Deletion of cagA gene of Helicobacter pyloriby PCR products

AIM: Cytotoxin-associated protein (antigen) A (CagA) plays an important role in Helicobacter pylori (H pylori) pathogenesis. Our aim was to obtain cagA mutant strains by a new mutation method so as to better understand the mechanism of CagA in epithelial cells.METHODS: In contrast with the traditional method using suicide plasmid, we constructed cagA^- mutant strains directly with PCR products. The constructed mutant clones grew on selective media and allelic exchange was confirmed by Southern blot. Furthermore, two different transformation methods, electroporation, and natural transformation, were compared with regard to theefficiency of recombination.RESULTS: The mutation by PCR products could be completed within 3-5d, and the recombination rate byelectroporation and natural transformation was 4.02×10^-8 and 1.03×10^-9 respectively. Mutation rate by electroporation(4.02×10^-8) was far higher than by natural transformation(1.03×10^-9) (P = 0.000