The effect of sulphate assimilation on the induction of arylsulphatase synthesis in fungi

Abstract

The liberation of p-nitrophenol from potassium p-nitrophenyl sulphate by certain fungi during growth is inhibited by the addition of cysteine or inorganic sulphate to the culture medium, whereas taurine and choline sulphate have little effect. The arylsulphatase activity of acetone-dried powders of the mycelia of Mucor hiemalis, Aspergillus nidulans, Rhizopus stolonifer and Ustilago scitaminia varied with the sulphur sources used in the culture medium. In general, sulphate, sulphite, thiosulphate, cysteine and methionine gave low arylsulphatase levels whereas taurine, cysteic acid, cysteinesulphinic acid and choline sulphate gave high levels. The response to cysteinesulphonic acid and sulphide varied with each fungus. In a survey of the acetone-dried mycelia of 27 fungi grown on a glucose-peptone-yeast-extract medium only Rhizopus stolonifer, Aspergillus oryzae and Aspergillus nidulans showed arylsulphatase activity. In a chemically defined medium in which taurine was the sole sulphur source all but four of the fungi, Nematospora gossypii, Saccharomyces cerevisiae, Saccharomyces cerevisiae var. ellipsoideus and Sporobolomyces salmonicolar, showed arylsulphatase activity. These findings have been interpreted as a "diauxic" effect in which the inhibitors of arylsulphatase synthesis are metabolized to a common repressor which may be inorganic sulphate.