Holloman W K, Radding C M
Proc Natl Acad Sci U S A. 1976 Nov;73(11):3910-4. doi: 10.1073/pnas.73.11.3910.
When a mixture of superhelical DNA (RFI) of phage phiX174 am3 and fragments of single-stranded DNA from wild-type phiX174 was added to spheroplasts of E. coli carrying an amber suppressor, several percent of the progeny phage were recombinant. The yield of wild-type progeny was 10(3) to 10(4) times lower when the fragments came from phiX174 am3 or phage G4 am+, or when fragments were absent. Fewer recombinants were produced in proportion to the decrease in the fraction of RFI in samples treated with S1 nuclease, whereas the total yield of phage did not decrease. Transfection by fragments and superhelical DNA produced 20 to 100 times more recombinants than transfection by fragments and either nicked circular DNA or relaxed closed circular DNA. Transfection of a recA- strain by RFI DNA and fragments yielded 5-10% as many recombinants as transfection of a rec+ strain. This partial requirement for recA was bypassed by transfection with complexes of RFI AM3 DNA and am+ fragments made in vitro.
当将噬菌体phiX174 am3的超螺旋DNA（RFI）与野生型phiX174的单链DNA片段的混合物添加到携带琥珀抑制基因的大肠杆菌原生质球中时，有百分之几的子代噬菌体是重组体。当片段来自phiX174 am3或噬菌体G4 am+，或不存在片段时，野生型子代的产量要低10³到10⁴倍。在用S1核酸酶处理的样品中，与RFI比例的降低成比例地产生的重组体减少，而噬菌体的总产量并未降低。与用片段和带切口的环状DNA或松弛的闭环DNA转染相比，用片段和超螺旋DNA转染产生的重组体多20至100倍。用RFI DNA和片段转染recA⁻菌株产生的重组体数量是转染rec⁺菌株的5-10%。用体外制备的RFI AM3 DNA和am⁺片段的复合物进行转染绕过了对recA的这种部分需求。
