Spatial refuges and nutrient acquisition predict the outcome of evolutionary rescue in evolving microbial populations
Spatial refuges and nutrient acquisition predict the outcome of evolutionary rescue in evolving microbial populations
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DOI：
10.1101/2023.11.21.568097
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发表时间：
2023-11
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影响因子：
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通讯作者：
Matthew Kelbrick;Andy Fenton;S. Parratt;James P. J. Hall;Siobhán O’Brien
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作者：
Matthew Kelbrick;Andy Fenton;S. Parratt;James P. J. Hall;Siobhán O’Brien
微生物种群经常暴露于影响其生存和进化的环境压力。生态进化理论表明，微生物种群可能能够通过“空间避难所”在压力源中生存下来，低应力或应力降低的区域，例如生物膜内。然而，空间避难所减少了人口对营养物质的获取，因此可能是有害的，这取决于他们所躲避的压力的严重程度。使用来自一般数学模型的预测，以及细菌荧光假单胞菌SBW 25在盐度胁迫和不同机会下形成空间避难所（即，激动或非激动的文化条件），我们表明，空间避难所可以拯救人口的压力，只有当营养水平高。在存活的高盐度进化群体中（即，非搅拌的培养条件和高营养），克隆具有增加的耐盐性，表明空间避难所可以促进进化拯救。虽然全基因组重测序没有发现与耐盐性相关的单一特异性突变，但我们发现在控制条件（低盐，高营养，无搅拌）下进化的克隆获得了推定趋化基因的突变，并显示出增加的运动性。这表明，高盐度下的空间避难所也可能限制其他环境因素的适应。总之，我们的理论，实验室实验和基因组重新测序的结合证明了空间避难所在减轻微生物种群内的环境压力方面的价值和局限性。
Microbial populations are often exposed to environmental stressors that impact their survival and evolution. Eco-evolutionary theory suggests microbial populations may be able to survive a stressor through “spatial refuges” – i.e., areas of low or reduced stress such as within biofilms. However, spatial refuges reduce a population’s access to nutrients, so may be detrimental depending on the severity of the stressor they are sheltering from. Using predictions from a general mathematical model, and the experimental evolution of the bacterium Pseudomonas fluorescens SBW25 under salinity stress and varying opportunities to form spatial refuges (i.e., agitated or non-agitated culture conditions), we show that spatial refuges can rescue a population from stressors only when nutrient levels are high. In the surviving high-salinity evolved populations (i.e., non-agitated culture conditions and high-nutrients), clones had an increased salinity resistance, indicating that spatial refuges can facilitate evolutionary rescue. Though whole genome resequencing did not reveal a single specific mutation associated with salt resistance, we found that clones evolved under control conditions (lower salt, high-nutrients, and no agitation) acquired mutations in a putative chemotaxis gene and showed increased motility. This indicates that spatial refuges under high salinity may also constrain adaptations to other environmental factors. Together, our combination of theory, laboratory experiment, and genome re-sequencing demonstrate the value and limits of spatial refuges in alleviating environmental stress within microbial populations.