An Unstable Strain of Aspergillus foetidus Segregating Proline Auxotrophs |
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Authors: | L. T. Chang and R. W. Tuveson |
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Abstract: | Two basic colony types have been obtained through single conidial isolation from the Bode strain of Aspergillus foetidus as well as from mutants of this unstable strain. Type I is prototrophic whereas type II is an auxotroph requiring proline. When a type I strain is grown on complex medium it gradually becomes overwhelmed by type II sectors of growth. However, essentially pure cultures of type I can be maintained on minimal medium (lacking proline). The yield of glucoamylase from type II cultures is less than half that obtained with type I cultures. The instability of type I cultures when grown on complex medium can not be explained by heterokaryosis or the presence of virus-like particles found in the original Bode strain and its derivatives. The isolation of five stable prototrophic strains obtained as more rapidly growing sectors from type I subcultures grown on complex medium suggests that the instability most probably results from a duplicated chromosomal segment or other chromosomal aberration analogous to those described in A. nidulans. |
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