Barany F, Boeke J D
J Bacteriol. 1983 Jan;153(1):200-10. doi: 10.1128/jb.153.1.200-210.1983.
A Staphylococcus aureus plasmid derivative, pFB9, coding for erythromycin and chloramphenicol resistance was cloned into the filamentous Escherichia coli phage f1. Recombinant phage-plasmid hybrids, designated plasmids, were isolated from E. coli and purified by transformation into Streptococcus pneumoniae. Single-stranded DNA was prepared from E. coli cells infected with two different plasmids, fBB101 and fBB103. Introduction of fully or partially single-stranded DNA into Streptococcus pneumoniae was studied, using a recipient strain containing an inducible resident plasmid. Such a strain could rescue the donor DNA marker. Under these marker rescue conditions, single-stranded fBB101 DNA gave a 1% transformation frequency, whereas the double-stranded form gave about a 31% frequency. Transformation of single-stranded fBB101 DNA was inhibited by competing double-stranded DNA and vice versa, indicating that single-stranded DNA interacts with the pneumococcus via the same binding site as used by double-stranded DNA. Heteroduplexed DNA containing the marker within a 70- or 800-base single-stranded region showed only slightly greater transforming activity than pure single-stranded DNA. In the absence of marker rescue, both strands of such imperfectly heteroduplexed DNA demonstrated transforming activity. Pure single-stranded DNA demonstrated low but significant transforming activity into a plasmid-free recipient pneumococcus.
一种编码红霉素和氯霉素抗性的金黄色葡萄球菌质粒衍生物pFB9被克隆到丝状大肠杆菌噬菌体f1中。从大肠杆菌中分离出重组噬菌体 - 质粒杂种，命名为质粒，并通过转化到肺炎链球菌中进行纯化。从感染了两种不同质粒fBB101和fBB103的大肠杆菌细胞中制备单链DNA。使用含有可诱导的常驻质粒的受体菌株研究了将完全或部分单链DNA导入肺炎链球菌的情况。这样的菌株可以挽救供体DNA标记。在这些标记挽救条件下，单链fBB101 DNA的转化频率为1%，而双链形式的转化频率约为31%。单链fBB101 DNA的转化受到竞争性双链DNA的抑制，反之亦然，这表明单链DNA与肺炎链球菌通过与双链DNA相同的结合位点相互作用。在70或800个碱基的单链区域内含有标记的异源双链DNA的转化活性仅比纯单链DNA略高。在没有标记挽救的情况下，这种不完全异源双链DNA的两条链都表现出转化活性。纯单链DNA对无质粒的受体肺炎链球菌表现出低但显著的转化活性。
