Lotareva O V, Filippov V D
Genetika. 1992 Jun;28(6):22-8.
The frequency of leu----Leu+ reversions represented mainly by suppressor mutations is increased in Bacillus subtilis uvr+ and uvr-1 cells after exposure to natural sunlight. Dependence of mutation yield on the time of exposure is linear (one hit kinetics) in case of the uvr-1 strain. In the uvr+ cells the yield of mutations is also linear, but only at short times of exposure, the curve bending and levelling off the plateau after 10-min cell illumination. It has been established in the experiments with optical filters that the mutagenic effect is related to wavelengths which correspond to the UVB zone of ecological UV. The mutagenesis caused by sunlight can be modified (weakened) by some post-irradiation treatments of bacteria, which also led to a decrease of mutations frequencies in B. subtilis uvr+ and uvr-1 cells after exposure to 254-nm UV. The data indicate that: 1) mutagenic influence of sunlight can be overcome only by the joint action of activities of the two cellular repair systems--photoreactivation and excision repair, 2) the real mutagenic effect of sunlight on such a non-photoreactivating organism as B. subtilis would not be enhanced with the increase of the UVB flow in sunlight spectrum.
在暴露于自然阳光后，枯草芽孢杆菌uvr⁺和uvr⁻1细胞中以抑制基因突变为主的亮氨酸（Leu）----亮氨酸（Leu）⁺回复突变频率增加。对于uvr⁻1菌株，突变率对暴露时间的依赖性呈线性（单 hit 动力学）。在uvr⁺细胞中，突变率也是线性的，但仅在短时间暴露时如此，在细胞照射10分钟后，曲线弯曲并趋于平稳。通过光学滤光片实验已确定，诱变效应与对应于生态紫外线UVB区的波长有关。阳光引起的诱变作用可通过细菌的一些照射后处理进行改变（减弱），这也导致枯草芽孢杆菌uvr⁺和uvr⁻1细胞在暴露于254纳米紫外线后突变频率降低。数据表明：1）只有通过细胞的两种修复系统——光复活和切除修复的联合作用，才能克服阳光的诱变影响；2）随着阳光光谱中UVB流量的增加，阳光对枯草芽孢杆菌这种非光复活生物的实际诱变作用不会增强。
