School of Biological Sciences, The University of Queensland, , Brisbane, Queensland 4072, Australia, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, , Zurich 8092, Switzerland.
Proc Biol Sci. 2013 Nov 27;281(1775):20132609. doi: 10.1098/rspb.2013.2609. Print 2014 Jan 22.
Natural transformation is a process whereby bacteria actively take up DNA from the surrounding environment and incorporate it into their genome. Natural transformation is widespread in bacteria, but its evolutionary significance is still debated. Here, we hypothesize that transformation may confer a fitness advantage in changing environments through a process we term 'genetic time travel': by taking up old genes that were retained in the environment, the bacteria may revert to a past genotypic state that proves advantageous in the present or a future environment. We scrutinize our hypothesis by means of a mathematical model involving two bacterial types (transforming and non-transforming), a single locus under natural selection and a free DNA pool. The two bacterial types were competed in environments with changing selection regimes. We demonstrate that for a wide range of parameter values for the DNA turnover rate, the transformation rate and the frequency of environmental change, the transforming type outcompetes the non-transforming type. We discuss the empirical plausibility of our hypothesis, as well as its relationship to other hypotheses for the evolution of transformation in bacteria and sex more generally, speculating that 'genetic time travel' may also be relevant in eukaryotes that undergo horizontal gene transfer.
自然转化是一种细菌主动从周围环境中摄取 DNA 并将其整合到基因组中的过程。自然转化在细菌中广泛存在，但它的进化意义仍存在争议。在这里，我们假设转化可能通过我们称之为“遗传时间旅行”的过程在不断变化的环境中赋予适应性优势：通过摄取环境中保留的旧基因，细菌可能会恢复到过去的基因型状态，这种状态在当前或未来的环境中是有利的。我们通过一个涉及两种细菌类型（转化和非转化）、一个自然选择下的单一基因座和一个游离 DNA 池的数学模型来仔细研究我们的假设。这两种细菌类型在具有不断变化的选择机制的环境中竞争。我们证明，对于 DNA 周转率、转化率和环境变化频率的广泛参数值，转化型比非转化型更具竞争力。我们讨论了我们假设的经验合理性，以及它与细菌和性进化中其他转化假说的关系，推测“遗传时间旅行”在经历水平基因转移的真核生物中也可能相关。
