Genetic Control of Biochemical Reactions in Neurospora: An "Aminobenzoicless" Mutant

Abstract

An x-ray induced mutant strain of Neurospora crassa has been obtained which requires p-aminobenzoic acid for growth. Its growth is a function of the amount of p-aminobenzoic acid supplied, and it is indistinguishable from normal when adequate amounts of p-aminobenzoic acid are available. The mutant differs from normal by a single gene, which must therefore control an essential step in the synthesis of p-aminobenzoic acid, and which is presumably primarily concerned only with the synthesis of p-aminobenzoic acid. Sulfanilamide inhibits the growth of both the normal and mutant strains, and in both cases the inhibition is overcome by an excess of p-aminobenzoic acid. A number of substances related to p-aminobenzoic acid are able to replace it, but their activities are much less than that of p-aminobenzoic acid itself. The addition of benzoic or p-OH-benzoic acids or tyrosine did not increase the amount of p-aminobenzoic acid produced by the normal strain. It is concluded that none of the compounds tested is concerned with the normal synthesis of p-aminobenzoic acid, and that this biosynthesis probably does not involve the introduction of an amino group into a preformed benzene ring.

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