GENETIC-STUDY OF OXYGEN RESISTANCE AND MELANIZATION IN CRYPTOCOCCUS-NEOFORMANS

Genetic analysis of oxygen-sensitive mutants of Cryptococcus neoforman s revealed two loci (oxy1 and oxy2) linking hyperoxia sensitivity to p roduction of melanin, a known virulence factor. Hyperoxia-sensitive st rain 562 (oxy1 oxy2) is albino and avirulent. oxy2-defective strains l acking the oxy1 defect are melanin deficient but show normal hyperoxia resistance. Mutants defective at three additional mapped melanin loci fail to show hyperoxia sensitivity in the oxy1 background. Revertants of strain 562, which regain the ability to synthesize melanin by muta tion at suppressor sites unlinked to oxy2, retain the oxygen sensitivi ty conferred by their oxy1 and oxy2 defects. These data identify the m elanin gene oxy2 as unique in its association of hyperoxia resistance and melanization.