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The Production and Characterization of Ultraviolet-Induced Mutations in Aspergillus terreus. II. Cultural and Morphological Characteristics of the Mutations

Kenneth B. Raper, Robert D. Coghill and Alexander Hollaender
American Journal of Botany
Vol. 32, No. 3 (Mar., 1945), pp. 165-176
Stable URL: http://www.jstor.org/stable/2437538
Page Count: 12
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Production and Characterization of Ultraviolet-Induced Mutations in Aspergillus terreus. II. Cultural and Morphological Characteristics of the Mutations
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Abstract

Conidia of a selected strain of Aspergillus terreus were exposed to ultraviolet radiation, and random isolations were made from colonies resulting from irradiated cells. Approximately two hundred of these were cultivated upon a variety of agar media to determine the effect of the substratum upon growth and attendant cultural characteristics. The majority of isolates from irradiated spores, normal appearing and cultural mutants alike, remained stable when recultivated through ten successive culture generations upon Czapek's solution agar. Eleven types of mutations were recognized. One of these resulted from an inability of the mutant to produce thiamin. Another was unable to utilize nitrate nitrogen but developed normally if supplied with ammonia or amino nitrogen. In other cases mutations were more strictly morphological and consisted of a total or partial loss of color from the conidial heads without apparent alteration in physiology. In still other and more numerous cases, both morphological and physiological changes were observed. Cultural and morphological differences commonly reflected basic physiological or biochemical changes. Of more than 200 isolates resulting from irradiated spores tested for the production of itaconic acid, only 14 produced yields greater than the parent strain. Among this number only two appeared as cultural mutants, and only one of these was markedly different from the parent strain. The production of ultraviolet-induced mutations appears to offer definite, if somewhat limited, possibilities of increasing yields of itaconic acid from Aspergillus terreus.

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