Synthesis of Ribonucleic Acid by Escherichia coli during Inhibition by Azetidine-2-carboxylic Acid

Abstract

IN bacteria, amino-acids are needed in small amounts for the synthesis of ribonucleic acid (RNA) to occur¹ and, if an amino-acid auxotroph is starved of its required amino-acid, both protein and RNA synthesis cease². However, under certain conditions this ‘stringency’ is not maintained, in that protein synthesis can be sharply retarded while synthesis of RNA is less affected. In Escherichia coli, this differential synthesis of RNA can be brought about by incubation of cells with chloramphenicol³, puromycin⁴, or chlortetracycline⁵, and mutants in which the control of RNA synthesis by amino-acids is ‘relaxed’ have also been described^6,7. Relaxed mutants which require an amino-acid for growth continue to make RNA when starved of their amino-acid requirement; synthesis of RNA in a relaxed strain during inhibition of protein synthesis by 5-methyl tryptophan has also been, demonstrated⁸.