Melanin-deficient mutants of Cryptococcus neoformans.

Cryptococcus neoformans is a significant fungal pathogen in immunocompromised patients. The ability of C. neoformans to produce melanin has been correlated with virulence. The role of melanin in promoting virulence is unclear, although an anti-oxidant function has been suggested. To begin to define the genetic mechanisms responsible for melanin production in C. neoformans, we describe the isolation of seven melanin-deficient mutant classes. Some of the mutants can be suppressed by addition of Cu2+ to media, suggesting that the phenoloxidase of C. neoformans, like other fungal phenoloxidases, contains copper. Other mutants display a recessive sterile phenotype. A genetic and phenotypic characterisation of these mutants is presented.