FIG. 1.

Map of plasmid pSH1 and construction of random fdo′-blaM fusions. Plasmid pSH1 was made by ligation of the 5-kb HindIII-SacI fragment from plasmid pHA3 (1) into the corresponding sites in vector pYZ4 (49). The cloned fragment carries the entire fdo locus with its own promoter. Random β-lactamase fusions were subsequently constructed by digesting from the 3′ end of the fdoI gene with exonuclease III and ligating the blunt-ended DNA with the truncated blaM gene.