摘要
观察了野生型抗辐射菌ＤｅｉｎｏｃｏｃｕｓｒａｄｉｏｄｕｒａｎｓＫＤ８３０１及其修复缺陷突变体ＫＨ３１１１对γ射线的抗性程度，探讨了影响辐射抗性的有关因素。ＫＤ８３０１和ＫＨ３１１１经大剂量γ射线照射（０．５～１０ｋＧｙ），制作剂量－存活曲线；利用荧光分光光度法测定细胞的ＤＮＡ含量。结果表明，野生型的ＫＤ８３０１对射线具有显著抗性，推定的ＬＤ９９为９．５ｋＧｙ，而其突变体ＫＨ３１１１的抗性明显减弱，ＬＤ９９为２．４ｋＧｙ；指数生长期的ＫＤ８３０１对射线的抗性明显低于稳定期的，ＬＤ９９分别为５．２ｋＧｙ和９．５ｋＧｙ；指数生长期和稳定生长期细菌细胞内ＤＮＡ相对含量无明显差异，说明ＤＮＡ的相对含量与细菌的辐射抗性无密切关系，即辐射抗性的决定因素不是ＤＮＡ的相对含量，而是细菌所处的生长状态。
In this study, the radioresistance of wild type Deinococcus radiodurans KD8301 and the factors affecting the radioresistance were investigated. KH3111 which was a DNA repair mutant of KD8301 (Zeji Du, 1998) was used to be compared with KD8301. Deinococcus radiodurans was discovered by Anderson et al (1956) in X-ray sterilized canned meat that was found to have undergone spoilage. This bacterium and other species of this genus share extreme resistance to ionozing radiation and other agents that damage DNA. Wild type KD8301 and its sensitive mutant KH3111 were irradiated with 60 Coγ-ray at the dose range 0.5～10kGy. Dose-survival fraction curves were made and the radioresistances were determined by LD 99 . The relative contents of DNA in cells were measured by Fluorescence Spectrophotometry (Freedman and Bruce, 1971). The results indicated that wild type KD8301 possesses more radoresistant than its mutant KH3111, LD99 were 9.5kGy and 2.4kGy respectively. KD8301 grown at exponential phase showed a decreased resistance to radiation, and the LD99 was 5.1kGy. No differences of DNA/protein in cells were found between the exponential phase and the stationary phase. The results could be concluded that wild type KD8301 possesses remarkable radioresistance, but this ability was decreased or disappeared after mutation (in KH3111). None DNA relative content other than the growthstages were determinant factors of radioresistance in Deinococcus radiodurans . This results were different from other report(Dickie N et al , 1990).The cellular mechanisms might be the defferences of the bacterium cell morphology between the exponential phase and the stationary phase. Recently, the mutation site of KH3111 which was mutated chemically from wild type KD8301 was identified (Zeji Du, 1998). One base pair changed in the novel gene pprA which was isolated from KD8301 genomic DNA.This point mutation was confirmed to be responsable for the sensitivity of KH3111 to γ-ray and other DNA-damaging agents.
出处
《辐射研究与辐射工艺学报》
CAS
CSCD
北大核心
1999年第2期89-92,共4页
Journal of Radiation Research and Radiation Processing
基金
日本科学技术厅(STA)资助
