Growth inhibition by L-phenylalanine in Agmenellum quadruplicatum. A clue to some amino acid interrelationships.

Abstract

L-Phenylalanine is a potent inhibitor of growth in a marine species of blue-green bacteria, Agmenellum quadruplicatum. The growth inhibition is reversed by many amino acids when added to the culture medium simultaneously with L-phenylalanine. The most effective L-phenylalanine antagonists are L-tyrosine, L-alanine, L-leucine, L-methionine, L-tryptophan, and L-isoleucine. However, L-tyrosine is the only effective L-phenylalanine antagonist when growth is inhibited by L-phenylalanine for two or more hours prior to addition of an equimolar concentration of the compound tested as an antagonist. Various explanations that could account for inhibition of growth by L-phenylalanine are discussed. Inhibition of growth by L-phenylalanine is not a feature peculiar to the general physiology of blue-green bacteria. For example, the growth of Anacystis nidulans, a fresh water species, was not inhibited by L-phenylalanine, although a different pattern of metabolite sensitivity was found.