The regulatory effect of amino acids on the production of thaxtomin A, a phytotoxin produced by Streptomyces scabies, was investigated. Tryptophan had an important inhibitory effect on the toxin biosynthesis in all five strains of S. scabies tested. Two other aromatic amino acids (tyrosine and phenylalanine) also inhibited thaxtomin A biosynthesis, while aliphatic amino acids did not cause an important decline in thaxtomin A production. Methylation of tryptophan prevented or reduced the inhibitory effect on thaxtomin A biosynthesis. In spite of the inhibitory action of tryptophan and phenylalanine on thaxtomin A production, incorporation of these radiolabeled molecules into thaxtomin A confirmed that they are metabolic precursors for the biosynthesis of the phytotoxin.Key words: thaxtomin A, phytotoxin, Streptomyces scabies, common scab, nitroaromatic compounds, amino acids.
Synthesis and breakdown of universal metabolic precursors promoted by iron
