MELANIN-DEFICIENT MUTANTS OF CRYPTOCOCCUS-NEOFORMANS

Cryptococcus neoformans is a significant fungal pathogen in immunocomp romised patients. The ability of C. neoformans to produce melanin has been correlated with virulence. The role of melanin in promoting virul ence is unclear, although an anti-oxidant function has been suggested. To begin to define the genetic mechanisms responsible for melanin pro duction in C neoformans, we describe the isolation of seven melanin-de ficient mutant classes. Some of the mutants can be suppressed by addit ion of Cu2+ to media, suggesting that the phenoloxidase of C neoforman s, like other fungal phenoloxidases, contains copper. Other mutants di splay a recessive sterile phenotype. A genetic and phenotypic characte risation of these mutants is presented.