Fig. 3

Schematic of the knock-in reporter system. a A pJW-HDF vector (derivative of pJW) was introduced into NZB at 30 °C. b The single-crossover recombination colonies were selected at 38.5 °C with erythromycin. The single-crossover recombination event occurred in either Hisa region or Hisb region (not shown in schematic). c At 25 °C without antibiotic, the plasmid region in the genome was excised through a second recombination. At the statuses i and ii, the colonies were blue on M17GS-XN plate. At status iii, the colonies were white on M17GS-XN plate. d Representative white colonies (HGK clones) from the blue colonies (plasmid-integrated clones and NZB clones). HDF, heterologous DNA fragment