Escherichia coli populations in unpredictably fluctuating environments evolve to face novel stresses through enhanced efflux activity
Escherichia coli populations in unpredictably fluctuating environments evolve to face novel stresses through enhanced efflux activity
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DOI：
10.1111/jeb.12640
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发表时间：
2015-05-01
影响因子：
2.1
通讯作者：
Dey, S.
中科院分区：
文献类型：
--
作者：
Karve, S. M.;Daniel, S.;Dey, S.
有相当多的理解实验室人口如何应对可预测的（恒定或恶化的环境）选择单一的环境变量，如温度或pH值。然而，这样的见解可能不适用时，选择环境包括多个变量，波动不可预测的，是常见的性质。为了解决这个问题，我们在营养肉汤中培养了重复的实验室大肠杆菌种群，营养肉汤的pH值和盐（NaCl）和过氧化氢（H2O2）的浓度每天随机变化。经过近似170代的选择，在三种选择环境中，选择群体的适合度都没有增加。然而，这些选定的人口有显着更大的适应性在四个新的环境，没有已知的适应性相关的耐受pH值，NaCl或H2O2。有趣的是，与预期相反，超变基因并没有进化。相反，被选中的种群进化出了能量依赖性外排活动的能力，这可能使它们能够以更快的速度从细胞中排出毒素，包括抗生素。这为细菌的进化性如何进化提供了一种替代机制，并可能导致广谱抗生素耐药性，即使在没有先前抗生素暴露的情况下。鉴于环境变异性在本质上正在增加，这可能会对公共健康产生严重后果。
There is considerable understanding about how laboratory populations respond to predictable (constant or deteriorating environment) selection for single environmental variables such as temperature or pH. However, such insights may not apply when selection environments comprise multiple variables that fluctuate unpredictably, as is common in nature. To address this issue, we grew replicate laboratory populations of Escherichia coli in nutrient broth whose pH and concentrations of salt (NaCl) and hydrogen peroxide (H2O2) were randomly changed daily. After similar to 170 generations, the fitness of the selected populations had not increased in any of the three selection environments. However, these selected populations had significantly greater fitness in four novel environments which have no known fitness-correlation with tolerance to pH, NaCl or H2O2. Interestingly, contrary to expectations, hypermutators did not evolve. Instead, the selected populations evolved an increased ability for energy-dependent efflux activity that might enable them to throw out toxins, including antibiotics, from the cell at a faster rate. This provides an alternate mechanism for how evolvability can evolve in bacteria and potentially lead to broad-spectrum antibiotic resistance, even in the absence of prior antibiotic exposure. Given that environmental variability is increasing in nature, this might have serious consequences for public health.