Deoxyribonucleic acid strand breaks during freeze-drying and their repair in Escherichia coli

Abstract

Freeze-drying of Escherichia coli cells caused strand breaks of deoxyribonucleic acid (DNA) in both radiation-sensitive and -resistant strains. However, in the radiation-resistant strain E. coli B/r the damaged DNA was repaired after rehydration, whereas in the radiation-sensitive strain E. coli Bs-1 the damaged DNA was not repaired and the DNA was degraded. Repeated freeze-drying did not break the damaged DNA into smaller pieces.

Evidence of membrane damage in Lactobacillus bulgaricus following freeze drying

“…Examples of chemical markers include sodium chloride for cell membrane damage (Ray 1993), chloramphenicol for protein synthesis (Sogin and Ordal 1967), rifampicin for ribosome damage (Johnson et al 1984), actinomycin D for ribosome damage (Hurwitz et 01. 1962) and pyronin Y for DNA damage (Onishi et al 1977 ;Asada et al 1980). Early experiments confirmed the conclusions of Lievense et al (1994).…”

Deoxyribonucleic acid strand breaks during drying of Escherichia coli on a hydorohobic filter membrane

“…There are only a few reports on this problem. Ashwood-Smith and Grant (3) and Ohnishi et al (17) showed that freeze-drying caused DNA strand breaks in E. coli. Even by freezing, which is usually accompanied by dehydration of cells, single-strand breakage of DNA has been reported in E. coli (1,23) and Salmonella typhimurium (24).…”

Induction of mutation in Escherichia coli by freeze-drying

“…On the other hand, when E. coli NG 30 was freeze-dried for 2 to 4 h, the induced mutation frequency was less than 10-', indicating that no significant mutation occurred. Longer treatment of the cells (8 to 24 h) gave very low survival (0.0007% or less) as reported previously (10,15,16); thus reliable figures of the induced mutation frequency could not be obtained.…”

“…We have previously studied a possible mechanism for the low survival rates due to freeze-drying by using radioresistant strains, Escherichia coli B/r (uvr' exr+) and H/r 30R (uvrr exre), and radiosensitive strains, E. coli B..1 (uvrB exr) and NG 30 (recA), and found that freeze-drying caused strand breaks of chromosomal deoxyribonucleic acid (DNA) in both radiosensitive and -resistant strains (10,(14)(15)(16). Damaged DNA was repaired after rehydration in the radioresistant strains E. coli B/r and H/r 30R, whereas the damaged DNA was not repaired in the radiosensitive strains, E. coli B.-, and NG 30 (10,15). Degradation of damaged DNA in the radiosensitive strains after rehydration resulted in the death of the bacteria (10,15).…”

“…Damaged DNA was repaired after rehydration in the radioresistant strains E. coli B/r and H/r 30R, whereas the damaged DNA was not repaired in the radiosensitive strains, E. coli B.-, and NG 30 (10,15). Degradation of damaged DNA in the radiosensitive strains after rehydration resulted in the death of the bacteria (10,15). These findings have raised a serious question as to whether or not mutation is induced in the surviving cells during the repair of the damaged DNA.…”