Peninsula Medical School, Plymouth, PL6 8BU, United Kingdom.
Evolution. 2010 Feb 1;64(2):515-21. doi: 10.1111/j.1558-5646.2009.00821.x. Epub 2009 Aug 17.
Within-host competition between parasite genotypes can play an important role in the evolution of parasite virulence. For example, competition can increase virulence by imposing selection for parasites that replicate at a faster absolute rate within the host, but may also decrease virulence by selecting for faster relative growth rates through social exploitation of conspecifics. For many parasites, both outcomes are possible. We investigated how competition affected the evolution of virulence of the opportunistic pathogen Pseudomonas aeruginosa in caterpillar hosts, over the course of an approximately 60 generation selection experiment. We initiated infections with clonal populations of either wild-type bacteria or an isogenic mutant with an approximately 100-fold higher mutation rate, resulting in low and high between-genotype competition, respectively. We observed the evolution of increased virulence, growth rate, and public goods cheating (exploitation of extracellular iron scavenging siderophores produced by ancestral populations) in mutator but not wild-type, populations. We conclude increases in absolute within-host growth rates appear to be more important than social cheating in driving virulence evolution in this experimental context.
寄生虫基因型之间的宿主内竞争在寄生虫毒力的进化中起着重要作用。例如，竞争可以通过选择在宿主内以更快的绝对速度复制的寄生虫来增加毒力，但也可以通过选择通过社会剥削同种个体的更快的相对生长率来降低毒力。对于许多寄生虫来说，这两种结果都是可能的。我们研究了在大约 60 代的选择实验中，机会性病原体铜绿假单胞菌在毛虫宿主中的竞争如何影响毒力的进化。我们用野生型细菌或突变率高约 100 倍的同源突变体的克隆种群引发感染，分别导致低和高的基因型间竞争。我们观察到在突变体而不是野生型种群中，毒力、生长率和公共物品欺骗（利用祖先种群产生的细胞外铁摄取铁载体）的进化增加了。我们的结论是，在这种实验环境中，绝对宿主内生长率的增加似乎比社会欺骗更能促进毒力的进化。
