Figure 1

Construction of two ColE1-derived plasmids, pOri1 (2,811 bp) and pOri2 (4,575 bp). The construction was performed as follows: (A): ColE1 replication origin was amplified from ColE1 plasmid DNA with the indicated primers (white arrow in Fig. 1A). The PCR amplified origin fragment was used for construction of pOri1; (B): The PCR product from step A was linked with an ampicillin-resistance gene to construct a new plasmid pOri1. The whole pOri1 plasmid DNA was amplified with the indicated primer (white arrow in Fig. 1B). The PCR amplified whole pOri1 was used for the construction of pOri2; (C): The PCR amplified whole pOri1 product was linked with ColE1 replication origin fragment from step A again to construct a new plasmid pOri2.