Escherichia coli and many other bacterial species, which are incapable of sporulation, can nevertheless survive within resource exhausted media by entering a state termed long-term stationary phase (LTSP). We have previously shown that E. coli populations adapt genetically under LTSP in an extremely convergent manner. Here, we examine how the dynamics of LTSP genetic adaptation are influenced by varying a single parameter of the experiment—culture volume. We find that culture volume affects survival under LTSP, with viable counts decreasing as volumes increase. Across all volumes, mutations accumulate with time, and the majority of mutations accumulated demonstrate signals of being adaptive. However, positive selection appears to affect mutation accumulation more strongly at higher, compared with lower volumes. Finally, we find that several similar genes are likely involved in adaptation across volumes. However, the specific mutations within these genes that contribute to adaptation can vary in a consistent manner. Combined, our results demonstrate how varying a single parameter of an evolutionary experiment can substantially influence the dynamics of observed adaptation.

中文翻译：

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培养体积影响长期静止阶段下的适应动态

大肠杆菌和许多其他无法形成孢子的细菌物种仍然可以通过进入称为长期固定相 (LTSP) 的状态在资源枯竭的培养基中存活。我们之前已经表明，大肠杆菌种群以极其收敛的方式在 LTSP 下进行遗传适应。在这里，我们研究了 LTSP 遗传适应的动态如何受到改变实验的单个参数 - 培养体积的影响。我们发现培养体积会影响 LTSP 下的存活率，随着体积的增加，活菌数会减少。在所有体积中，突变随时间累积，并且累积的大多数突变显示出适应性信号。然而，与较低体积相比，正选择似乎在较高体积时更强烈地影响突变积累。最后，我们发现几个相似的基因可能涉及跨体积的适应。然而，这些基因中有助于适应的特定突变可能以一致的方式变化。结合，