The kinetics of ribonucleic acid (RNA) and protein synthesis in rifampicin-inhibited normal and ethylenediaminetetraacetic acid (EDTA)-treated Escherichia coli was measured. Approximately 200-fold higher external concentrations of rifampicin were needed to produce a level of inhibition in normal cells comparable to that observed in EDTA-treated cells. The rates of RNA and protein synthesis in both kinds of cells decreased exponentially, after an initial lag phase, at all rifampicin concentrations tested. The lag phase was longer and the final exponential

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Phage mutants of T4 have been isolated which can multiply only on Escherichia coli strains which contain a missense suppressor which is known to cause the substitution of glycine for arginine in response to the AGA codon. Mutations producing the suppressible phenotype were mapped and shown to occur in six different phage cistrons. Two of the cistrons were concerned with deoxyribonucleic acid synthesis, two were concerned with phage structural components, and two were concerned with functions required for growth in E. coli K-12 but not in E. coli B. The burst size of the different phage mutants grown on strains carrying the same suppressor was dependent upon the efficiency of suppression, which in turn is known to be dependent upon the glycyl-transfer ribonucleic acid synthetase activity.