抗辐射菌lexA基因对受γ射线照射和MMC作用的大肠杆菌敏感性的影响

研究抗辐射菌lexA基因在大肠杆菌细胞中的表达对其γ射线辐射抗性和丝裂霉素(MMC)敏感性的影响。应用电穿孔技术将携带有抗辐射菌lexA基因的重组质粒PZA172转入大肠杆菌JM109，其启动子为lacZ，用异丙基-硫代-β—D半乳糖苷(IPTG)诱导，(十二烷基磺酸纳)聚炳烯酰胺凝胶电泳(SDS-PAGE)凝胶电泳检测LexA蛋白的表达。经受不同剂量γ射线照射和不同浓度的MMC作用，平板菌落计数，绘制存活曲线。抗辐射菌lexA基因在大肠杆菌细胞中，经IPTG诱导能稳定地表达，lexA基因的显著表达降低了大肠杆菌经γ射线照射和MMC作用后的存活率。抗辐射菌lexA基因在大肠杆菌中的显著表达降低了大肠杆菌对γ射线和MMC的抗性，其作用机理还有待于进一步的研究。

Effect of the lexA gene of deinococcus radiodurans on the resistance of escherichia coli to γ-rays and MMC

The work is to study the effect of lexA gene of Deinococcus radiodurans expressed in Escherichia coli on its resistance to y-rays and MMC. Recombinant plasmid pZA172 was constructed by cloning the lexA gene of Deinococcus radiodurans into the vector plasmid PUC 19 in the downstream of lacZ promoter. Transfected Escherichia coli strain JM109(pZA172) was obtained through transfection of JM109 strain with pZA172 by electropo-ration. Expression of the lexA protein in the IPTG-INDUCED JM109 (Pzal72) was checked by SDS-PAGE, and survival curve of the strain was measured using colony formation assay after treatment with different doses of radiation and different concentrations of MMC. After IPTG induction, the lexA protein was significantly expressed in the strain JM109 (pZA172), and the survival rate of the strain was higher than that of the control. The expression of Deinococcus radiodurans lexA gene in Escherichia coli resulted in the increase of sensitivity of the latter to y-rays and MMC. Mechanism of the effect remains to be further investigated.