INHIBITION OF PIGMENTATION IN ASPERGILLUS NIGER BY DIMETHYLSULFOXIDE

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Abstract
Since, among those tested, only those compounds having the sulfoxide radical Inhibited pigmentation, the sulfoxide part of the molecule appears responsible for the color inhibition. Increased inhibition with increasing concentration of dimethylsulfoxide (DMSO) (4,000 ppm) indicated a competitive type of inhibition. The change from white to light brown after 4 or 5 days may have resulted from the oxidation of materials on the surface of the conidla or activation of another metabolic pathway to partially overcome the Initial inhibition. The metabolic pathway responsible for pigmentation is apparently not directly required for overall growth, since neither growth rate nor sporulatlon was affected until concentrations of DMSO or L-cystelne well In excess of those required for pigment Inhibition were used. Pigmentation, therefore, appears to be a superfluous characteristic relative to the life cycle of A. niger. This was further indicated by the normal growth and viability oi nonpigmented spores.