Kivisaar Maia
Department of Genetics, Institute of Molecular and Cell Biology, Tartu University and Estonian Biocentre, 51010 Tartu, Estonia.
Environ Microbiol. 2003 Oct;5(10):814-27. doi: 10.1046/j.1462-2920.2003.00488.x.
Microorganisms are exposed to constantly changing environmental conditions. In a growth-restricting environment (e.g. during starvation), mutants arise that are able to take over the population by a process known as stationary phase mutation. Genetic adaptation of a microbial population under environmental stress involves mechanisms that lead to an elevated mutation rate. Under stressful conditions, DNA synthesis may become more erroneous because of the induction of error-prone DNA polymerases, resulting in a situation in which DNA repair systems are unable to cope with increasing amounts of DNA lesions. Transposition may also increase genetic variation. One may ask whether the rate of mutation under stressful conditions is elevated as a result of malfunctioning of systems responsible for accuracy or are there specific mechanisms that regulate the rate of mutations under stress. Evidence for the presence of mutagenic pathways that have probably been evolved to control the mutation rate in a cell will be discussed.
微生物暴露于不断变化的环境条件中。在生长受限的环境中（例如饥饿期间），会出现能够通过一种称为稳定期突变的过程接管种群的突变体。环境压力下微生物种群的遗传适应涉及导致突变率升高的机制。在压力条件下，由于易错DNA聚合酶的诱导，DNA合成可能会变得更易出错，导致DNA修复系统无法应对不断增加的DNA损伤。转座也可能增加遗传变异。人们可能会问，压力条件下的突变率升高是由于负责准确性的系统故障导致的，还是存在特定机制来调节压力下的突变率。将讨论可能已经进化以控制细胞中突变率的诱变途径存在的证据。
