Aoki S, Ito S, Watanabe T
Microbiol Immunol. 1979;23(3):147-58. doi: 10.1111/j.1348-0421.1979.tb00451.x.
The inactivation by ultraviolet (UV) light irradiation of mycoplasma cells of five human strains was monitored by investigating the colony-forming ability. The survival curves of five strains tested indicated that the cells of Mycoplasma buccale only are single and homogenously susceptible to UV light. The effect of the repair inhibitor, caffeine, on the colony-forming ability of UV-irradiated cells was investigated with M. buccale because of its homogenous susceptibility to UV light. The colony formation of irradiated cells was markedly depressed by post-irradiation treatment with caffeine at concentrations that had little or no effect on the colony formation of unirradiated cells. The colony-forming units (CFU) of UV-irradiated cells which were kept in broth without caffeine in the dark increased without a lag as the time in the dark increased. The colony-forming ability of the irradiated cells completely recovered after 3 hr in the dark. However, when irradiated cells were kept in the presence of caffeine, no increase in their CFU was observed. The mode of action of caffeine on UV-irradiated cells closely resembles that described for other organisms which possess dark reactivation systems for UV-induced damage in deoxyribonucleic acid (DNA). Thus, the results obtained provide evidence for the existence of a dark repair function in M. buccale.
通过研究集落形成能力，监测了紫外线（UV）照射对五株人支原体细胞的灭活作用。所测试的五株支原体的存活曲线表明，只有颊支原体细胞对紫外线单一且均匀敏感。由于颊支原体对紫外线具有均匀敏感性，因此研究了修复抑制剂咖啡因对紫外线照射细胞集落形成能力的影响。在对未照射细胞的集落形成几乎没有影响或没有影响的浓度下，用咖啡因进行照射后处理可显著抑制照射细胞的集落形成。在黑暗中保存在不含咖啡因的肉汤中的紫外线照射细胞的集落形成单位（CFU）随着在黑暗中的时间增加而无延迟地增加。照射细胞在黑暗中3小时后集落形成能力完全恢复。然而，当照射细胞保存在咖啡因存在的情况下，未观察到其CFU增加。咖啡因对紫外线照射细胞的作用方式与其他具有针对紫外线诱导的脱氧核糖核酸（DNA）损伤的暗修复系统的生物体所描述的作用方式非常相似。因此，所获得的结果为颊支原体中存在暗修复功能提供了证据。
