3. Compounds Protecting L-Dried Cultures from Mutation (II) : Prevention of DNA Strand Breakage in L-Dried Escherichia coil by Thiourea, Adonitol and Cysteine(Synopsis paper presented at The 30th Annual Meeting)

Abstract

DNA injury in L-dried Escherichia coli cells was investigated using the alkaline sucrose gradient sedimentation technique. When the cells were dried in 0.1 M potassium phosphate buffer containing 3 % monosodium glutamate, no DNA single-strand breaks were detected immediately after drying, but temperature-dependent DNA breakage were induced during the preservation process in dried cells. Addition of 30mM thiourea or 100mM adonitol into the suspending fluid resulted no significant DNA breaks immediately after drying and after preservation for 6 months at 5℃. After preservation for 8 weeks at 37℃, DNA breaks in cells dried with thiourea or adonitol were apparently smaller as compared with those in cells dried without the protectants. Furthermore, thiourea and adonitol were protected vegetative cells from damage by radicals derived from hydrogen peroxide. From the results, thiourea and adonitol are considered to act as radical-scavenger, and resultant prevention of DNA strand breakage. No evidence for preventing effect of cysteine on DNA strand breakage has been obtained, and role of cysteine in increasing survival of dried cells has not been clear.