Figure 4
Evaluation of the stability of the cloned DNA using inversion. (a) Schematic diagram of the evaluation of the cloned DNA stability using inversion. TetS, tetracycline sensitive; TetR, tetracycline resistant. (b) Numbers of tetracycline-resistant colonies in the BEST310 system and the iREX system. Error bars, s.d. n = 3. (c) Many tetracycline-resistant recombinants were observed in the BEST310 system. In the iREX system, the same results were obtained in the presence of xylose because of the induced RecA. In contrast, few colonies were observed using the iREX in the absence of xylose. This result indicates that the cloned DNA insert of the iREX is stably maintained due to the strong repression of recA. (d and e) Southern blot analysis using a tet probe revealed changes in the sizes of the signals, indicating the inversion of the BAC1 insert. The genomic DNA of the represented clones was digested with BamHI. In lane M, lambda/HindIII fragments were used as a size marker.