European Centre for Environment and Human Health, University of Exeter Medical School, Environment and Sustainability Institute, Penryn Campus, TR10 9FE, UK.
Microbial Pharmacology and Population Biology Research Group, Department of Pharmacy, Faculty of Health Sciences, UiT - The Arctic University of Norway, Tromsø, Norway.
Microbiology (Reading). 2023 Aug;169(8). doi: 10.1099/mic.0.001375.
Natural transformation is a process where bacteria actively take up DNA from the environment and recombine it into their genome or reconvert it into extra-chromosomal genetic elements. The evolutionary benefits of transformation are still under debate. One main explanation is that foreign allele and gene uptake facilitates natural selection by increasing genetic variation, analogous to meiotic sex. However, previous experimental evolution studies comparing fitness gains of evolved transforming- and isogenic non-transforming strains have yielded mixed support for the 'sex hypothesis.' Previous studies testing the sex hypothesis for natural transformation have largely ignored species interactions, which theory predicts provide conditions favourable to sex. To test for the adaptive benefits of bacterial transformation, the naturally transformable wild-type and a transformation-deficient mutant were evolved for 5 weeks. To provide strong and potentially fluctuating selection, was embedded in a community of five other bacterial species. DNA from a pool of different strains was provided as a substrate for transformation. No effect of transformation ability on the fitness of evolved populations was found, with fitness increasing non-significantly in most treatments. Populations showed fitness improvement in their respective environments, with no apparent costs of adaptation to competing species. Despite the absence of fitness effects of transformation, wild-type populations evolved variable transformation frequencies that were slightly greater than their ancestor which potentially could be caused by genetic drift.
自然转化是一种细菌主动从环境中摄取 DNA 并将其重组到基因组中或重新转化为染色体外遗传元件的过程。转化的进化优势仍存在争议。一种主要的解释是，外来等位基因和基因的摄取通过增加遗传变异，类似于减数分裂性，从而促进自然选择。然而，以前比较进化转化和同源非转化菌株适应度增益的实验进化研究对“性假说”提供的支持不一。以前检验自然转化性假说的研究在很大程度上忽略了物种相互作用，理论预测这种相互作用提供了有利于性的条件。为了检验细菌转化的适应优势，对自然转化的野生型和转化缺陷突变体进行了 5 周的进化。为了提供强大且可能波动的选择，将 嵌入到其他五个细菌物种的群落中。作为转化底物，提供了来自不同 菌株的 DNA 池。没有发现转化能力对进化种群适应度的影响，大多数处理中适应度增加不显著。种群在各自的环境中表现出适应度的提高，对竞争物种的适应没有明显的代价。尽管转化没有适应度效应，但野生型种群进化出的转化频率具有可变的变化，略微高于其祖先，这可能是由遗传漂变引起的。
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