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Updated: Feb 3, 2026
08:24
Size Matters: Measurement of Capsule Diameter in Cryptococcus neoformans
Published on: February 27, 2018
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The Capsule of Cryptococcus neoformans Modulates Phagosomal pH through Its Acid-Base Properties
Carlos M De Leon-Rodriguez1, Man Shun Fu1, M Osman Çorbali1
1Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
Msphere
|October 26, 2018
Summary
The capsule of Cryptococcus neoformans, rich in glucuronic acid, acts as a buffer, preventing phagosomal acidification. This mechanism aids fungal survival within macrophages, contributing to virulence.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Phagosomal acidification is crucial for eliminating ingested microbes by phagocytic cells.
- Pathogenic microbes often evade this process by interfering with phagosome maturation.
- Cryptococcus neoformans thrives in acidic phagosomes, benefiting from the environment for replication.
Purpose of the Study:
- To investigate the role of glucuronic acid residues in the Cryptococcus neoformans capsule in modulating phagosomal acidity.
- To determine if the cryptococcal capsule influences the phagosomal environment's pH.
Main Methods:
- Ratiometric fluorescence imaging of phagosomes containing encapsulated or nonencapsulated C. neoformans and control beads.
- Acid-base titration of isolated C. neoformans capsular polysaccharide.
Main Results:
- Phagosomes containing beads were significantly more acidic than those with C. neoformans.
- Phagosomes with nonencapsulated C. neoformans were more acidic than those with encapsulated cells.
- C. neoformans polysaccharide exhibited weak acid properties with buffering capacity around pH 4-5.
Conclusions:
- The glucuronic acid in the C. neoformans capsule buffers phagosomal acidification.
- Capsular interference with phagosomal acidity is a novel virulence mechanism for C. neoformans.
- The acid-base properties of microbial capsules are important in host-microbe interactions.
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