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Abstract
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OBJECTIVE To determine the effect of cheA gene of Helicobacter pylori in the bacterial chemotaxis in vitro and colonization in vivo.
METHODS The entire cheA and cheY genes were amplified and cloned from genomic DNA of H. pylori NCTC11637 strain. Subsequently, the prokaryotic expression systems of cheA and cheY genes were generated and the target recombinant proteins rCheA and rCheY were extracted by Ni-NTA affinity chromatography. Rabbits were immunized with either rCheA or rCheY for obtaining antisera, and rCheA-IgG and rCheY-IgG in the antisera were prepared using ammonium sulfate precipitation plus DEAE-52 column chromatography. A suicide plasmid of cheA gene was constructed and then a cheA gene knock-out mutant ( cheA - ) was generated based on homologous recombinant exchange using the suicide plasmid. The cheA- mutant was identified using PCR and sequencing. The phosphorylation levels of CheA and CheY molecules of cheA - and wild-type strain were determined by using rCheA-IgG and rCheY-IgG anchoring the target proteins and protein phosphorylation detection kit. The differences of chemotaxis in vitro and colonization in vivo between cheA- mutant and wild-type strain were compared using chemotactic model and BALB/c infection model of H. pylori.
RESULTS The cheA gene knock-out in genome of cheA- mutant was confirmed by the results of PCR and sequencing. After treated with 0. 001-0. 1 mol/L HCI for 10 min, the phosphorylation levels of CheA and CheY molecules of wild-type strain were rapidly descended from ( 59.6 ±11.5) μmol and (55.5 ± 10.2) μmol to ( 10.8 ± 2.6) and (5. 5 ± 1.2) μmol (P ＜ 0.05 ), while the phosphorylation of CheY molecule of cheA - mutant was no markedly changed with a persistent lower level ( P ＞0.05). The diameters [(10-20) ± (2-3) mm] of chemotactic aggregative rings of cheA- mutant were significantly less than those [(16-24) ± (2-3)mm] of wild-type strain (P ＜0.05). The positive isolation rate (90%) of H. pylori in gastric biopsy specimens of mice that infected with wild-type strain was remarkably higher than that (40%) of mice that infected with cheA- mutant (P ＜0.05). The result of fluorescence quantitative was also showed that the numbers (6.3 × 103 ±2.1 × 103 copies/mg) of H. pylori in gastric biopsy specimens of wild-type strain infected mice were significantly larger than those (8.3 × 101 ±3. 1 × 101 copies/mg) in gastric biopsy specimens ofcheA- mutant infected mice (P＜0.05).
CONCLUSION The cheA gene of H. pylori has an important role in the bacterial chemotaxis in vitro and colonization in vivo.
Language: zh |