Effects of chloramphenicol on the transcriptional activities of ribosomal RNA and ribosomal protein genes in Escherichia coli

Abstract

Treatment of the bacterium Escherichia coli with the antibiotic chloramphenicol results in accumulation of stable RNA in excess of total protein. This condition is exploited in order to study the relationships between ribosomal RNA and ribosomal protein gene expression. The results indicate that at low concentrations of chloramphenicol RNA accumulation is stimulated slightly and protein synthesis remains virtually unaffected. The syntheses of individual ribosomal proteins are co-ordinately stimulated so that the balance between rRNA and ribosomal protein production is maintained. At higher drug concentrations protein synthesis is inhibited; with increasing levels of inhibition, ribosomal protein synthesis represents an increasingly greater fraction of the residual protein synthesized but individual ribosomal proteins are produced in non-co-ordinate amounts. It is further shown that chloramphenicol treatment results in accumulation of ribosomal protein messenger RNA; this means that the synthesis of ribosomal protein mRNA is insensitive to the drug. The amount of ribosomal protein mRNA that accumulates is related to the degree of disparity between RNA and protein accumulation. At chloramphenicol concentration above 1·0 μg/ml, 1·5 to 2·0% of the total cellular RNA is ribosomal protein mRNA.