Journal of General Microbiology (1991), 137, 837-844. Printed in Great Britain 837 Characterization of Fonsecaea pedrosoi melanin CELUTA S. ALVIANO,'* SONIA R. FARBIARZ,~ WANDERLEY DE SOUZA,~ JAYME ANGLUSTER' and LUIZ R. TRAVASSOS3 Instituto de Microbiologia and Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Ilha do Fundiio, 21941, Rio de Janeiro, Brazil 3Disciplinade Micologia, Escola Paulista de Medicina, Siio Paulo, SP 04023, Brazil (Received 27 June 1990; revised 21 November 1990; accepted 28 November 1990) The constituents of the melanin complex from mycelial forms of Fonsecaea pedrosoi were partially characterized. The pigment was mainly accumulated on large alkali-extractable, electron-dense cytoplasmic bodies (melanosomes)and, apparently, on the outer layer of the cell wall as external deposits within verrucose outgrowths. Using electron microscopy and Thiky's periodate/thiosemicarbazide/silver proteinate staining method, glycogen- like particles were also detected at the periphery of the cells. Melanin constituents comprised aromatic and aliphatic/glycosidic structures with a predominance of the latter. Infrared spectra showed the presence of hydroxyl, carbonyl and carboxyl groups. The aliphatic/glycosidic moiety consisted of fatty acids and polysaccharides with protein, in a ratio protein/polysaccharide 1 : 15. Rhamnose, mannose, galactose and glucose (in the ratio 1 : 2: 4: 3.5) were the constituents of the polysaccharide. Lipid components included even-numbered, saturated and unsaturated fatty acids (in the ratio 2: 1) ranging from C16 to Cis. Palmitic and oleic acids were the prominent fatty acids. Aspartic and glutamic acids, leucine, glycine and alanine were the major amino acids. Non- pigmented cells of F.pedrosoi were studied for comparison with the pigmented forms: they did not accumulate acid- insoluble precursors of melanin. Introduction Fonsecaea pedrosoi is one of the agents of chromoblasto- mycosis, a chronic infection characterized by dry, crusted, warty, violaceous lesions that spread locally but are usually limited to the skin and subcutaneous tissue. Tissue forms of the fungus comprise hyphal segments and brown, thick-walled sclerotic bodies. Cultured forms grown in a synthetic medium for prolonged periods at 28 "C are mainly filamentous (Butterfield & Yong, 1976). Dematiaceous fungi pathogenic to humans usually form dark polymeric pigments, generally referred to as melanins, which are deposited on the fungal cell wall (Ellis & Griffiths, 1974; Ellis, 1976). It has been suggested that in these pathogens the pentaketide biosynthetic pathway is the predominant mechanism for cell wall melanization (Taylor et al., 1987). In many cases, however, pigment biosynthesis may involve the Abbreviations : CD, Czapeck-Dox (medium); SDA, Sabouraud dextrose agar; TFA, trifluoroacetic acid. phenol oxidase enzyme system. The physiological roles of fungal melanins are still under investigation (Cole, 1986). Melanins may influence the storage of water and ions (White, 1958), and render micro-organisms resistant to lysis (Bull, 1970) and solar radiation (Sussman, 1968). Inhibition of the pentaketide pathway of melanin synthesis in Wangiella dermatitidis may decrease the pathogenicity of this fungus (Geis et al., 1984). There have been few studies on the surface structures of dark-pigmented F. pedrosoi, but we have reported the presence of sialylated constituents on the external layers of the cell wall in both the hyphae and the conidia of this fungus (Souza et al., 1986). Both sialyl residues and melanin may play an important role in the pathogenicity of this fungus and of other dark-pigmented fungi which cause disease in plants and animals (Cole, 1986; Travassos, 1985). The purpose of this investigation was to study the localization and chemical structure of the melanin complex from mycelial forms of F. pedrosoi grown in a synthetic medium. 0001-6332 O 1991 SGM