FIG. 1.

Schematic representation of the dual-origin plasmid used to construct mutants carrying deletions and substitutions in the CIS and ori regions of the IncB replicon and to determine their relative copy numbers. Features important for the use of this plasmid and its derivatives are shown. RNAI, antisense RNA regulating the expression of repA of the pMU720 replicon; RNAII, repA-mRNA; CAT, gene for CAT conferring resistance to chloramphenicol; Ap^R, gene conferring resistance to ampicillin (bla). The triangles denote transcription terminators; ▸, T4 gene 32 terminator; , pheR terminator. Unique restriction endonuclease sites are shown in boldface.