Amelioration of the Fitness Costs of Antibiotic Resistance Due To Reduced Outer Membrane Permeability by Upregulation of Alternative Porins
Amelioration of the Fitness Costs of Antibiotic Resistance Due To Reduced Outer Membrane Permeability by Upregulation of Alternative Porins
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DOI：
10.1093/molbev/msv195
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发表时间：
2015-12-01
影响因子：
10.7
通讯作者：
Andersson, Dan I.
中科院分区：
文献类型：
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作者：
Knopp, Michael;Andersson, Dan I.
抗生素耐药性的适应度成本是决定耐药细菌进化成功的关键参数。抗生素耐药性对细菌适应性影响的研究严重偏向于靶点改变。在这里，我们调查了如何在一个严重受损的生长速度与阻力，由于缺乏两个主要的外膜孔蛋白的形式的成本可以遗传补偿。我们进行了一个进化实验与16个血统的大肠杆菌的双突变体与ompCF基因删除，并减少健身和增加耐药性不同类别的抗生素，包括碳青霉烯类，厄他培南和美罗培南。仅连续传代250代后，相对生长率从0.85增加到0.99（易感野生型设定为1.0）。成本补偿遵循两种不同的适应性途径，其中替代性孔蛋白表达的上调绕过了对功能性OmpCF孔蛋白的需要。第一种补偿机制涉及phoR和pstS基因的突变，导致组成型高水平表达的PhoE孔蛋白。第二种机制涉及hfq和chiX基因的突变，这些突变破坏了Hfq依赖的小RNA调控，导致ChiP孔蛋白的过度表达。虽然敏感性恢复补偿突变体与PhoE过表达，进化突变体与高芯片表达保持耐药表型。我们的研究结果可以解释为什么孔蛋白的组成经常改变耐药的临床分离株，并提供新的见解如何旁路机制可能允许遗传适应一个共同的多药耐药机制。
The fitness cost of antibiotic resistance is a key parameter in determining the evolutionary success of resistant bacteria. Studies of the effect of antibiotic resistance on bacterial fitness are heavily biased toward target alterations. Here we investigated how the costs in the form of a severely impaired growth rate associated with resistance due to absence of two major outer membrane porins can be genetically compensated. We performed an evolution experiment with 16 lineages of a double mutant of Escherichia coli with the ompCF genes deleted, and reduced fitness and increased resistance to different classes of antibiotics, including the carbapenems ertapenem and meropenem. After serial passage for only 250 generations, the relative growth rate increased from 0.85 to 0.99 (susceptible wild type set to 1.0). Compensation of the costs followed two different adaptive pathways where upregulation of expression of alternative porins bypassed the need for functional OmpCF porins. The first compensatory mechanism involved mutations in the phoR and pstS genes, causing constitutive high-level expression of the PhoE porin. The second mechanism involved mutations in the hfq and chiX genes that disrupted Hfq-dependent small RNA regulation, causing overexpression of the ChiP porin. Although susceptibility was restored in compensated mutants with PhoE overexpression, evolved mutants with high ChiP expression maintained the resistance phenotype. Our findings may explain why porin composition is often altered in resistant clinical isolates and provide new insights into how bypass mechanisms may allow genetic adaptation to a common multidrug resistance mechanism.