Anticipation of a serial transfer protocol through the evolution of fine-tuned growth dynamics

Abstract

BackgroundExperimental evolution of microbes often involves a serial transfer protocol, where microbes are repeatedly diluted by transfer to a fresh medium, starting a new growth cycle. This protocol has revealed that evolution can be remarkably reproducible, where microbes show parallel adaptations both on the level of the phenotype as well as the genotype. However, these studies also reveal a strong potential for divergent evolution, leading to diversity both between and within replicate populations. We here study how in silico evolved Virtual Microbe "wild types" (WTs) adapt to a serial transfer protocol to investigate both the generic evolutionary adaptation to such an environment which are independent of prior evolution, and the variety of ways in which the adaptation is implemented at the individual and ecosystem level. ResultsWe show that all pre-evolved WTs evolve to anticipate the regularity of the serial transfer protocol by adopting a fine-tuned balance of growth and survival. We find that this anticipation can be done in a variety of ways, either by a single lineage or by several lineages in consort. Interestingly, replicate populations of the same WT initially show similar trajectories, but may subsequently diverge along a growth rate versus yield trade-off. ConclusionsWe find that all our in silico WTs show the same anticipation effects -- fitting the periodicity of a serial transfer protocol -- but do so by a variety of mechanisms. Our results reveal new insights into the dynamics and relevant selection pressures in experimental evolution, but also highlight how, in an eco-evolutionary context, numerous mechanisms can evolve to the same end.