Expression vector. Expression vector pUCHelNhaD. H. elongata nhaD (nhaD) was amplified by PCR using mutated primers that integrate the nhaD start codon in a constructed Nde I restriction site. The gene was subsequently cloned between the Nde I and Aat II enzyme sites of pUC18. The pUC18 β-lactamase gene is destroyed by this insertion, and in frame replaced by nhaD. Expression of NhaD is controlled by the lac operator (lac). Amp depicts the gene encoding for ampiciline resistance, ori marks the E. coli replication origin.