For the cloning of Na+/H+ antiporter genes, Sau3AI-digested genomic DNA from strain NEAU-ST10-25T was electroporated into E. coli KNabc and its transformants were screened on the LBK medium plates containing 0.2?M NaCl. Of several resultant clones, one recombinant plasmid designated pUC-ZD-6 [pUC18 carrying a 4.2-kb DNA fragment (Fig. 1)] enabled E. coli KNabc to grow on the LBK medium plate containing 0.2?M NaCl, which is the upper limit of NaCl tolerance concentrations for E.
