The Effect of Amino Acids on the Microbial Growth Inhibition Produced by Thienylalanine”

A recent paper from this laboratory (1) reported the inhibition of the growth of Saccharomyces cerevisiae by &3-2-thienylalanine, an isostere of phenylalanine. This inhibitory action of thienylalanine was counteracted by phenylalanine. Thus, the thienylalanine was shown to act as an “antiphenylalanine” for this yeast. Tyrosine had no effect on the toxicity of the thienyl compound. Furthermore, a mixture of most of the other natural amino acids present in twice the concentration of phenylalanine required for reversal did not nullify inhibition of yeast growth by thienylalanine. This indicated that no other amino acid was so effective as phenylalanine in the prevention of the yeast growth inhibition due to thienylalanine but it did not exclude the possibility that, at much higher levels, other amino acids might counteract this toxicity. We wish to report here the effects of thienylalanine on Streptococcus faecalis, Lactobacillus arabinosus 17-5, Escherichia coli, and Saccharomyces cerevisiae, and the effects of high concentrations of most of the known naturally occurring amino acids on the inhibitory action of thienylalanine on the last two organisms.