The polysaccharide capsule of the pathogenic fungus Cryptococcus neoformans enlarges by distal growth and is rearranged during budding

作者：Óscar Zaragoza, Andrew Telzak, Ruth A. Bryan, Ekaterina Dadachova, Arturo Casadevall · 发表于：Molecular Microbiology · 年份：2005 · DOI：10.1111/j.1365-2958.2005.04928.x · 被引用次数：92 · 研究领域：Fungal Infections and Studies、Antifungal resistance and susceptibility、Plant Disease Resistance and Genetics

The capsule of Cryptococcus neoformans can undergo dramatic enlargement, a phenomenon associated with virulence. A prior study that used Ab to the capsule as a marker for older capsular material concluded that capsule growth involved the intermixing of new and old capsular material with displacement of older capsular polysaccharide towards the surface. Here we have revisited that question using complement (C), which binds to capsular polysaccharide covalently, and cannot redistribute by dissociation and binding at different sites. The experimental approach involved binding of C to cells with small capsules, inducing capsule growth, and following the location of C relative to the cell wall as the capsule enlarged. C remained close to the cell wall during capsule growth, indicating that capsule enlargement occurred by addition of new polysaccharide near the capsule edge. This conclusion was confirmed by an independent method that employed radioactive metabolic labelling of newly synthesized capsule with 3H-mannose followed by gradual capsular stripping with gamma-radiation. Capsule growth proceeded to a certain size, which was a function of cell size, and was not degraded when the cells were transferred to a non-inducing medium. During budding, an opening appeared in the capsule of the mother cell that permitted the nascent bud to separate. Scanning EM suggested that a physical separation formed between the capsules of the mother and daughter cells during budding, which may avo...