Inhibition of proline synthesis by tetracycline in Escherichia coli.

Proline is synthesized from glutamic acid by way of the intermediate glutamic -y-semialdehyde, as in the following equation: glutamic acid + glutamic 'y-semialdehyde -* proline. In Escherichia coli W, the first reaction is subject to endproduct inhibition by proline (A. Baich and D. J. Pierson, Biochim. Biophys. Acta 104:397, 1965). This reaction is also inhibited by low, although higher than bacteriostatic, concentrations of chloramphenicol and streptomycin (A. Baich, Bacteriol. Proc., p. 83, 1966). End-product inhibition and susceptibility to antibiotics are evidently correlated, because a decrease in sensitivity to proline is invariably accompanied by a decrease in sensitivity to antibiotics. We now find that the synthesis of glutamic 'y-semialdehyde, and, thus, of proline, is sensitive to bacteriostatic concentrations of tetracycline,