Affordable Access

Cryptococcus neoformans Can Utilize the Bacterial Melanin Precursor Homogentisic Acid for Fungal Melanogenesis▿

Authors
  • Susana Frases
  • Angela Salazar
  • Ekaterina Dadachova
  • Arturo Casadevall
Publisher
American Society for Microbiology
Publication Date
Nov 10, 2006
Source
PMC
Keywords
License
Unknown

Abstract

Cryptococcus neoformans melanizes in the environment and in mammalian tissues, but the process of melanization in either venue is mysterious given that this microbe produces melanin only from exogenous substrates. Understanding the process of melanization is important because melanization is believed to protect against various stresses in the environment, including UV radiation, and pigment production is associated with virulence. Melanization in C. neoformans requires the availability of diphenolic precursors. In contrast, many bacteria synthesize melanin from homogentisic acid (HGA). We report that C. neoformans strains representing all four serotypes can produce a brown pigment from HGA. The brown pigment was acid resistant and had the electron paramagnetic resonance spectrum of a stable free radical, qualities that identified it as a melanin. Melanin “ghost”-like particles obtained from pigmented C. neoformans cells were hydrophobic, fluorescent under a variety of irradiation wavelengths, negatively charged, insoluble in organic solvents and alcohols, resistant to degradation by strong acids, and vulnerable to bleaching. HGA melanization was laccase dependent and repressed by high concentrations of glucose. The ability of C. neoformans to utilize a bacterial melanin precursor compound suggests a new substrate source for melanization in the environment.

Report this publication

Statistics

Seen <100 times