The assimilation of amino-acids by bacteria. 13. The effect of certain amino-acids on the accumulation of free glutamic acid by Staphylococcus aureus: extracellular peptide formation

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Abstract
The accumulation of free glutamic acid within Staphylococcus aureus, which occurs when the cells are incubated with glutamic acid and glucose, is reduced if aspartic acid, cysteine, alanine or glycine is also present. The presence of either valine or leucine produces an acceleration of the rate of accumulation of free glutamic acid. The inhibition produced by aspartic acid is dependent upon the relative concns. of aspartic and glutamic acids present. The presence of aspartic acid also reduces the rate at which glutamic acid is withdrawn from the medium. The accumulation of aspartic acid within the cells also requires glucose and is inhibited by the presence of glutamic acid. The inhibition produced by cysteine, alanine, or glycine increases as the ratio of each to glutamic acid increases; the inhibition produced by any given ratio depends also on the absolute concns. The decrease in the rate of accumulation of internal free glutamic acid in these cases is accompanied by the formation of combined glutamate in the medium. Chromatographic examination shows that peptide formation has occurred. In the 3 cases the extracellular peptides were hydrolyzed and then gave glutamic acid and cysteine, either alanine or alanine and glycine (2 peptides), and glycine; a polyglycine is also formed in the glycine fraction, but its formation is independent of the presence of glutamic acid. The presence of glucose is essential for the synthesis of these extracellular peptides.