Such a survival ratio curve was different from that of ion beam implantation, which exhibited a “saddle shape” demonstrated that the survival curve of B. subtilis Bs916 which was exposed to various doses of ion beam implantation, firstly decreased then slightly increased in the range of doses from 15 (2.6 1014 ions/cm2) to 25 (2.6 1014 ions/cm2) and finally decreased.