Putrescine-mediated degradation of ribonucleic acid in chloramphenicol-treated Escherichia coli.

Escherichia coli treated with chloramphenicol (CM) accumulated ribonucleic acid (RNA) in the absence of protein synthesis. The accumulated RNA (CM-RNA) was largely ribosomal (23S and 16S) and soluble (4S). The stability of CM-RNA depended upon the incubation conditions following the removal of CM. Thus, conditions which allowed the complete recovery of cultures from CM inhibition resulted in only a 30% loss of CM-RNA. The addition of proflavine to recovering cultures, which prevented further RNA synthesis, also resulted in about 30 to 35% degradation of CM-RNA. However, when RNA synthesis was inhibited by starving the recovering cultures for the required amino acid, histidine, 55% of the CM-RNA was degraded. The decreased stability of CM-RNA in histidine-starved cultures appeared to be due specifically to the intracellular buildup of putrescine. Under the above conditions of incubation, that RNA which was stable sedimented in sucrose gradients as 23S, 16S, and 4S RNA. It is suggested that intracellular putrescine plays a role in the stability of ribosomal RNA accumulated during CM treatment.