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Molecular architecture of the Cryptococcus neoformans capsule
Marcellene A Gates1, Peter Thorkildson, Thomas R Kozel
1Department of Microbiology and Immunology/320, University of Nevada School of Medicine, Reno, NV 89557, USA.
Molecular Microbiology
|March 31, 2004
Summary
The Cryptococcus neoformans capsule has variable porosity, with a dense interior and a porous, plastic edge that interacts with immune cells. This structure influences how serum proteins bind to the yeast.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Many pathogenic microbes possess capsules that inhibit phagocytosis.
- The large polysaccharide capsule of Cryptococcus neoformans offers a unique model to study capsular structure and function.
Purpose of the Study:
- To investigate the molecular architecture of the Cryptococcus neoformans capsule.
- To understand the relationship between capsular structure and interaction with serum proteins.
Main Methods:
- Assessing macromolecule permeability based on Stokes radii.
- Measuring antibody fragment (Fab) binding to determine matrix density.
- Chemical deconstruction using dimethyl sulfoxide (DMSO).
- Evaluating capsule plasticity.
Main Results:
- The capsule exhibits variable porosity, increasing with distance from the cell wall.
- High internal density restricts macromolecule penetration near the cell wall.
- The capsular edge is less dense, more plastic, and permeable.
- In vivo yeast capsules (from infected tissue) show higher matrix density than in vitro grown capsules.
Conclusions:
- The Cryptococcus neoformans capsule is a dynamic matrix with distinct inner and outer regions.
- Capsular architecture directly impacts interactions with host immune components.
- In vivo conditions induce a denser capsule compared to in vitro growth.