A SOFT X-RAY MUTANT OF ASPERGILLUS NIGER VAN TIEGHEM

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Abstract
A colony of A. niger was subjected to soft X-rays from a Cu target. An atypical strain of A. niger was isolated from the irradiated culture. Pigmentation in this mutant strain was practically absent, sporulation very much depressed, and growth rate much slower than for the normal strain. The mutant was much more efficient in production of citric acid from glucose, and more responsive to several individual growth substances, indicating a general reduction ir its rate of synthesis of these substances. Quantitatively the mutant shows a significant deviation from the normal with respect to mat conten of several amino acids of 14 tested. Analysis of the total nucleic acid content of the mold mats showed a significantly decreased amt. of nucleic acid per unit mat wt. in the mutant. There was no distortion of the desocyribosenucleic acid/ribose-nucleic acid ratio in the mutant nucleic acid as compared with that of the normal strain. When harvested at 7 days, metaphos-phate was found present in the normal strain but not in the mutant.

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