An analysis of the free intracellular amino acids of certain strains of Neurospora

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1. 1. Free intracellular amino acids were demonstrated to be present as a definite cell fraction of Neurospora crassa. 2. 2. Some 35 ninhydrin-positive substances were encountered among 28 different strains analyzed; however, none of the strains had all of these substances present in their extracts. In some mutants internal free amino acids were found to be associated in their expressions with mutant characteristics. In other mutants, certain amino acids were consistently absent. Other apparent differences disappeared in backcrosses to wild type, and new amino acids showed up. 3. 3. When certain strains were backcrossed to wild type to the F 5 generation, results showed that a characteristic free intracellular amino acid pattern is associated with the genotype of the mutant that controls the mutational deficiency. Up into the F 5 generation, differences in the amino acid pool stayed consistent and were not lost on backcrosses to wild type. This indicates that the amino acid pattern must be related to the particular phenotype brought about by a single gene mutation, 4. 4. From a cross between a methionine-less mutant and an adenine-less purple pigment mutant, all possible F 1 segregants were obtained. Several strains of each recombination of segregants were tested by chromatography for both qualitative and quantitative differences in their free intracellular amino acid pattern. Differences appeared to be peculiar to each of these types of F 1 progenies. Some minor differences existed between strains that had the same mating type and growth factor requirement, but in the general pattern this experiment proved again the conclusion that was drawn from the F 5 experiment with backcrosses to wild type. 5. 5. When the wild-type strain Em5297a was grown on different supplements, such as amino acids, purine, or vitamins, a number of changes in the free intracellular amino acid fraction were observed.