NUCLEIC ACID METABOLISM AND RIBONUCLEIC ACID HETEROGENEITY IN ESCHERICHIA COLI

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Abstract
P32 is readily incorporated into the ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) phosphorus of normal broth-grown E. coli strain B at rates reflecting the rates of synthesis of these substances, i.e., reflecting the age of the culture. No turnover of RNA or DNA was observed at any culture age. As with RNA from T2 bacteriophage-infected bacteria, normal bacterial RNA was heterogenous in that RNA s dissimilar in specific activity are isolated when cells briefly exposed to P32 are disrupted and separated by centrifugation into 2 particulate fractions (P1 and P2) and a soluble fraction (S). RNA in the P1 fraction constitutes less than 5% of the total RNA but attains the highest specific activity. RNA in the soluble fraction is intermediate. The RNA fractions also exhibit dissimilar changes in specific activity after p32 is no longer available to the cells. RNA mononucleo-tides in the fraction from normal cells become uniformly labeled, but those from infected cells do not, indicating an even greater heterogeneity of the RNA in phage-infected cells.

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