Biosynthesis and Functions of a Melanoid Pigment Produced by Species of the Sporothrix Complex in the Presence of l -Tyrosine

Abstract

Sporothrix schenckii is the etiological agent of sporotrichosis, the main subcutaneous mycosis in Latin America. Melanin is an important virulence factor of S. schenckii, which produces dihydroxynaphthalene melanin (DHN-melanin) in conidia and yeast cells. Additionally, L-dihydroxyphenylalanine (L-DOPA) can be used to enhance melanin production on these structures as well as on hyphae. Some fungi are able to synthesize another type of melanoid pigment, called pyomelanin, as a result of tyrosine catabolism. Since there is no information about tyrosine catabolism in Sporothrix spp., we cultured 73 strains, including representatives of newly described Sporothrix species of medical interest, such as S. brasiliensis, S. schenckii, and S. globosa, in minimal medium with tyrosine. All strains but one were able to produce a melanoid pigment with a negative charge in this culture medium after 9 days of incubation. An S. schenckii DHN-melanin mutant strain also produced pigment in the presence of tyrosine. Further analysis showed that pigment production occurs in both the filamentous and yeast phases, and pigment accumulates in supernatants during stationary-phase growth. Notably, sulcotrione inhibits pigment production. Melanin ghosts of wild-type and DHN mutant strains obtained when the fungus was cultured with tyrosine were similar to melanin ghosts yielded in the absence of the precursor, indicating that this melanin does not polymerize on the fungal cell wall. However, pyomelanin-producing fungal cells were more resistant to nitrogen-derived oxidants and to UV light. In conclusion, at least three species of the Sporothrix complex are able to produce pyomelanin in the presence of tyrosine, and this pigment might be involved in virulence. Melanins are polymers with diverse molecular structures, typically black or dark brown, formed by the oxidative polymerization of phenolic and indolic compounds. They are produced by a broad range of organisms, from bacteria to humans. Several fungi can produce melanins, and the functions of these pigments are related to microbial survival under several unfavorable environmental and host conditions (10, 14). The major melanin type encountered among fungi is 1,8-dihydroxynaphthalene melanin (DHN-melanin), which is synthesized from acetyl coenzyme A via the polyketide pathway. This form of melanin is synthesized by several plant and human fungal pathogens. In addition to DHN-melanin, certain fungi can also produce melanin via dihydroxyphenylalanine (DOPA), in which tyrosinases or laccases hydroxylate tyrosine via DOPA to dopaquinone, which then auto-oxidizes and polymerizes, resulting in a polyphenolic heteropolymer that is black (9). Some fungi produce a soluble melanin from L-tyrosine through p-hydroxyphenylpyruvate and homogentisic acid. This soluble pigment is called pyomelanin, and it is similar to the alkaptomelanin produced by humans. Aspergillus fumigatus, Madurella mycetomatis, and Yarrowia lipolytica are examples of fungi that can produce this type of soluble pigment (4,18,20)...

Pyomelanin production in Penicillium chrysogenum is stimulated by l-tyrosine

“…It is possible that pyomelanin plays a role in survival of the fungus under adverse conditions (Turick et al, 2009). In fungi such as Sporothrix and A. fumigatus, this brown pigment is known to help protect against oxidative stress (Schmaler-Ripcke et al, 2009;Almeida-Paes et al, 2012). In bacteria such as Ps.…”

Increase in virulence ofSporothrix brasiliensisover five years in a patient with chronic disseminated sporotrichosis

“…At present, there is only limited information about the virulence of S. brasiliensis. [14][15][16] The aim of this study is to describe the evolution of increased virulence of sequential Sporothrix isolates from a patient with chronic, destructive disseminated sporotrichosis.…”

Activation of Melanin Synthesis in Alternaria infectoria by Antifungal Drugs

“…After centrifugation, the pigment was recovered from the supernatant and the pellet was extracted again until no more extractable pigment was obtained (32,34). For quantification of pigment from A. infectoria, no more steps of purification were undertaken to avoid pigment loss, and the pigment concentration was measured photometrically in a Spectra Max Plus384 spectrophotometer (Molecular Devices, LLC) at a wavelength of 340 nm (35,36).…”