Schematic representation of phoA constructs. A. The different sections, including the ltuf promoter, the signal sequence, the acylation sequence and the phoA gene, were combined by overlap extension PCR as described in the text and ligated between the Not I and Bam HI sites in pISM2062.2. The site of the IR oligonucleotide linker is shown. The positions of the oligonucleotide primers (Table 1) are also shown. B. The construct produced containing only the ltuf promoter and pho A gene. IRL: inverted repeat oligonucleotide linker, N: Not I cleavage site, B: Bam HI cleavage site, ATG: translational start codon.