Evaluation of melanin production by Sporothrix luriei

Abstract

There is a paucity of studies on the cell biology of Sporothrix luriei, the less common of the pathogenic Sporothrix species worldwide. The production of DHN-melanin, eumelanin, and pyomelanin were evaluated on the mycelial and yeast forms of the S. luriei ATCC 18616 strain. The mycelial form of this species produced only pyomelanin, which protected the fungus against environmental stressors such as ultraviolet light, heat, and cold. The yeast form was unable to produce any of the tested melanin types. The lack of melanin in the parasitic form of S. luriei may be an explanation for its low frequency in human infections.

Fig. 1. evaluation of melanin production by Sporothrix luriei. (A): macroscopic aspects of hot-acid resistant particles yielded by mycelial (M) and yeast (Y) cells grown in minimal medium and minimal medium supplemented with 1 mM L-DOPA; (B): microscopic aspects of the hot-acid resistant particles, bar: 10 µm; (C): black-soluble pigment observed in the supernatant of the mycelial (M) culture in minimal medium supplemented with 10 mM L-tyrosine and absence of the pigment in the culture supernatant of the yeast culture in the same medium.

Fig. 2. resistance of melanised Sporothrix luriei conidia against environmental stressors. (A) growth (CFU/mL; mean ± standard deviation) of cultures with and without pyomelanin after ultraviolet light irradiation for different exposure times; (B) percent survival (mean ± standard deviation) of conidia with and without pyomelanin after heat (38°C) and cold (4°C) exposures. For all conditions, p < 0.05.