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首页> 外文期刊>Journal of bacteriology >Effect of dna mutations on the replication of plasmid pSC101 in Escherichia coli K-12.
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Effect of dna mutations on the replication of plasmid pSC101 in Escherichia coli K-12.

机译：dna突变对质粒pSC101在大肠杆菌K-12中复制的影响。

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Escherichia coli strains with mutations in genes dnaB, dnaC, and dnaG were tested for their capacity to replicate pSC101 deoxyribonucleic acid (DNA) at a nonpermissive temperature. Only a small amount of radioactive thymine was incorporated into pSC101 DNA in the dna mutants at 42 degrees C, whereas active incorporation into plasmid DNA took place in wild-type strains under the same conditions. The effects of the dnaB and dnaC mutations were greater on plasmid DNA synthesis than on host chromosomal DNA synthesis, suggesting that these gene products are directly involved in the process of pSC101 DNA replication. In dnaG mutants, both plasmid and chromosomal DNA synthesis were blocked soon after the shift to high temperature; although the extent of inhibition of the plasmid DNA synthesis was greater during the early period of temperature shift to 42 degrees C as compared with that of the host DNA synthesis, during the later period it was less. It was found that the number of copies of pSC101 per chromosome in dnaA and dnaC strains, grown at 30 degrees C, was considerably lower than that in wildtype strains, suggesting that the replication of pSC101 in these mutant strains was partially suppressed even under the permissive conditions. No correlation was found between the number of plasmid copies and the tetracycline resistance level of the host bacterium.
机译：测试了在dnaB，dnaC和dnaG基因突变的大肠杆菌菌株在非容许温度下复制pSC101脱氧核糖核酸（DNA）的能力。在42℃下，只有少量放射性胸腺嘧啶被掺入dna突变体的pSC101 DNA中，而在相同条件下，野生型菌株中被掺入质粒DNA中。 dnaB和dnaC突变对质粒DNA合成的影响大于对宿主染色体DNA合成的影响，表明这些基因产物直接参与pSC101 DNA复制的过程。在dnaG突变体中，转移到高温后不久，质粒和染色体DNA的合成都被阻止。尽管与宿主DNA合成相比，在温度转移至42℃的早期，质粒DNA合成的抑制程度更大，但在后期则较小。发现在30℃下生长的dnaA和dnaC菌株中每条染色体pSC101的拷贝数显着低于野生型菌株中的pSC101的拷贝数，这表明即使在允许的条件下，这些突变菌株中pSC101的复制也被部分抑制。条件。在质粒拷贝数和宿主细菌的四环素抗性水平之间未发现相关性。

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