FIG. 1.
Strategy used to alter expression of las genes. (A) Schematic presentation of the chromosomal las operon in MG1363 and of the DNA fragments which have been cloned in pHWA182. The bent arrow indicates the native promoter Plas of the operon. The heavy black line indicates the DNA fragment upstream of the operon. The truncated pfk region is indicated by the light gray line. (B) The synthetic promoter CP25 was flanked by the upstream region of the las operon and the truncated region of pfk on the E. coli vector pHWA182. (C) After selection for erythromycin resistance and subsequent counterselection with ampicillin, the native promoter Plas was replaced by CP25 by double homologous recombination between pHWA182 and MG1363, resulting in HWA217.