De Paepe Marianne, Taddei François
Laboratoire de Genetique Moleculaire, Evolutive et Medicale, University of Paris 5, INSERM, Paris, France.
PLoS Biol. 2006 Jul;4(7):e193. doi: 10.1371/journal.pbio.0040193.
Life history theory accounts for variations in many traits involved in the reproduction and survival of living organisms, by determining the constraints leading to trade-offs among these different traits. The main life history traits of phages-viruses that infect bacteria-are the multiplication rate in the host, the survivorship of virions in the external environment, and their mode of transmission. By comparing life history traits of 16 phages infecting the bacteria Escherichia coli, we show that their mortality rate is constant with time and positively [corrected] correlated to their multiplication rate in the bacterial host. Even though these viruses do not age, this result is in line with the trade-off between survival and reproduction previously observed in numerous aging organisms. Furthermore, a multiple regression shows that the combined effects of two physical parameters, namely, the capsid thickness and the density of the packaged genome, account for 82% of the variation in the mortality rate. The correlations between life history traits and physical characteristics of virions may provide a mechanistic explanation of this trade-off. The fact that this trade-off is present in this very simple biological situation suggests that it might be a fundamental property of evolving entities produced under constraints. Moreover, such a positive correlation between mortality and multiplication reveals an underexplored trade-off in host-parasite interactions.
生活史理论通过确定导致这些不同性状之间权衡的限制因素，解释了参与生物体繁殖和生存的许多性状的变化。噬菌体（即感染细菌的病毒）的主要生活史性状包括在宿主中的增殖速率、病毒粒子在外部环境中的存活率及其传播方式。通过比较16种感染大肠杆菌的噬菌体的生活史性状，我们发现它们的死亡率随时间恒定，且与它们在细菌宿主中的增殖速率呈正相关。尽管这些病毒不会衰老，但这一结果与之前在众多衰老生物体中观察到的生存与繁殖之间的权衡是一致的。此外，多元回归分析表明，衣壳厚度和包装基因组密度这两个物理参数的综合作用，解释了死亡率变化的82%。生活史性状与病毒粒子物理特征之间的相关性，可能为这种权衡提供了一个机制性解释。这种权衡存在于这种非常简单的生物学情境中，这一事实表明它可能是在限制条件下产生的进化实体的一个基本属性。此外，死亡率与增殖之间的这种正相关揭示了宿主-寄生虫相互作用中一个尚未充分探索的权衡。
