Dreisig H, Riise E, Nordström K
Mol Gen Genet. 1981;182(1):148-53. doi: 10.1007/BF00422782.
Specialized transducing lambda phages, lambda oriR1, harboring DNA from the resistance plasmid R1drd-19 and its copy mutant pKN103 were isolated. From measurements of CCC-DNA content it is concluded that upon infection the phages can establish themselves as self-replicating plasmids in recA hosts lysogenic for lambda. It is thought that this bypassing of lambda immunity is due to the presence of the R1 origin of replication. The plasmids are sensitive to the incompatibility expressed by plasmid R1. This has been shown mainly by transduction of lambda oriR1 into recipients containing R1 plasmids or plasmid pBR322 carrying the basic replicon. We were able to demonstrate that a copy mutant of plasmid R1 was insensitive to copA+, but sensitive to the concerted action of PstI fragments F1 and F2. This mutant was previously assumed to be of dominant type. Physical mapping of the lambda oriR1 derivatives verified that they carry the basic replicon of plasmid R1. The plasmids are not stably maintained, but are lost in a frequency of 1%-2% per cell generation, which is consistent with their lack of the R1par region.
分离出了携带来自抗性质粒R1drd - 19及其复制突变体pKN103的DNA的特异性转导λ噬菌体λoriR1。通过对共价闭合环状DNA（CCC - DNA）含量的测量得出结论，在感染后，这些噬菌体能够在对λ溶原的recA宿主中作为自我复制质粒建立自身。据认为，这种对λ免疫的绕过是由于R1复制起点的存在。这些质粒对质粒R1所表达的不相容性敏感。这主要通过将λoriR1转导到含有R1质粒或携带基本复制子的质粒pBR322的受体中来证明。我们能够证明质粒R1的一个复制突变体对copA +不敏感，但对PstI片段F1和F2的协同作用敏感。该突变体先前被认为是显性类型。对λoriR1衍生物的物理图谱分析证实它们携带质粒R1的基本复制子。这些质粒不能稳定维持，而是在每个细胞世代中以1% - 2%的频率丢失，这与其缺乏R1par区域是一致的。
