Differences in the cell wall architecture of melanin lacking and melanin producing Cryptococcus neoformans clinical isolates from India: An electron microscopic study

Cryptococcus neoformans is an important opportunistic fungal pathogen that causes life-threatening infection of the central nervous system. A major virulence factor for C. neoformans is the production of melanin in the cell wall. Using transmission electron microscopy, we studied the cell walls of three pairs of isolates obtained from patients with dual cryptococcal infections, where a melanotic and an albino strain were isolated from the CSF of each patient. Transmission Electron Microscopy revealed that the albino strains lacked a melanin layer whereas a melanin layer was associated with the cell wall of the melanotic strains, comprising approximately 75% of the cell wall area. The cell wall size of the melanin producing cells was approximately double the size the albino isolates' cell walls (p value ≤ 0.003). In this study TEM revealed that the differences in the ultrastructure of the melanin lacking and melanin producing isolates were associated to the cell wall and the melanin layer.