THE METABOLIC STABILITY OF NUCLEIC ACIDS IN ESCHERICHIA COLI

Abstract

P³²incorporated in ribo- and desoxyribo-nucleic acids during multiplication of Escherichia coli was retained there as nucleotide phosphorus during subsequent generations. There was little or no unequal exchange of P³²between the nucleotides of either nucleic acid during bacterial multiplication. The kinetics of assimilation of inorganic P³²from medium of constant specific activity into the nucleotides of E. coli nucleic acids indicated that phosphorus was incorporated faster into RNA than DNA. E. coli was propagated for two minutes in the presence of inorganic P³²and the rate at which this "two minute" P³²was incorporated into RNA and DNA phosphorus was measured. About 50 to 60 min. was required for both RNA and DNA phosphorus precursor pools to empty. P³²was incorporated into RNA at a faster rate than into DNA. The final ratio RNAP³²/DNAP³²was 50% higher than would be expected from the ratio RNAP/DNAP in E. coli. An equal exchange of phosphorus between RNA and DNA does not occur during bacterial multiplication.