RNA metabolism in Escherichia coli infected with bacteriophage T4 : Inhibition of host ribosomal and soluble RNA synthesis by phage and effect of chloromycetin

Abstract

When growing E. coli is infected with a virulent bacteriophage T4, the synthesis of typical ribosomal RNA (16 s and 23 s) and soluble RNA (4 s) stops, and the new phage-specific RNA (phage messenger RNA) is synthesized. In the present work, Chloromycetin (CM) was added either before or after infection and a molecular characterization of RNA synthesized under these conditions was performed. When CM was added before infection, the synthesis of both ribosomal RNA (16 s and 23 s) and soluble RNA (4 s) was demonstrated. The base compositions of these RNAs were the same as those of normal E. coli ribosomal RNA and soluble RNA respectively. The ribosomal RNA, which was a major part of the newly synthesized RNA, was shown to exist as “ribonucleoprotein particles”. These particles are very similar in sedimentation and electrophoretic characteristics to CM particles found in uninfected cells treated with CM. On the other hand when CM was added after infection it did not reverse the inhibition of ribosomal and soluble RNA synthesis. Only phage messenger RNA was synthesized, but the observed amount of this RNA was greater than that in control infected cells without CM treatment. It is suggested that, upon infection, phage synthesizes some specific protein or proteins which cause the inhibition of the synthesis of host ribosomal RNA and soluble RNA.