Regulation of Ribosomal and Transfer Ribonucleic Acid Synthesis in Escherichia coli B/r

The relative rates of tRNA, rRNA, and DNA synthesis were measured for steady state cultures of Escherichia coli B/r growing in succinate and glucose minimal media which support growth rates of 0.67 and 1.46 doublings per hour, respectively. Following a 2-fold increase in growth rate, the rate of tRNA synthesis increased approximately 2-fold relative to the rate of DNA synthesis and decreased 10 to 15% relative to the rate of rRNA synthesis. It is concluded that the synthesis of tRNA is regulated in a manner similar to the mechanism regulating rRNA synthesis. The 10 to 15% difference in the relative rates of synthesis is not the result of an increase in the relative frequency of ribosomal RNA cistrons at the higher growth rates, and therefore it seems that the mechanisms controlling rRNA and tRNA synthesis are at least partially independent.