Aoki K, Furusawa M
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan.
J Theor Biol. 2001 Mar 21;209(2):213-22. doi: 10.1006/jtbi.2000.2257.
The efficient evolution of a population requires both genetic diversity and stable reproduction of advantageous genotypes. The accuracy of DNA replication guarantees the stable reproduction, while errors during DNA replication produce the genetic diversity. Thus, one key to the promotion of evolution is inherent in DNA replication. In bacteria, replication forks progress bidirectionally from the single origin of replication on a genome. One replication fork contains two DNA polymerase molecules so that four DNA polymerases simultaneously carry out the replication of a genome. It is generally believed that the fidelity of the intracellular DNA polymerases is identical (parity strategy). To test this, we examined the effects of the intracellular coexistence of a mutator polymerase with low fidelity and a normal polymerase with high fidelity on adaptive evolution (disparity strategy). From the analysis using genetic algorithms based on the bacterial replication, it was found that the population using the disparity strategy could further expand its genetic diversity and preserve the advantageous genotypes more profoundly than the parity population. This strongly suggests that bacteria replicating with a disparity strategy may undergo rapid evolution, particularly during severe environmental changes. The implications of the conspicuous adaptability of Escherichia coli mutator strains are discussed in this context.
种群的有效进化既需要遗传多样性，也需要优势基因型的稳定繁殖。DNA复制的准确性保证了稳定繁殖，而DNA复制过程中的错误则产生了遗传多样性。因此，促进进化的一个关键就在于DNA复制本身。在细菌中，复制叉从基因组上的单一复制起点双向推进。一个复制叉包含两个DNA聚合酶分子，这样四个DNA聚合酶同时进行基因组的复制。人们通常认为细胞内DNA聚合酶的保真度是相同的（均等策略）。为了验证这一点，我们研究了低保真度的突变聚合酶与高保真度的正常聚合酶在细胞内共存对适应性进化的影响（差异策略）。通过基于细菌复制的遗传算法分析发现，采用差异策略的种群比采用均等策略的种群能够进一步扩大其遗传多样性，并更深入地保留优势基因型。这有力地表明，采用差异策略进行复制的细菌可能会经历快速进化，尤其是在剧烈的环境变化期间。在此背景下讨论了大肠杆菌突变菌株显著适应性的意义。
