide preparations of a second strain have indicated the formation of stalked yeast cells arising in a manner similar to that observed for microconidia formation but, apparently, by-passing the microconidial stage. These observations are discussed briefly in regard to temperature-induced changes in cell-wall synthesis during conversion.
Insights
This study observed Histoplasma capsulatum converting directly from mold to yeast forms through budding. Temperature-induced changes in cell-wall synthesis likely influence this critical dimorphic transition.
Area of Science:
- Medical Mycology
- Microbial Pathogenesis
- Cell Biology
Background:
- Histoplasma capsulatum is a fungus exhibiting dimorphism, existing as mold in the environment and yeast in vivo.
- Understanding the conversion process is crucial for diagnosing and treating histoplasmosis.
Purpose of the Study:
- To investigate the morphological changes during the conversion of Histoplasma capsulatum from mycelial to yeast form.
- To elucidate the mechanisms underlying this dimorphic transition.
Main Methods:
- Time-lapse photography of mycelial elements from a Histoplasma capsulatum strain.
- Microscopic examination of fixed-slide preparations from a second strain.
Main Results:
- Direct conversion of microconidia to yeast cells via budding was observed.
- Yeast cells also formed through budding of hyphal cells and potential monilial chain formation.
- A second strain showed stalked yeast cell formation, bypassing the microconidial stage.
Conclusions:
- Morphological evidence supports direct conversion pathways in Histoplasma capsulatum.
- Temperature-induced alterations in cell-wall synthesis are implicated in the dimorphic transition.
