Abstract

Cryptococcus neoformans reported as life-threatening fungus has many factors for virulence. By virtue of its melanin production, two strains (FBC1and NBM3) from clinical and environmental sources respectively, were selected for mutation. Sodium azide as metabolite that can penetrate and interact with DNA was selected as a mutagen. After the application of this mutagen at different concentrations (0.3-1.0 mg/ml) on C. neoformans, this resulted in the formation of auxotrophic mutants that were unable to grow on minimal medium. The concentration at which these auxotrophic mutants were created was 0.3 mg/ml sodium azide. However the growth of these mutants on complete medium expressed different phenotypic responses to fluconazole as compared to the wild type. Interestingly, this difference did not reflect when tested for melanin production. Thus, this led to the suggestion that melanin involvement in the virulence of C. neoformans may not be critical. Taking together, development of auxotrophic mutants is seen as tools for genetic studies and virulence analysis. 

Keywords: auxotrophic mutant, mutagen, DNA, melanin and virulence