Mutational spectrum of the lacI gene in Escherichia coli K12 induced by low-energy ion beam.
The mutational spectrum of the genomic lacI gene induced by low-energy nitrogen ion irradiation in wild type Escherichia coli strain W3110 were compared with the spontaneous and the vacuum controls. The mutant frequency of irradiated group was dose-dependent and reached 26.3 x 10(-6) at dose of 31.2 x 10(14) ions/cm2, which was about 18-fold over the background (1.5 x 10(-6)) and 10-fold over the vacuum controls (2.6 x 10(-6)). This result indicated that the low-energy ion irradiation was one of many effective mutagens, though the vacuum condition of low-energy ions contributed some low-level gene mutations. It was found that the difference between the spontaneous and the vacuum control was the increases of base-pair substitutions in the vacuum control group. The spectra of irradiated group were quite similar to that of oxygen free-radical induced in the same strain, suggesting free-radicals and other adducts generated by low-energy ions might play an important role in the mutagenesis in vivo. When the spontaneous and the vacuum control group were compared, base-pair substitutions, deletions and additions of the irradiated group were significantly increased, and the +TGGC or -TGGC at hot spot was decreased from 82 to 48%. But the remarkable increase in absolute MF of the +TGGC or -TGGC at hot spot in the irradiated group suggested that low-energy ions did induce the mutations of this type. The spectra of our irradiated group had relative low-level base-pair substitutions, high-level +/-TGGC and high proportion additions than those of gamma-radiation induced, implying there were some different effects or processes between them.
Tang
Ming Li
ML
Key Laboratory of Ion Beam Bioengineering, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, PR China.
Wang
Shun Chang
SC
Wang
Tao
T
Zhao
Shi Guang
SG
Wu
Yao Jing
YJ
Wu
Li Jun
LJ
Yu
Zeng Liang
ZL
D001426:Bacterial Proteins / Q000235:genetics*; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D048168:Escherichia coli K12 / Q000235:genetics / Q000528:radiation effects*; D029968:Escherichia coli Proteins; D005609:Free Radicals / Q000378:metabolism; D056968:Lac Repressors; D009154:Mutation; D011839:Radiation, Ionizing; D012097:Repressor Proteins / Q000235:genetics*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005609:Free Radicals; D056968:Lac Repressors; C539064:LacI protein, E coli; D012097:Repressor Proteins