Fig 6. Scarless deletion by recombineering with oligonucleotides.

(A) Strategy. The target gene is replaced by recombineering with the tetA landing pad. The landing pad is then replaced by recombineering with short, synthesized oligonucleotides and counterselection with 6 mM NiCl₂. (B) Agarose gel electrophoresis of colony PCR products verifying deletion of rrnB. Lane 1: Wildtype rrnB (WT); Lane 2: tetA landing pad integrant; Lanes 3–10 8 randomly sampled colonies after deletion. (C) Sequencing result after deletion compared to the original sequence. Targeted homology regions are indicated by the same color scheme as in (A).