“Saddle-shaped” dose-survival effect, is it a general and valuable phenomenon in microbes in response to heavy ion beam irradiation?

Abstract

We aimed to verify the “saddle-shaped” dose-survival effect of microbes in response to heavy ion beam irradiation (HI), and further determine the radiation parameter that affects saddle shape formation, and the relationship between the saddle region and the positive mutation rate. A bibliometric analysis was performed based on literature containing the dose-survival effect of microbes in response to HI, from which the data on the particle energies, ionic types, irradiated microbes, survival curves, and maximum positive mutation rates were assembled. Articles reporting a “saddle-shaped” survival curve accounted for 64% of the total relevant articles and possessed a high cited frequency. The predominant articles, authors, and institutions that reported the dose-survival effect of microbes in response to HI proposed the “saddle-shaped” survival curve. It was customarily low-energy (but not moderate- or high-energy) HI that induced the “saddle-shaped” dose-survival effect. In addition, the “saddle-shaped” dose-survival effect was general among ~ 30-genera microbes. More importantly, most of the saddle regions contained the survival fractions within 10–30%, which are customarily used to screen mutants due to a high positive mutation rate. Further, 87% of the maximum positive mutation rates were associated with the saddle region, and 58% were located in the peak of the saddle region. “Saddle-shaped” dose-survival effect is a reliable and general phenomenon among varieties of microbes customarily in response to low-energy HI. Meanwhile, saddle region is always accompanied with high positive mutation rates. Thus, this study will aid in microbial mutation breeding practices.