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Fungitoxicity of muramidase. Ultrastructural damage to Candida albicans
Abstract:
The antifungal activity of hen egg-white lysozyme was investigated in vitro using a hypotonic medium designed to support an anabolic cellular state with minimal growth stimulation. The pathogenic yeast Candida albicans was found to be sensitive to microgram amounts of hen egg-white lysozyme. This susceptibility was evidenced by sluggish growth and a dose-dependent killing process. Transmitted and scanning electron microscopic observations on lysozyme-treated C. albicans yeast cells revealed the following ultrastructural modifications: (1) plasmolysis, vacuolar expansion and wrinkled surface configuration; (2) unremitting accumulation of wall-like material that bulged into the periplasmic space; (3) qualitative changes in the organization of the wall. Ongoing structural modifications within the wall were highlighted with the cationic heavy metal dye ruthenium red. A disruption in the permeability of the cytoplasmic membrane was evidenced by modification 1 and by differential staining characteristics in light microscopy. The superimposed osmotic imbalance was identified as the cause of cell death. It is proposed that lysozyme acts on C. albicans by two distinct complementary mechanisms: enzymatic hydrolysis of N-glycosidic bonds that link polysaccharides and structural proteins of the wall; injury to the cytoplasmic membrane as a result of a cationic protein kind of interaction.
Insights
Hen egg-white lysozyme exhibits antifungal activity against Candida albicans. This yeast is sensitive to lysozyme, which causes cell wall damage and membrane permeability disruption, leading to cell death.
Area of Science:
- Microbiology
- Biochemistry
- Cell Biology
Background:
- Candida albicans is a pathogenic yeast causing infections.
- Understanding its susceptibility to antimicrobial agents is crucial for developing new treatments.
Purpose of the Study:
- To investigate the in vitro antifungal activity of hen egg-white lysozyme against Candida albicans.
- To elucidate the cellular and ultrastructural mechanisms of lysozyme's action on C. albicans.
Main Methods:
- In vitro antifungal assay using a hypotonic medium.
- Transmission and scanning electron microscopy (TEM and SEM) for ultrastructural analysis.
- Ruthenium red staining to visualize cell wall modifications.
Main Results:
- Candida albicans showed sensitivity to microgram amounts of hen egg-white lysozyme.
- Lysozyme induced plasmolysis, vacuolar expansion, and surface wrinkling.
- Ultrastructural changes included periplasmic material accumulation and altered cell wall organization.
- Disruption of cytoplasmic membrane permeability was observed, leading to osmotic imbalance and cell death.
Conclusions:
- Hen egg-white lysozyme possesses significant antifungal activity against Candida albicans.
- Lysozyme acts through dual mechanisms: enzymatic cell wall hydrolysis and cationic interaction with the cytoplasmic membrane.
- These actions lead to cell death primarily due to osmotic imbalance.