The use of RNA/DNA ratio measurements to assess rifampicin-induced growth inhibition of Escherichia coli

Growth rates and cellular levels of RNA, DNA and protein were studied in Escherichia coli during and following exposure to rifampicin, and in the transition from stationary to exponential phase growth in drug-free medium. At rifampicin concentrations of up to twice the MIC, significant changes in growth rates were only apparent after several generations. At higher rifampicin concentrations growth was terminated much more rapidly. In every case changes in growth rates were closely paralleled by corresponding changes in RNA/DNA ratios. These findings suggest the possibility of using RNA/DNA ratio measurements to monitor the drug-induced growth inhibition of other bacteria.