SUMMARY: The ability of glycine to induce L-phase of bacteria did not apply to group A β-haemolytic streptococci. In the presence of penicillin, glycine in a bacterial inhibitory concentration had a notably additive L-phase inducing property for streptococci. Reasons are given to support the view that this activity of glycine is limited to the induction of L-phase growth. A sharp increase in the yield of L-phase colonies was also observed when serine, threonine, methionine or alanine were tested under similar conditions. When the effectiveness of the racemate and both the isomers of these amino acids was compared, the d-isomer was the active substance in most cases. In one strain, the L-inducing and bacterial inhibitory action of the racemate and both isomers of methionine was tested simultaneously. The yield of L-phase colonies was found to be inversely proportional to the effect of the different stereoisomers on bacterial growth.

d-Cycloserine had a weak L-inducing effect on group A streptococci, but the combined action of d-cycloserine and glycine or dl-serine was equal to that obtained with penicillin and the same amino acids. Propagation of these L-phase organisms was possible in the presence of 1% (w/v) glycine and within a narrow range of concentrations of d-cycloserine. The additive effect of the amino acids cited towards penicillin and d-cycloserine for the induction of L-phase structures can be explained by the antibiotic property of high concentrations of glycine and some of the d-amino acids.


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