FIG. 1.
Schematic representation of the procedure for deleting the chromosomal mexAB-oprM genes and subcloning DNA fragments into shuttle vector pMMB67EH. (A) Deletion of chromosomal mexAB-oprM. NotI-treated pNOT19-ΔABM was ligated to the NotI site of pMOB3, and the resulting pΔMexA,B-OprM was inserted into chromosomal mexAB-oprM by homologous recombination. The transconjugant was Kmr and sucrose-sensitive and contained an unwanted DNA fragment, which was excised by selecting for sucrose resistance (29). (B) Physical mapping of the restriction fragments subcloned into the shuttle vector. Solid lines represent the restriction fragments cloned into pMMB67EH (pMEXE1, pMEXF1, pOPRN1, pMEXEF1, and pMEXEF-OPRN1) and pVLT33 (pMEXEF-OPRN-KM1). Physical distances of the lines to the mexEF-oprN genes are arbitrary.