Data from: Escherichia coli populations adapt to complex, unpredictable fluctuations by minimizing trade-offs across environments

In nature, organisms are simultaneously exposed to multiple stresses (i.e. complex environments) that often fluctuate unpredictably. Although both these factors have been studied in isolation, the interaction of the two remains poorly explored. To address this issue, we selected laboratory populations of Escherichia coli under complex (i.e. stressful combinations of pH, H2O2 and NaCl) unpredictably fluctuating environments for ~900 generations. We compared the growth rates and the corresponding trade-off patterns of these populations to those that were selected under constant values of the component stresses (i.e. pH, H2O2 and NaCl) for the same duration. The fluctuation-selected populations had greater mean growth rate and lower variation for growth rate over all the selection environments experienced. However, whereas the populations selected under constant stresses experienced trade-offs in the environments other than those in which they were selected, the fluctuation-selected populations could bypass the across-environment trade-offs almost entirely. Interestingly, trade-offs were found between growth rates and carrying capacities. The results suggest that complexity and fluctuations can strongly affect the underlying trade-off structure in evolving populations.

在自然环境中，生物体同时面临多种胁迫（即复杂环境），且这些胁迫往往呈现不可预测的波动。尽管学界已分别对这两类因素开展过研究，但二者的交互作用仍鲜有深入探索。为填补这一研究空白，我们将大肠杆菌（Escherichia coli）实验室种群置于由pH、过氧化氢（H₂O₂）和氯化钠（NaCl）组合构成的复合胁迫不可预测波动环境中，进行了约900代的传代筛选。我们将该筛选种群的生长速率及其对应的权衡模式，与在相同时长内、分别处于单一胁迫恒定条件（即pH、过氧化氢与氯化钠）下筛选的种群进行了对比。经波动胁迫筛选的种群，在所有经历的筛选环境中均表现出更高的平均生长速率，且生长速率的变异程度更低。然而，经恒定胁迫筛选的种群在非适配筛选环境中会出现生长权衡，而经波动胁迫筛选的种群则几乎完全规避了跨环境权衡现象。值得注意的是，研究还发现生长速率与环境容纳量（carrying capacity）之间存在权衡关系。研究结果表明，环境复杂性与胁迫波动可显著影响进化种群的内在权衡结构。