Abstract
A study was conducted to make L-dried cultures escape from mutation during preservation. Since lesion of chromosomal DNA caused by preservation Eof L-dried cells is origin of mutation, if the cells are dried and preserved under such conditions so that DNA might be free from damage, mutation would not be induced in the dried cells. Such conditions of drying could also considerably prevent decrease of the survival of dried cells in recA^- strain which lack a system of post-replication repair of damaged DNA. Under this idea, a method was elaborated for selecting compounds which, when added to suspending medium, increase the survival value of L-dried cells of Escherichia coli B/r recA^- as an indicator, and 59 various compounds were screened. Adonitol, AICA, cysteine, dithioerythritol, semicarbazide, sodium thioglycollate and thiourea were found to be remarkably effective and adenosine, cystine, cytidine, erythritol, glutathione, thiomalic acid, thymidine and urea to have weakly protective effect. In dried cells of recA^+ strains, adonitol, cysteine and thiourea not only increased survival value but also prevented induction of mutation. Especially thiourea completely precluded mutation at a concentration of 30 mM.
