The Selective Inhibition of Ribosomal RNA Synthesis in E. coli by 2,4-Dinitrophenol

2,4-Dinitrophenol (DNP), when added to cultures of Escherichia coli in concentrations not greatly in excess of those required to inhibit growth, exhibits marked inhibition of RNA synthesis, while little effect on DNA and protein synthesis is seen. The selectivity disappears rapidly with increasing concentrations of DNP. Evidence is presented which demonstrates that low concentrations of DNP inhibit primarily the synthesis of ribosomal RNA with relatively slight effects on the synthesis of messenger and transfer RNA’s. At the concentrations at which selectivity is observed, neither oxidative phosphorylation nor transport of uracil across the cell membrane appears to be affected appreciably by DNP. The similarities and differences between the modes of action of levorphanol and of DNP are discussed.