Departament de Fisica Fonamental, Facultat de Fisica, Universitat de Barcelona, Barcelona, Spain.
PLoS One. 2011 Apr 15;6(4):e18622. doi: 10.1371/journal.pone.0018622.
Bacteria spend most of their lifetime in non-growing states which allow them to survive extended periods of stress and starvation. When environments improve, they must quickly resume growth to maximize their share of limited nutrients. Cells with higher stress resistance often survive longer stress durations at the cost of needing more time to resume growth, a strong disadvantage in competitive environments. Here we analyze the basis of optimal strategies that microorganisms can use to cope with this tradeoff. We explicitly show that the prototypical inverse relation between stress resistance and growth rate can explain much of the different types of behavior observed in stressed microbial populations. Using analytical mathematical methods, we determine the environmental parameters that decide whether cells should remain vegetative upon stress exposure, downregulate their metabolism to an intermediate optimum level, or become dormant. We find that cell-cell variability, or intercellular noise, is consistently beneficial in the presence of extreme environmental fluctuations, and that it provides an efficient population-level mechanism for adaption in a deteriorating environment. Our results reveal key novel aspects of responsive phenotype switching and its role as an adaptive strategy in changing environments.
细菌在大部分时间处于非生长状态，这使它们能够在长时间的压力和饥饿中存活下来。当环境改善时，它们必须迅速恢复生长，以最大限度地利用有限的营养物质。具有更高抗压力的细胞通常能在更长的压力持续时间内存活，但代价是需要更多的时间来恢复生长，这在竞争环境中是一个很大的劣势。在这里，我们分析了微生物可以用来应对这种权衡的最佳策略的基础。我们明确表明，抗压力和生长速度之间的典型反比关系可以解释在受压力的微生物群体中观察到的许多不同类型的行为。使用分析数学方法，我们确定了决定细胞在受到压力时是应该保持营养生长、下调代谢至中间最佳水平还是进入休眠状态的环境参数。我们发现，细胞间的变异性或细胞间噪声在环境剧烈波动的情况下始终是有益的，并且它为在恶化的环境中进行适应性进化提供了一种有效的群体水平机制。我们的研究结果揭示了响应表型转换的关键新方面及其在变化环境中作为适应性策略的作用。
