不同利福平浓度压力下耐辐射球菌的自发突变率与突变谱研究

根据耐辐射球菌(Deinococcus radiodurans) rpoB基因的保守性，建立了rpoB/Rifr 突变分析系统。为研究不同利福平(rifampin, Rif)浓度对耐辐射球菌自发突变率和突变谱的影响，分别检测耐不同利福平浓度下辐射球菌的突变率。结果表明：在5μg/ml的利福平浓度下耐辐射球菌的突变率显著高于其在25和50μg/ml浓度下的突变率。随利福平浓度的不同而表现出的突变谱差异，表明在不同利福平浓度引起的活性自由氧(reactive oxygen species, ROS)压力下，耐辐射球菌可能使用不同抗突变的应对策略。在低利福平浓度下，耐辐射球菌重点修复碱基替换突变导致的DNA损伤。这可能是因为ROS的主要作用是导致DNA出现氧化性碱基损伤。

MUTATION RATE AND SPECTRUM OF SPONTANEOUS MUTATIONS OF Deinococcus radiodurans UNDER RIFAMPIN STRESS

An rpoB/Rifr mutation analysis system has been developed from D. radiodurans based on the conservation of rpoB gene. To investigate the concentration effect of rifampin on the spontaneous mutation rate and spectrum of D. radiodurans, the mutation frequencies and rates of D. radiodurans were measured under a wide concentration range of 5~ 50μg/ml of rifampin. It was found that the mutation rate of the bacterium in 5μg/ml of rifampin was significantly higher than those in 25 and 50μg/ml rifampin. Rifampin had concentration-denpendent effect not only on the mutation rate but also on the mutation spectrum. The different mutation spectrum under different concentration of rifampin suggested that D. radiodurans might change its anti-mutant strategy under reactive oxygen species (ROS) stress caused by low concentration of rifampin. It is speculated that D. radiodurans focuses on preventing base substitution mutation under low concentration of rifampin as ROS induces mainly oxidative base damage.