Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel.
Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot 7610001, Israel.
Cell Rep. 2018 Jun 5;23(10):2891-2900. doi: 10.1016/j.celrep.2018.05.007.
Bacterial growth follows simple laws in constant conditions. However, bacteria in nature often face fluctuating environments. We therefore ask whether there are growth laws that apply to changing environments. We derive a law for upshifts using an optimal resource-allocation model: the post-shift growth rate equals the geometrical mean of the pre-shift growth rate and the growth rate on saturating carbon. We test this using chemostat and batch culture experiments, as well as previous data from several species. The increase in growth rate after an upshift indicates that ribosomes have spare capacity (SC). We demonstrate theoretically that SC has the cost of slow steady-state growth but is beneficial after an upshift because it prevents large overshoots in intracellular metabolites and allows rapid response to change. We also provide predictions for downshifts. The present study quantifies the optimal degree of SC, which rises the slower the growth rate, and suggests that SC can be precisely regulated.
在恒定条件下，细菌生长遵循简单的规律。然而，自然界中的细菌经常面临波动的环境。因此，我们要问是否有适用于变化环境的生长规律。我们使用最优资源分配模型推导出适用于上移的规律：上移后的生长速率等于上移前的生长速率和饱和碳上的生长速率的几何平均值。我们使用恒化器和分批培养实验以及来自多个物种的先前数据来测试这一点。上移后的生长速率增加表明核糖体有备用容量 (SC)。我们从理论上证明，SC 的代价是稳态生长缓慢，但在上移后是有益的，因为它可以防止细胞内代谢物的大幅超调，并允许对变化做出快速响应。我们还提供了下移的预测。本研究定量了最佳的 SC 程度，其随生长速率的降低而增加，并表明 SC 可以精确调节。
