DinB基因的超表达短期内可显著降低大肠杆菌的死亡率

 目的]探讨大肠杆菌dinB基因在进化上的选择优势.方法]应用竞争共培养和超表达的策略,测定共培养后含dinB基因的目的菌株和对照菌株的生长优势.第1组为含质粒pUC-dinB-rrnb的E.coli AB1157＋含质粒pUC-dinBR-rrnb的E.coli YG7207;第2组为含质粒pUC-dinB-rrnb的E..coli AB1157＋含质粒pUC-phoE-rrnb的E.coli YG7207;第3组为含质粒pUC-phoE-rrnb的E.coli AB1157＋含质粒pUC-dinBR-rrnb的E.coli YG7207;第4组为卡那霉素抗性（K^＋）菌株YG7207与无卡那霉素抗性菌株AB1157.结果]第4组中,卡那霉素抗性菌株YG7207与无卡那霉素抗性菌株AB1157在培养物中的比例保持着良好的稳定.第1组和第2组混合培养中,K^＋抗性的菌株在培养物中的比例急剧下降,并很快接近或等于0;第3组培养物中,K^＋菌株（YG7207）的比例呈明显上升.结论]超表达dinB基因的大肠杆菌菌株的生长优势不是由于对数期的生长速率提高所造成,对数后期细胞死亡率降低应该是超表达dinB基因的大肠杆菌菌株的生长优势的主要原因.

Overexpression of dinB in E. coli Can Significantly Reduce Cell Death Rate

Objective] To study the biological significance and selection advantage of dinB gene in Escherichia coli. Methods] Determine the growth advantage of E.coli strains with and without dinB by using co-culture competition strategy. Group 1 was E.coli AB1157 with pUC-dinB-rrnb + E.coli YG7207 with pUC-dinBR-rrnb; Group 2 was E.coli AB1157 with pUC-dinB-rrnb + E.coli YG7207 with pUC-phoE-rrnb; Group 3 was E.coli AB1157 with pUC-phoE-rrnb + E.coli YG7207 with pUC-dinBR-rrnb; group 4 is YG7207 + AB1157. Result] In group 4, the proportion between YG7207 and AB1157 was maintained at a stable level. In Group 1 and Group 2, colonies of strain resistant against kalamycin reduced abruptly to 0. In Group 3, colonies of strain resistant against kalamycin increase significantly. Conclusion] The reduction in mortality during the stationary phase is the main reason leading to the growth advantage of dinB-overexpressing E. coli strains.