The morphology of Cryptococcus neoformans in human cryptococcosis a light-, phase-contrast and electron-microscopic study

The structural unit of melanin in the cell wall of the fungal pathogen Cryptococcus neoformans

“…Finally, ongoing aggregation of melanin granules within the cell wall is supported by eumelanin biomimetic studies demonstrating that consolidation of type-B particles is due to high amounts of the laccase enzyme (46), which is in agreement with increased laccase localization at the outer edge of the cell wall versus the inner edge (88). Melanin-layered deposition on the cell wall follows the existence of membranous sheets described in early ultrastructural studies of the cryptococcal cell wall (93,94) (Fig. 12F); however, as we have demonstrated in this study, melanin particles are loosely associated with an acid-labile polysaccharide matrix that makes this layout within the melanized cell wall difficult to demonstrate.…”

“…Finger-like protrusions of the plasma membrane scoop up melanosomes to transport them from the cytosol to the cell wall (C and D, white arrowheads). Once in the cell wall, aggregation of melanosomes up to 200-nm melanin granules might be promoted by laccase enzyme delivered to the cell wall via MVB fusion with the plasma membrane (46, 81, 89) (E), whereas their arrangement within the fungal cell wall may use as a scaffold concentric membranous sheets reported in basidiomycetes(49,93,94) (F, white arrows). Melanosomes anchor to the cell wall via multiple interactions: (i) associative and covalent interactions between them and cell-wall constituents (chitin, chitosan, glucans, and lipids), possibly mediated by Blp1-chitin and CNAG_05312glucans/chitin/chitosan(16,18,19), and (ii) electrostatic interactions modulated by chitosan-melanin charges(14,31,32,34).…”

Humoral response againstCryptococcus neoformansmannoprotein antigens in HIV-infected patients

“…MPs are glycoproteins of the cell envelope of C. neoformans in which the polysaccharidic moiety is mainly represented by polymers of mannose. MPs have not only been purified from capsular material but also from cell wall preparations obtained by mechanical destruction of the cells [11–16]. MPs, like the other capsular components, are also secreted into the extracellular environment.…”

Oral cryptococcosis: case report of salivary gland involvement in an AIDS patient

“…Therefore, especially when small and not abundant, they are not easily seen in tissue sections (S. 21). The capsule is mucopolysaccharide in nature (22) and stains well with Mayer's mucicarmine and Alcian blue. The stained capsule may have a scalloped appearance as the result of irregular contraction during fixation.…”