Inhibition of ribonucleic acid synthesis by nalidixic acid in Escherichia coli

The effect of low concentrations of nalidixic acid on RNA synthesis in E. coli was examined. It was observed that RNA synthesis in exponentially growing cells was not significantly affected, in harmony with previous studies. However, RNA synthesis was markedly depressed by nalidixic acid during starvation for an amino acid or during chloramphenicol treatment. This effect was not caused by increased killing or inhibition of nucleoside triphosphate synthesis by nalidixic acid. The pattern of radioactive uracil incorporation into transfer RNA or ribosomes was not changed by the drug. The sensitivity of RNA synthesis to nalidixic acid in the absence of protein production 

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may be useful in probing the amino acid control of RNA synthesis.