Tanaka Y, Yoh M, Takeda Y, Miwatani T
Appl Environ Microbiol. 1979 Mar;37(3):369-72. doi: 10.1128/aem.37.3.369-372.1979.
The effect of freeze-drying on phenotypic reversion of amino acid auxotrophy to prototrophy was studied in Escherichia coli. In a radioresistant strain, E. coli H/r 30 (uvr+ exr+), which can repair the deoxyribonucleic acid damaged due to freeze-drying, an increased mutation frequency from auxotrophy to prototrophy was observed with increased time of freeze-drying of the cells. On the other hand, in a radiosensitive strain, E. coli NG 30 (recA), which cannot repair the damaged deoxyribonucleic acid due to a lack of repair enzyme system, no significant reversion occurred, although the survival rate was very low. The rate of phenotypic reversion dut to freeze-drying in both E. coli RIMD 0509109 (uvr+ exr+) and RIMD 0509115 (uvr exr+) was almost the same, indicating that the phenomenon is independent of the uvr character. From these results it is concluded that mutation was induced in E. coli cells during the rehydration when the damaged deoxyribonucleic acid was repaired by exr character of the cells. Thus, we propose that a serious consideration should be paid to the freeze-drying technique to preserve bacterial cells.
在大肠杆菌中研究了冷冻干燥对氨基酸营养缺陷型向原养型表型回复的影响。在一种耐辐射菌株大肠杆菌H/r 30（uvr+ exr+）中，该菌株能够修复因冷冻干燥而受损的脱氧核糖核酸，随着细胞冷冻干燥时间的增加，观察到从营养缺陷型向原养型的突变频率增加。另一方面，在一种辐射敏感菌株大肠杆菌NG 30（recA）中，由于缺乏修复酶系统而无法修复受损的脱氧核糖核酸，尽管存活率非常低，但没有发生明显的回复。大肠杆菌RIMD 0509109（uvr+ exr+）和RIMD 0509115（uvr exr+）中因冷冻干燥导致的表型回复率几乎相同，表明该现象与uvr特性无关。从这些结果可以得出结论，当受损的脱氧核糖核酸通过细胞的exr特性进行修复时，在复水过程中大肠杆菌细胞发生了突变。因此，我们建议在保存细菌细胞时应认真考虑冷冻干燥技术。
