Are giant cells conidia in Sporothrix schenckii? -Freeze-fracture electron microscopic observation-

Area of Science:

• Mycology
• Cell Biology
• Pathogenic Fungi

Background:

• Sporothrix schenckii is a pathogenic dimorphic fungus.
• Giant cells are observed in S. schenckii cultures, particularly on Sabouraud's dextrose agar.
• Understanding the nature of these giant cells is crucial for comprehending fungal morphology and adaptation.

Purpose of the Study:

• To investigate the plasma membrane ultrastructure of S. schenckii giant cells.
• To determine culture conditions that promote giant cell formation.
• To identify the origin and potential function of giant cells in S. schenckii.

Main Methods:

• Culturing S. schenckii at different temperatures (27°C and 37°C) and durations (1-8 weeks) on brain heart infusion and Sabouraud's dextrose agar.
• Quantifying conidia, hyphae, and giant cells (brownish and non-brownish) using light microscopy.
• Analyzing plasma membrane ultrastructure of giant cells using freeze-fracture electron microscopy.

Main Results:

• Brownish giant cells were more prevalent in cultures maintained for extended periods.
• Freeze-fracture electron microscopy revealed plasma membrane characteristics in giant cells similar to mature conidia.
• Giant cells exhibit trench-like invaginations, a feature of S. schenckii conidia.

Conclusions:

• Giant cells in S. schenckii cultures are likely conidia.
• Their increased prevalence under prolonged cultivation suggests they may represent starved or dormant forms.
• The study provides insights into the morphological plasticity and survival strategies of pathogenic fungi.