Effects of disrupting the polyketide synthase gene WdPKS1 in Wangiella [Exophiala] dermatitidis on melanin production and resistance to killing by antifungal compounds, enzymatic degradation, and extremes in temperature

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Date

2006-06-19

Authors

Paolo, William F.
Dadachova, Ekaterina
Mandal, Piyali
Casadevall, Arturo
Szaniszlo, Paul J.
Nosanchuk, Joshua D.

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Journal ISSN

Volume Title

Publisher

BMC Microbiology

Abstract

Background: Wangiella dermatitidis is a human pathogenic fungus that is an etiologic agent of phaeohyphomycosis. W. dermatitidis produces a black pigment that has been identified as a dihydroxynaphthalene melanin and the production of this pigment is associated with its virulence. Cell wall pigmentation in W. dermatitidis depends on the WdPKS1 gene, which encodes a polyketide synthase required for generating the key precursor for dihydroxynaphthalene melanin biosynthesis. -- Results: We analyzed the effects of disrupting WdPKS1 on dihydroxynaphthalene melanin production and resistance to antifungal compounds. Transmission electron microscopy revealed that wdpks1Δ-1 yeast had thinner cell walls that lacked an electron-opaque layer compared to wild-type cells. However, digestion of the wdpks1Δ-1 yeast revealed small black particles that were consistent with a melanin-like compound, because they were acid-resistant, reacted with melanin-binding antibody, and demonstrated a free radical signature by electron spin resonance analysis. Despite lacking the WdPKS1 gene, the mutant yeast were capable of catalyzing the formation of melanin from L-3,4-dihyroxyphenylalanine. The wdpks1Δ-1 cells were significantly more susceptible to killing by voriconazole, amphotericin B, NP-1 [a microbicidal peptide], heat and cold, and lysing enzymes than the heavily melanized parental or complemented strains. -- Conclusion: In summary, W. dermatitidis makes WdPKS-dependent and -independent melanins, and the WdPKS1-dependent deposition of melanin in the cell wall confers protection against antifungal agents and environmental stresses. The biological role of the WdPKS-independent melanin remains unclear.

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William F. Paolo Jr., Arturo Casadevall, and Joshua D. Nosanchuk are with the Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA -- Ekaterina Dadachova, Piyali Mandal, Arturo Casadevall, and Joshua D. Nosanchuk are with the Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA -- Ekaterina Dadachova is with the Department of Nuclear Medicine, Albert Einstein College of Medicine, Bronx, NY, USA -- Piyali Mandal is with the Department of Microbiology, All India Institute of Medical Sciences and Division of Infectious Diseases, New Delhi, India -- Paul J. Szaniszlo is with the Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, TX, USA -- 6 Department of Medicine, New York University Medical Center, NY, USA

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Citation

Paolo, William F., Ekaterina Dadachova, Piyali Mandal, Arturo Casadevall, Paul J. Szaniszlo, and Joshua D. Nosanchuk. “Effects of Disrupting the Polyketide Synthase Gene WdPKS1 in Wangiella [Exophiala] Dermatitidis on Melanin Production and Resistance to Killing by Antifungal Compounds, Enzymatic Degradation, and Extremes in Temperature.” BMC Microbiology 6, no. 1 (June 19, 2006): 55. doi:10.1186/1471-2180-6-55.