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首页> 外文期刊>Journal of bacteriology >Effects of Ribonucleosides on Thymidine Incorporation: Selective Reversal of the Inhibition of Deoxyribonucleic Acid Synthesis in Thymineless Auxotrophs of Escherichia coli
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Effects of Ribonucleosides on Thymidine Incorporation: Selective Reversal of the Inhibition of Deoxyribonucleic Acid Synthesis in Thymineless Auxotrophs of Escherichia coli

机译：核糖核苷对胸苷掺入的影响：选择性逆转大肠杆菌无胸腺营养素中脱氧核糖核酸合成的抑制作用。

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摘要

Addition of certain ribonucleosides to exponentially growing cultures of Escherichia coli increased the extent of thymidine incorporation. The prolonged uptake of thymidine was correlative with the ability of these ribonucleosides to prevent the degradation of thymidine. In addition to protecting thymidine, uridine reversed partially (70 to 80%) the inhibition of deoxyribonucleic acid (DNA) synthesis in thymineless auxotrophs by cytosine arabinoside, hydroxyurea, and nalidixic acid. This reversal was selective for auxotrophic strains since no reversal of inhibition by uridine was observed in any of the prototrophic strains examined. In the presence of uridine, the rapid assimilation of thymidine by prototrophic and auxotrophic strains was prevented and the rate of DNA synthesis became a function of the available exogenous thymidine. Under these conditions, prototrophic strains accumulated equivalent amounts of thymidine into the acid-soluble (pool) and acid-insoluble (DNA) cell fractions. In contrast, 95 to 98% of the thymidine taken up by auxotrophs was found in the acid-insoluble (DNA) cell fraction. The results suggest that different mechanisms for DNA synthesis exist in auxotrophs and prototrophs. Based on these observed differences, some possible mechanisms for the selective reversal of the inhibition of DNA synthesis in auxotrophs are discussed.
机译：向大肠杆菌的指数生长培养物中添加某些核糖核苷可增加胸苷掺入的程度。胸腺嘧啶核苷的延长摄取与这些核糖核苷防止胸腺嘧啶核苷降解的能力有关。除保护胸苷外，尿苷还部分逆转了（70％至80％）胞嘧啶阿拉伯糖苷，羟基脲和萘啶酸对无胸腺营养缺陷型中脱氧核糖核酸（DNA）合成的抑制作用。这种逆转对于营养缺陷型菌株是选择性的，因为在所检查的任何营养缺陷型菌株中均未观察到尿苷抑制作用的逆转。在尿苷存在下，可防止原养和营养缺陷型菌株对胸苷的快速同化，并且DNA合成速率成为可用外源胸苷的功能。在这些条件下，原养型菌株将等量的胸苷积聚到酸溶性（池）和酸溶性（DNA）细胞级分中。相反，在酸不溶性（DNA）细胞部分中发现营养缺陷型吸收的胸腺嘧啶的95％至98％。结果表明营养缺陷型和原营养型中存在DNA合成的不同机制。基于这些观察到的差异，讨论了选择性逆转营养缺陷型DNA合成抑制作用的一些可能机制。

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