The elastic properties of the Cryptococcus neoformans capsule

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

Research output: Contribution to journalArticlepeer-review

Abstract

Microbial capsules are important for virulence, but their architecture and physical properties are poorly understood. The human pathogenic fungus Cryptococcus neoformans has a large polysaccharide capsule that is necessary for virulence and is the target of protective antibody responses. To study the C. neoformans capsule we developed what we believe is a new approach whereby we probed the capsular elastic properties by applying forces using polystyrene beads manipulated with optical tweezers. This method allowed us to determine the Young's modulus for the capsule in various conditions that affect capsule growth. The results indicate that the Young's modulus of the capsule decreases with its size and increases with the Ca2+ concentration in solution. Also, capsular polysaccharide manifests an unexpected affinity for polystyrene beads, a property that may function in attachment to host cells and environmental structures. Bead probing with optical tweezers provides a new, nondestructive method that may have wide applicability for studying the effects of growth conditions, immune components, and drugs on capsular properties.

Original languageEnglish (US)
Pages (from-to)937-945
Number of pages9
JournalBiophysical journal
Volume97
Issue number4
DOIs
StatePublished - Aug 19 2009
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics

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