FIGURE 1.

Introduction of E. coli nhaA into Synechocystis. A, E. coli nhaA under control of the iron-inducible promoter was introduced at a site between slr0370 and sll0337 of Synechocystis chromosome (left panel). During growth in BG11 medium, nhaA is constitutively expressed. Correct insertion of the expression construct was confirmed by PCR on genomic DNA using specific primers a and b; the results are shown in the right panel. WT, wild type; +nhaA, nhaA-expressing cells; Spe, spectinomycin resistance gene. B, disruption of nhaS3 in the strain expressing E. coli nhaA was performed by insertion of the kanamycin resistance gene (Km) into nhaS3. Correct integration of the kanamycin gene was tested by PCR on genomic DNA using specific primers c and d. The results for four independent clones and WT are shown in the right panel. Note that nhaA could not replace nhaS3.