1Experimental evolution of microbes often involves a serial transfer protocol with repeated dilutions and transfers to 2 fresh media to start a new growth cycle. Here we study how in silico evolved Virtual Microbe "wild types" (WTs) 3 adapt to such a protocol, study the generic evolutionary features, and investigate how these features depend on prior 4 evolution. All WTs adopt a balance of growth and survival, therewith anticipating the regularity of the serial 5 transfer. We find that this anticipation can happen by means of a single lineage, or by coexisting lineages that 6 specialise on either the growth phase or the stationary phase. Parallel experiments of the same WT show similar 7 trajectories with respect to growth and yield, and similar biases towards diversification. In summary, all our in silico 8 WTs show the same anticipation effects -fitting the periodicity of serial transfer protocol -but prior adaptations 9 determines what solution is found by subsequent evolution. 10 15 adapt to such a simple protocol, we might one day be able to predict evolution in the lab and -ideally -also in 16 nature. Indeed, a lot of evolution in the lab seems remarkably reproducible, where microbes show parallel adaptations 17 both on the level of the phenotype as well as the genotype [4][5][6][7][8][9][10][11]. However, there also seems to be strong potential 18 for divergent evolution, leading to diversity both between and within replicate populations [12][13][14]. Diversification 19 events within populations often entail cross-feeding interactions [12, 13,[15][16][17][18], where species emerge that grow on 20 metabolic by-products. These cross-feeding interactions are increasingly well understood with the help of metabolic 21 modeling and digital evolution [19, 20]. A recent metagenomic study has revealed even more coexisting lineages in the 22 LTEE than were previously reported [21]. It is however not yet clear whether all these polymorphisms are the result 23 of uni-directional cross-feeding interactions, or if other mechanisms could drive coexistence in a simple experiment 24 such as a serial transfer protocol.
25Prior to being subjected to lab conditions, the microbes used in the aforementioned experimental studies all 26 evolved for billions of years in natural environments, experiencing harshly fluctuating and -more often than not -27 unfavorable conditions. While a serial transfer protocol such as that of the LTEE at a first glance selects mostly for 28 higher growth rates when resources are abundant (i.e. during the log phase), there is also selection to survive when 29 resources are depleted and the population no longer grows (i.e. during the stationary phase). In fact, given the 30 1/31 unpredictable conditions found in nature, some of the ancestors of Escherichia coli might have survived precisely 31 because they diverted resources away from growth. Indeed, E. coli does exactly this during the stationary phase by 32 means of the stringent response, regulating up to one third of all genes during starvation [2...