Figure 3.
The R1-19 plasmid is nicked at oriT in the absence of recipient cells. Culture medium containing no cells (lane 4); 60, 120, or 240 μl of recipients alone (lanes 1–3, respectively); 60, 120, 240, and 480 μl of J5[R1-19] alone (lanes 5–8); or a mating mixture of J5[R1-19] and a recipient following 15 min of incubation at 37°C (lanes 9–12) was processed for runoff DNA sequencing as described. The number of plasmid-carrying cells in reaction mixtures containing either donor alone or the mating mixture was the same. The position of oriT-terminated reaction products is indicated by the R1 nucleotides C-2040 and A-2041 (numbering as in ref. 21), which complement the nick site within the consensus 3′-TCGTGG↓TGTGG-5′ (3).