Fig. 3
Recombination frequency of pBMBTmini. a Structure of the recombination cassette and the resulting product after recombination. Arrows indicate the direction of transcription; spc spectinomycin-resistance gene, Pgfp the promoter of the kanamycin-resistance gene, gfp gene encoding green fluorescent protein. b Observation of BMB171 (pBMBTmini + pBMBmob1) before and after recombination. PC phase-contrast microscopy; GFP fluorescence microscopy. Bar indicates 10 μm. c Restriction enzyme digestion of substrate plasmid before and after recombination; M1 λDNA/HindIII marker; M2 Trans2 K Plus DNA marker.1, before recombination, substrate plasmid pBMBTmini; 2–3, from two single SpcS colonies after recombination; 4, before recombination, substrate plasmid pBMBTmini, digested with BamHI; 5–6, from two single SpcS colonies after recombination, digested with BamHI; v vector, 6.5 kb; nr non-recombined cassette, 2.6 kb. r recombined cassette, 1.3 kb. d Increase of the percentage of antibiotic-resistance excision colonies over the number of generations