Studies on Etching and Damage Action of Low Energy Ion Beam on icrobial Cells

The action of 20 keV N(+) ion on Deinococcus radiodurans and E. coli was investigated by means of scanning electron microscope(SEM) and electron spin resonance(ESR). The results showed that ion implantation exerted direct etching damage and indirect free radicals action by energy deposition on the cells of the two microbes. The DNA damage and biological mutation resulted mainly from the etching action of injected ions; the free radicals resulted chiefly in the damage of peroxidation of biological macromolecule and membrane lipids except of DNA. Moreover, the damages in D. radiodurans and E. coli by etching and free radicals action aggravated gradually with increasing doses. The sedimentation patterns of tritiated DNA materials in D. radiodurans by neutral sucrose gradient(50-200 g/L) indicated that DNA sedimentation peak of cells incubated for 4 h did not resume control state after the implantation of 60x10(15) N(+) ions injection per cm(2), proving that the direct action of implanted ions led to DNA damage. The survival rate of the implanted D. radiodurans and E. coli lowered after 2 mol/L caffeine and 0.5 mmol/L EDTA treatment, confirming that the etching action of implanted ions was the direct cause resulting in DNA damage and organism mutation.