Effects of Inhibition and Restoration of Protein Synthesis on the Replication of the R Factor R ts 1 in Proteus mirabilis

Abstract

The effect of inhibition of protein synthesis on the replication of the R factor R ts 1 in Proteus mirabilis was examined by using the technique of CsCl density gradient centrifugation. Only 12% of the copies of R ts 1 were found to replicate during amino acid starvation, whereas there was a 30% increase in the amount of P. mirabilis chromosomal deoxyribonucleic acid (DNA) during the same period. Essentially the same amount of R ts 1 and host chromosome replication was observed when chloramphenicol was used to inhibit protein synthesis. The replication of R ts 1 DNA was also examined in experiments in which cultures were starved for amino acids in ¹⁴ N-labeled medium and then transferred to ¹⁵ N-labeled medium containing the required amino acids. These experiments showed that R ts 1 replication took place throughout the first generation in ¹⁵ N-labeled medium and that each copy of R ts 1 was replicated one time during the first generation of chromosomal DNA synthesis in ¹⁵ N-medium.