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Appl. Environ. Microbiol., May 1995, 1968-1975, Vol 61, No. 5
T Caesar-Tonthat, F Van Ommen Kloeke, GG Geesey and JM Henson
Gaeumannomyces graminis var. graminis, a filamentous soil ascomycete,
exhibited enhanced cell wall melanin accumulation when exposed to as little
as 0.01 mM CuSO(inf4) in minimal broth culture. Because its synthesis was
inhibited by tricyclazole, the melanin produced in response to copper was
dihydroxynaphthalene melanin. An additional hyphal cell wall layer was
visualized by electron microscopy when hyphae were grown in the presence of
copper and fixed by cryotechniques. This electron-dense layer was between
the outer cell wall and the inner chitin layer and doubled the total wall
thickness. In copper-grown cells that were also treated with tricyclazole,
this electron-dense layer was absent. Atomic absorption spectroscopy
demonstrated that up to 3.5 mg of Cu per g of fungal mycelium was adsorbed
or taken up by hyphae grown in 0.06 mM CuSO(inf4). A method for silver
enhancement was developed to determine the cellular location of CuS. CuS
was present in cell walls and septa of copper-grown hyphae. Electron
microscopy of silver-stained cells suggested that CuS was associated with
the melanin layer of cell walls.
Copyright © 1995, American Society for Microbiology
Melanin Production by a Filamentous Soil Fungus in Response to Copper and Localization of Copper Sulfide by Sulfide-Silver Staining
Department of Microbiology and Engineering Research Center, Montana State University, Bozeman, Montana 59717
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