STUDIES ON THE INHIBITION OF GROWTH OF ESCHERICHIA COLI BY NORMAL AMINOBUTYRIC ACIDS

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Abstract
The influence of normal butyric acids with an amino group on either the alpha, beta, gamma, or alpha, gamma positions on the growth of E. coli B and several auxotrophs was studied. All compounds except gamma-aminobutyric acid were inhibitory. In the wild type, inhibition of growth by alpha-aminobutyric acid was relieved mainly by intermediates on the valine-leucine biosynthetic pathway, diaminobutyric acid inhibition by intermediates involved in methionine and arginine biosynthesis and beta-amino-butyric acid inhibition by beta-alanine or pantothenate. Studies with auxotrophs revealed an interference with leucine biosynthesis due to competition between alpha-ketobutyrate and alpha-ketoisovalerate, an interference by diaminobutyrate with the utilization of the alpha-amino acid in mutants requiring isoleucine, isoleucine plus valine, or methionine, and a similar effect by beta-aminobutyric acid on beta-alanine utilization. The relatively larger concentrations of alpha-amino or diaminobutyric acid required to inhibit wild type organisms suggests an additional effect at non-specific loci such as during transport into the cell, or due to displacement at various levels of protein synthesis. In dense cell suspensions of wild type E. coli, alpha-aminobutyric acid was most effective in interfering with the intracellular accumulation of K in high cation media and in displacing it in low cation media. Further, mainly this cation could influence the lag and maximum obtainable level of growth in the presence of high concentrations of alpha-aminobutyrate, when tested with optimum amounts of K which exerted no influence on the normal growth rate.