Capsule of Cryptococcus neoformans grows by enlargement of polysaccharide molecules

Susana Frases, Bruno Pontes, Leonardo Nimrichter, Nathan B. Viana, Marcio L. Rodrigues, Arturo Casadevall

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65 Scopus citations


The human pathogenic fungus Cryptococcus neoformans has a distinctive polysaccharide (PS) capsule that enlarges during infection. The capsule is essential for virulence, but the mechanism for capsular growth is unknown. In the present study, we used dynamic light scattering (LS) analysis of capsular PS and optical tweezers (OT) to explore the architecture of the capsule. Analysis of capsular PS from cells with small and large capsules by dynamic LS revealed a linear correlation between PS effective diameter and microscopic capsular diameter. This result implied that capsule growth was achieved by the addition of molecules with larger effective diameter, such that some molecules can span the entire diameter of the capsule. Measurement of polystyrene bead penetration of C. neoformans capsules by using OT techniques revealed that the outer regions were penetrable, but not the inner regions. Our results provide a mechanism for capsular enlargement based on the axial lengthening of PS molecules and suggest a model for the architecture of a eukaryotic microbial capsule.

Original languageEnglish (US)
Pages (from-to)1228-1233
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number4
StatePublished - Jan 27 2009
Externally publishedYes


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