In vitro synthesis of Escherichia coli ribosomal RNA

Synthesis of ribosomal RNA in a cell-free system was achieved using purified Escherichia coli RNA polymerase and bacterial DNA templates from E. coli, Proteus mirabilis and E. coli/P. mirabilis hybrid strains carrying an E. coli DNA enriched for ribosomal RNA genes.Both direct and indirect competition hybridization revealed that from 5 to 15% of the in vitro product, depending on the template used, had sequences homologous to rRNA. The level of synthesis of sequences homologous to rRNA was related directly to the proportion of rRNA genes in the template. The use of heterologous DNA during competition hybridization ensured at least a 100-fold greater sensitivity for the detection of rRNA sequences than from any messenger RNA sequence.