title: Capsule of Cryptococcus neoformans grows by enlargement of polysaccharide molecules.
abstract: 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.
authors.affiliation: Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461, USA.
authors.forename: Susana
authors.initials: S
authors.lastname: Frases
authors.forename: Bruno
authors.initials: B
authors.lastname: Pontes
authors.forename: Leonardo
authors.initials: L
authors.lastname: Nimrichter
authors.forename: Nathan B
authors.initials: NB
authors.lastname: Viana
authors.forename: Marcio L
authors.initials: ML
authors.lastname: Rodrigues
authors.forename: Arturo
authors.initials: A
authors.lastname: Casadevall
mesh_terms: D003455:Cryptococcus neoformans / Q000737:chemistry* / Q000166:cytology / Q000254:growth & development*; D008863:Microspheres; D008954:Models, Biological; D010316:Particle Size; D011134:Polysaccharides / Q000737:chemistry*
chemical_list: D011134:Polysaccharides