FIG. 1.

(A) Schematic representation of a plasmid for the investigation of initiation and termination functions of the oriT sequence. The deletion of the Tc^r segment occurs when the transfer is initiated and terminated at site 1 and site 2 oriTs, respectively, during mobilization. The duplication of the Tc^r segment occurs when the transfer is initiated at site 2 oriT and terminated at site 1 oriT after passing through an entire round of transfer. The arrowheads indicate the 5′ ends of the nicked strand at oriT. Cm^r, chloramphenicol resistance; oriV, origin of replication. (B) Structure of dual oriT plasmids. Mutant oriT sequences inserted into site 1 and site 2 of the dual oriT plasmids are described in Fig. 2.