UV irradiation induced high frequency of colonial variants with altered morphology in Sporothrix schenckii

Ultraviolet light (UV) exposure of Sporothrix schenckii strains resulted in a high frequency of morphological variants that ranged from 10(-3) to 10(-1) depending on the strain and dose of UV. Based on their morphological differences, these variants were classified into five different groups. One common feature among them was that they were smaller in size compared to the wild type. Two morphological phenotypes (II and IV) were fuzzy, like the wild-type colony, and only the colony size was altered. Phenotypes I, III and V had different shapes; they lost the fuzzy appearance and the individual hyphae in the colony were of aberrant shape. Stable and non-stable morphological variants were found in the population; reversion of the mutant phenotype was always to the wild-type phenotype. Unlike Candida albicans, phenotypic switching was not found in individual colonial phenotypes.