Effect Of Rare Earth On The8-OHdG Of Bacillus Subtilis

As long as wide use of rare earth makes more and more attention has been paid to itssafety problem. The former studies in our group showed that rare earth can damage theDNA of organism through oxidation process.8-hydroxy-2`deoxyguanosine （8-OHdG） isone of the products of deoxyribonucleoside hydroxylation, which can reflects the degree ofDNA oxidative injury. The purposes of this research is to study the effect of rare earth onB.subtilis in cellular level through measuring the content of8-OHdG, and to explore theeffect of rare earth on DNA in gene molecular level by measuring the content of8-OHdGwhen rare earth directly affects calf thymus DNA and the changes in the structure of dGand four bases （A, T, C and G）.The content of8-OHdG in B.subtilis culture, intracellular and DNA molecules aredetected by HPLC-UV. The structure change of dG and four bases are measured by theultraviolet spectrum method and the viscosity method.When the concentration of Nd³⁺, Gd³⁺and La³⁺is1×10-3mol/L, all of them can inhibitthe growth of bacteria. The8-OHdG content in DNA hydrolyzate will increase when theconcentration of Nd³⁺、Gd³⁺and La³⁺are below the inhibit concentration at the startingtime. However, after adding the three ions for12hours, the content of8-OHdG decreased.The experimental results show that the response of the bacterial cells on rare earth atdifferent stages of growth is different. The rare earth has the oxidative damage to DNAwhen the cells at initial growth stage, while the rare earth reduced oxidative damage whenthe cells entered the logarithmic growth phase in12hours.The experimental results show that Nd³⁺, Gd³⁺and La³⁺directly affect the ctDNAdirectly and the three kinds of rare earth have obvious effect on the content of8-OHdG andguanine in DNA molecules. The content of8-OHdG and guanine are related to theconcentration of rare earth. The content of8-OHdG and guanine are decrease with theconcentration of rare earth increase. The rare earth and H2O2have synergistic effect. Nd³⁺,Gd³⁺and La³⁺can affect the molecular structure of four bases （A, T, C and G）, and theeffect becomes more obvious with the concentration of the rare earth increase. Accordingto the literature at home and abroad and the results of our group, we can surmise that therare earth ions can be combined to DNA in non-insertion way, then reduce the content of8-OHdG, guanine, dG and the four bases. In addition, the H2O2can promote the effect of rare earth on DNA and dG.The rare earth showing the inhibition and dose-effect on the growing of bacterial cells,which means the rare earth have oxidative damage on the cells. And the rare earth even canaffect the structures of DNA molecule, dG and bases. Therefore, these results haveimportant significance on the biological effects and biological safety of rare earth in futurestudy.