Low-energy (30 keV) carbon ion induced mutation spectrum in the LacZ alpha gene of M13 mp 18 double-stranded DNA

Double-stranded M13 mp 18 DNA was irradiated with 30 ke V carbon ions in dry state under vacuum to investigate the low-energy heavy ion induced mutation spectra. When the irradiated DNA was used to transfect Escherichia coli JM 105, 3.6-5.7-fold increases in mutation frequency were observed, in contrast to the spontaneous group. Sequences of the 92 induced mutants showed that the carbon ions in this study could induce an interesting mutation spectrum in the lacZ alpha gene. One-base mutations (96.8%) and base pair substitutions (56.4%) were predominant, most of which involved G:C base pairs (90.6%), especially G:C --> T:A transversions (49.6%) and G:C --> A:T transitions (39.6%). This is similar to the spectra induced by gamma-rays in the same ds M13, wild type E. coli system. We also found a considerable amount of carbon ion induced one-base deletion (38.5%) and the mutation sites distribution on the target lacZ alpha gene was obviously non-random. We compared this study with previous data employing gamma-rays to discuss the possible causes of the mutation spectrum.