Control of nucleotide metabolism and ribosomal ribonucleic acid synthesis during nitrogen starvation of Escherichia coli.

Ribosomal ribonucleic acid (RNA) synthesis and ribonucleoside triphosphate metabolism were studied in cultures of Escherichia coli subjected to starvation for inorganic nitrogen. In a strain that was under stringent control, a 50-fold reduction in the formation of both 16S and 23S RNA was accompanied by a severe restriction on nucleotide biosynthesis. These inhibitions were relieved in part by incubating the starved cells with amino acids. This result suggests that regulation by the functional RNA control (RC) gene is involved in the effect. This suggestion was confirmed by showing that the effector of the stringent response, guanosine-5'-diphosphate-2'- or 3'-diphosphate ((pp)G(pp)), accumulated at the onset of starvation and disappeared immediately when the amino acids were added. Ribosomal RNA synthesis was severely restricted and the same nucleotide, (pp)G(pp), accumulated at the onset of nitrogen starvation of a relaxed mutant too. These findings suggest that a control mechanism other than the one provided by the functional rel gene might operate to regulate RNA synthesis and that this mechanism is expressed through the synthesis of (pp)G(pp).