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Decay of Ribonucleic Acid Synthesis in Amino Acid-Starved Escherichia coli After Rifampin Treatment

^a Albert Einstein Medical Center, Philadelphia, Pennsylvania 19141

ABSTRACT

The concentration of rifampin necessary to affect the initiation of ribonucleic acid (RNA) synthesis quickly in Escherichia coli strains K-12 and 15TAU was about 200 µg/ml, as determined by extrapolation of the effect of the drug on the induction of ß-galactosidase synthesis. A lag in the action of rifampin of about 10 s was confirmed. Rifampin was then used as a probe to compare RNA synthesis in growing and amino acid-starved E. coli. Restoring arginine to arginine-starved strain 15TAU immediately after rifampin inhibition did not detectably restore the rate of uracil uptake to that of uninhibited cells. The residual rate of RNA synthesis (corrected for acid-soluble triphosphate specific activities) after rifampin treatment of both growing and isoleucine-starved (valine-inhibited) cultures of strain K-12 showed similar decay kinetics. These findings support the notion that amino acid starvation blocks the initiation of some RNA transcription units, but do not rule out other possibilities.

¹ Present address: Biology Department, Bryn Mawr College, Bryn Mawr, Pa. 19010.