4. Induction of Mutation by Drying in Bacteria and Effects of Thiourea, Adonitol and Cysteine on Prevention of Induction of Mutation(Lectures presented at the Meeting on the 30th Anniversary of Japanese Society for Research of Freezing and Drying(in part))

Abstract

Preservation of cells by L-drying or freeze-drying caused induction of mutation in Escherichia coli. The induction depended on the temperature during preservation. When the dried cells were preserved at temperature between 10℃ and 48℃, the number of mutants in the surviving fraction increased as the storage temperature increased. The induction of mutation could be detected neither in the cells rehydrated immediately after drying nor in the dried cells preserved at temperature below 5℃. Thiourea, adonitol and cysteine were found to be effective against the cause of mutation, which reduced the frequency of mutation during preservation. These compounds improved survival and/or prevented the induction of mutation by adding into a fluid for drying, even when the dried cells were preserved at high temperature. It seems that the roles of thiourea and adonitol in protecting the cells from mutation are to prevent DNA-strand breakage by acting as radical-scavengers during preservation of dried cells, and that of cysteine is to stimulate the activity of DNA-repair system after rehydration of dried cells and/or to act protecting on the DNA-repair system enzyme(s) during preservation of dried cells.