HEREDITARY VARIATION AND GENETIC RECOMBINATION IN KOJI-MOLDS (ASPERGILLUS ORYZAE AND ASP. SOJAE)

III. BIOCHEMICAL MUTATION

Abstract

1. The leucineless and histidineless mutant strains of Asp. Sojae which proved to be comparatively stable, were irradiated with ultraviolet light, and the following double auxotrophic mutants were isolated by total isolation and starvation techniques.
From strain 10C his: requiring reduced nitrate (11 strains), arginineless (2), and methionineless (1).
From strain 14C leu: requiring reduced nitrate (23), arginineless (1), histidineless (1), lysineless (1), methionineless (2), nicotinic-less (1), and adenine- or hypoxanthineless (1).
2. The starvation technique was effective for isolating double auxo trophs from some strains.
3. Among the mutant types selected by the starvation technique, the reduced nitrate strains were obtained in exceedingly high frequency (37 mutants out of 51 double auxotrophs).
4. In Koji-molds (Asp. Oryzae and Asp. Sojae) the most frequent deficient types have been found to be arginineless, histidineless, lysineless, and methionineless mutants.
5. Among single auxotrophs, lysineless, histidineless, and leucineless mutants were comparatively stable, but other mutants showed frequent spontaneous reversion.
6. Double auxotrophs proved to be more stable than single auxotrophs-in such genetic characters as colony type and nutritional requirement.