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），且这些胁迫往往会发生不可预测的波动。尽管学界已分别针对单一胁迫与环境波动这两类因素开展研究，但二者的交互作用仍鲜有探索。为填补这一研究空白，我们将大肠杆菌（Escherichia coli）的实验室种群置于由pH、过氧化氢（H₂O₂）与氯化钠（NaCl）组成的复合胁迫环境中，且该环境的胁迫水平发生不可预测的波动，连续传代约900代。我们将该经胁迫波动筛选的种群的生长速率及其适应性权衡模式，与在相同传代时长内、仅施加单一恒定胁迫组分的筛选种群进行了对比。经胁迫波动筛选的种群，在所有经历的筛选环境中，平均生长速率更高，且生长速率的变异程度更低。然而，仅在恒定胁迫下筛选的种群，会在非其所处的筛选环境中表现出适应性权衡；而经胁迫波动筛选的种群则几乎完全规避了跨环境适应性权衡。值得注意的是，研究还发现生长速率与环境容纳量之间存在适应性权衡。本研究结果表明，环境的复杂性与胁迫波动，会显著影响进化种群的内在适应性权衡结构。