Fig 2.

Mutagenesis test system. The direct repeat originating from the gudB allele of B. subtilis was placed as the spacer between an optimal −10 and −35 region (upper part). An operon consisting of a kanamycin resistance gene (aphA3) and the β-galactosidase gene (lacZ) was placed under the control of the artificial promoter. Due to the long spacer, the promoter is not active. By the precise deletion of 9 bp in the spacer region, the promoter gains function, and the kanamycin resistance and the β-galactosidase are highly expressed (lower part).