FIG. 4.

Influence of divalent ions on capsule expression. (A) Treatment of dead yeast cells with EDTA resulted in a significantly reduced capsule size. (B) Increasing concentrations of Ca²⁺ initially induce an enhancement in capsule expression, but excess cation concentrations cause a decrease in capsule size. (C) Images of the most-representative capsule size-related events shown in panel B are depicted, with emphasis on the very large capsules observed after fungal cultivation in the presence of 0.03 mM CaCl₂. (D) The incubation of dead, poorly encapsulated C. neoformans cells with GXM in the presence of various Ca²⁺ concentrations results in polysaccharide incorporation, as determined by capture ELISA (4).