Divergent adaptation of Escherichia coli to cyclic ultraviolet light exposures
Divergent adaptation of Escherichia coli to cyclic ultraviolet light exposures
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DOI：
10.1093/mutage/geh039
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发表时间：
2004-09-01
期刊：
影响因子：
2.7
通讯作者：
Serment-Guerrero, J
中科院分区：
文献类型：
--
作者：
Alcántara-Díaz, D;Breña-Valle, M;Serment-Guerrero, J
适应性进化过程中发生的遗传变化在进化生物学中特别有趣。作为适应性进化的结果，生物体的自然群体在选择性条件下在经过几代之后在遗传和表型上发生变化，以便在特定环境中生存。当DNA损伤和诱变剂（如紫外线）被实验用作选择因子时，细菌对该剂的天然抵抗力通常会通过突变和选择过程而增强。由于紫外线诱导的诱变并不限于特定的染色体区域，因此循环紫外线照射的结果同样可能会进化出不同的紫外线抵抗机制。然而，也有可能作为选择过程的结果，优先选择一种抗紫外线机制，导致不同细菌培养物的适应性趋同。如果最丰富或致命的 DNA 损伤优先由特定的 DNA 修复途径甚至特定的修复酶控制，或者降低细菌适应性的耐药机制倾向于从群体中消除，则可能会发生这种情况。为了检查这两种替代方案中哪一种实际发生，对 5 种大肠杆菌培养物进行了 80 个连续紫外线照射周期的并行处理。最后，这五种培养物产生了不同程度的抗紫外线能力，经过初步表征后，我们发现对循环紫外线照射的适应是选择与 DNA 修复和复制相关的不同基因中出现的有利突变的结果。
The genetic changes taking place during adaptive evolution are particularly interesting in evolutionary biology. As a consequence of adaptive evolution, natural populations of an organism under selective conditions change genetically and phenotypically after a number of generations in order to survive in that particular environment. When a DNA-damaging and mutagenic agent like UV light is experimentally used as a selective factor, natural resistance of bacteria to this agent is normally increased through processes of mutation and selection. Since UV-induced mutagenesis is not restricted to particular chromosomal regions, different UV resistance mechanisms will equally probably evolve as a consequence of cyclic UV irradiation. However, it is also possible that as a consequence of the selective process, one UV resistance mechanism is preferentially selected, causing adaptive convergence of different bacterial cultures. This may occur if the most abundant or lethal kind of DNA lesion is preferentially managed by a particular DNA repair pathway and even by a specific repair enzyme or if resistance mechanisms that decrease bacterial fitness tend to be eliminated from the populations. To examine which of these two alternatives actually takes place, five cultures of Escherichia coli were treated in parallel for 80 successive UV irradiation cycles. At the end, these five cultures gave rise to different grades of UV resistance and after a preliminary characterization we found that adaptation to cyclic UV irradiation was a consequence of selection of advantageous mutations arising in different genes related to repair and replication of DNA.