[Stimulation of rna synthesis by chloramphenicol].

The influence of different concentrations of chloramphenicol on the RNA synthesis was studied in E. coli strains CP 78 (rel+) and CP 79 (rel-). In cells growing in the medium with succinate as a carbon source the maximal stimulation of RNA synthesis was obtained in the presence of 5-10 mug/ml of chloramphenicol-that is when the protein synthesis in the cells is decreased to 50-30%. Concentrations of antibiotic 50-100 mug/ml only slightly stimulate the incorporation of 14C-uracil in TCA-insoluble fraction. The high level of RNA synthesis once achieved in the presence of small doses of chloramphenicol was not affected by higher concentrations of antibiotic up to 105 mug/ml. It is suggested that at low doses of chloramphenicol some proteins of positive control of RNA synthesis are synthesized. Under amino acids starvation in the presence of succinate only rel+ cells stopped RNA synthesis. The phenotypic suppression of RNA synthesis with chloramphenicol in these cells is achieved only by high concentrations of antibiotic (50-100 mug/ml). It is proposed that under amino acid starvation RNA synthesis is independent on the protein formation and is determined by relative contents of programmed ribosomes in cells.