Selbitschka W, Arnold W, Priefer U B, Rottschäfer T, Schmidt M, Simon R, Pühler A
Lehrstuhl für Genetik, Universität Bielefeld, Federal Republic of Germany.
Mol Gen Genet. 1991 Sep;229(1):86-95. doi: 10.1007/BF00264217.
DNA fragments carrying the recA genes of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae were isolated by complementing a UV-sensitive recA- Escherichia coli strain. Sequence analysis revealed that the coding region of the R. meliloti recA gene consists of 1044 bp coding for 348 amino acids whereas the coding region of the R. leguminosarum bv. viciae recA gene has 1053 bp specifying 351 amino acids. The R. meliloti and R. leguminosarum bv. viciae recA genes show 84.8% homology at the DNA sequence level and of 90.1% at the amino acid sequence level. recA- mutant strains of both Rhizobium species were constructed by inserting a gentamicin resistance cassette into the respective recA gene. The resulting recA mutants exhibited an increased sensitivity to UV irradiation, were impaired in their ability to perform homologous recombination and showed a slightly reduced growth rate when compared with the respective wild-type strains. The Rhizobium recA strains did not have altered symbiotic nitrogen fixation capacity. Therefore, they represent ideal candidates for release experiments with impaired strains.
通过对一株对紫外线敏感的recA⁻大肠杆菌菌株进行互补，分离出了携带苜蓿根瘤菌和豌豆根瘤菌生物变种viciae的recA基因的DNA片段。序列分析表明，苜蓿根瘤菌recA基因的编码区由1044个碱基对组成，编码348个氨基酸，而豌豆根瘤菌生物变种viciae的recA基因的编码区有1053个碱基对，指定351个氨基酸。苜蓿根瘤菌和豌豆根瘤菌生物变种viciae的recA基因在DNA序列水平上显示出84.8%的同源性，在氨基酸序列水平上显示出90.1%的同源性。通过将庆大霉素抗性盒插入各自的recA基因，构建了两种根瘤菌的recA⁻突变菌株。与各自的野生型菌株相比，所得的recA突变体表现出对紫外线照射的敏感性增加，进行同源重组的能力受损，并且生长速率略有降低。根瘤菌recA菌株的共生固氮能力没有改变。因此，它们是用于受损菌株释放实验的理想候选者。
