Influence of Thymine Starvation on the Integrity of Deoxyribonucleic Acid in Escherichia coli

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RESUMO

The influence of thymine starvation on the single-strand molecular weight of deoxyribonucleic acid (DNA) from Escherichia coli was determined by sedimentation through gradients of alkaline sucrose. Growth of cells for as long as 150 min in thymineless medium did not significantly reduce the molecular weight below the control value of 2.4 ± 0.3 × 108 daltons. Incubation of cells in thymineless medium after exposure to 500 ergs/mm2 of ultraviolet light or 20 krad of 137Cs gamma rays did not appear to block the rejoining of single-strand breaks associated with irradiation. Thus, DNA repair enzymes, presumably including DNA ligase, are not significantly inhibited by thymine starvation.

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