The two major spore DNA repair pathways, nucleotide excision repair and spore photoproduct lyase, are sufficient for the resistance of Bacillus subtilis spores to artificial UV-C and UV-B but not to solar radiation.
The two major spore DNA repair pathways, nucleotide excision repair and spore photoproduct lyase, are sufficient for the resistance of Bacillus subtilis spores to artificial UV-C and UV-B but not to solar radiation.
复制标题
两种主要的孢子 DNA 修复途径，即核苷酸切除修复和孢子光产物裂合酶，足以使枯草芽孢杆菌孢子抵抗人工 UV-C 和 UV-B，但不足以抵抗太阳辐射。
DOI：
10.1128/aem.62.7.2221-2227.1996
复制
发表时间：
1996
影响因子：
4.4
通讯作者：
Nicholson,WL
中科院分区：
文献类型：
--
作者：
Xue,Y;Nicholson,WL
细菌内生孢子对254-nm UV（UV-C）辐射的抗性比相同菌株的指数生长细胞高1至2个数量级。这种高紫外线抗性是由于两个相关的现象：（i）用254 nm紫外线照射的休眠孢子的DNA主要积累一种独特的胸腺嘧啶二聚体，称为孢子光产物（SP），和（ii）SP在孢子萌发过程中通过两种主要的DNA修复途径，核苷酸切除修复（NER）和SP特异性酶称为SP裂解酶进行校正。迄今为止，人们一直认为这两个因素也是环境中细菌孢子对太阳紫外线的抵抗力，尽管地球表面的阳光由UV-B，UV-A，可见光和红外波长约290 nm和更长的波长组成。为了检验这一假设，测定了缺乏NER或SP裂解酶DNA修复途径的枯草芽孢杆菌的等基因菌株对许多UV波长的辐射的相对抗性，包括UV-C（254 nm）、UV-B（290至320 nm）、全光谱日光和去除了UV-B部分的日光。为了直接比较的目的，相对于由野生型孢子和缺乏两种DNA修复系统的孢子的混合物组成的经校准的生物剂量计来确定孢子UV抗性水平。据观察，两种途径对孢子UV抗性的相对贡献取决于所用的UV波长而改变，其方式表明用环境相关UV波长的光照射的孢子除了SP之外还可以积累大量的一种或多种DNA光产物。此外，注意到在暴露于增加的波长时，野生型孢子的抗紫外线能力从33倍（UV-C）下降到12倍（UV-B + UV-A日光）至6倍（单独的UV-A阳光）比缺乏两种DNA修复系统的突变体更具抗性，这表明在增加太阳紫外线波长时，孢子被NER或SP裂解酶系统不能修复的DNA损伤、对除DNA以外的光敏分子造成的损伤或两者灭活。
Bacterial endospores are 1 to 2 orders of magnitude more resistant to 254-nm UV (UV-C) radiation than are exponentially growing cells of the same strain. This high UV resistance is due to two related phenomena: (i) DNA of dormant spores irradiated with 254-nm UV accumulates mainly a unique thymine dimer called the spore photoproduct (SP), and (ii) SP is corrected during spore germination by two major DNA repair pathways, nucleotide excision repair (NER) and an SP-specific enzyme called SP lyase. To date, it has been assumed that these two factors also account for resistance of bacterial spores to solar UV in the environment, despite the fact that sunlight at the Earth's surface consists of UV-B, UV-A, visible, and infrared wavelengths of approximately 290 nm and longer. To test this assumption, isogenic strains of Bacillus subtilis lacking either the NER or SP lyase DNA repair pathway were assayed for their relative resistance to radiation at a number of UV wavelengths, including UV-C (254 nm), UV-B (290 to 320 nm), full-spectrum sunlight, and sunlight from which the UV-B portion had been removed. For purposes of direct comparison, spore UV resistance levels were determined with respect to a calibrated biological dosimeter consisting of a mixture of wild-type spores and spores lacking both DNA repair systems. It was observed that the relative contributions of the two pathways to spore UV resistance change depending on the UV wavelengths used in a manner suggesting that spores irradiated with light at environmentally relevant UV wavelengths may accumulate significant amounts of one or more DNA photoproducts in addition to SP. Furthermore, it was noted that upon exposure to increasing wavelengths, wild-type spores decreased in their UV resistance from 33-fold (UV-C) to 12-fold (UV-B plus UV-A sunlight) to 6-fold (UV-A sunlight alone) more resistant than mutants lacking both DNA repair systems, suggesting that at increasing solar UV wavelengths, spores are inactivated either by DNA damage not reparable by the NER or SP lyase system, damage caused to photosensitive molecules other than DNA, or both.