Department of Molecular Evolution, Centro de Astrobiología (CSIC-INTA), Ctra de Ajalvir, Km 4, 28850 Torrejón de Ardoz, Madrid, Spain.
Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain.
Sci Rep. 2018 May 24;8(1):8080. doi: 10.1038/s41598-018-26443-z.
Bacteriophages are the most numerous biological entities on Earth. They are on the basis of most ecosystems, regulating the diversity and abundance of bacterial populations and contributing to the nutrient and energy cycles. Bacteriophages have two well differentiated phases in their life cycle, one extracellular, in which they behave as inert particles, and other one inside their hosts, where they replicate to give rise to a progeny. In both phases they are exposed to environmental conditions that often act as selective pressures that limit both their survival in the environment and their ability to replicate, two fitness traits that frequently cannot be optimised simultaneously. In this study we have analysed the evolutionary ability of an RNA bacteriophage, the bacteriophage Qβ, when it is confronted with a temperature increase that affects both the extracellular and the intracellular media. Our results show that Qβ can optimise its survivability when exposed to short-term high temperature extracellular heat shocks, as well as its replicative ability at higher-than-optimal temperature. Mutations responsible for simultaneous adaptation were the same as those selected when adaptation to each condition proceeded separately, showing the absence of important trade-offs between survival and reproduction in this virus.
噬菌体是地球上数量最多的生物实体。它们是大多数生态系统的基础，调节着细菌种群的多样性和丰度，并为营养和能量循环做出贡献。噬菌体在其生命周期中有两个截然不同的阶段，一个是细胞外阶段，在这个阶段它们表现为惰性颗粒，另一个是在宿主内部阶段，在这个阶段它们复制产生后代。在这两个阶段，它们都暴露于环境条件下，这些条件经常作为选择压力，限制它们在环境中的生存能力和复制能力，这两个适应度特征往往不能同时优化。在这项研究中，我们分析了一种 RNA 噬菌体——Qβ 噬菌体在面临影响细胞外和细胞内介质的温度升高时的进化能力。我们的结果表明，Qβ 可以在暴露于短期高温细胞外热冲击时优化其生存能力，也可以在高于最佳温度时优化其复制能力。负责同时适应的突变与分别适应每种条件时选择的突变相同，表明在这种病毒中，生存和繁殖之间没有重要的权衡。
