Extremely fast amelioration of plasmid fitness costs by multiple functionally diverse pathways
Extremely fast amelioration of plasmid fitness costs by multiple functionally diverse pathways
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DOI：
10.1099/mic.0.000862
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发表时间：
2020-01-01
期刊：
影响因子：
2.8
通讯作者：
Brockhurst, Michael A.
中科院分区：
文献类型：
--
作者：
Hall, James P. J.;Wright, Rosanna C. T.;Brockhurst, Michael A.
质粒的获得通常伴随着适应性成本，因此需要补偿进化来允许质粒生存，但尚不清楚补偿进化是否足够广泛或足够快以在成本非常昂贵时维持质粒。耐汞质粒 pQBR55 在获得后立即显着降低了其宿主荧光假单胞菌 SBW25 的生长，导致了小菌落表型。然而，在琼脂平板上生长 48 小时内，我们观察到祖先大菌落形态的恢复，表明补偿性突变已经发生。这些进化菌株在实验室培养基和土壤微观世界中的相对适应性在重复之间存在差异，表明不同的突变机制。通过基因组测序，我们发现恢复与假设的 DNA 结合蛋白 PFLU4242、RNA 聚合酶或 GacA/S 双组分系统中的染色体突变有关。 PFLU4242、gacA 或 gacS 中的靶向删除重现了质粒获得后改善的表型，表明了三种不同的补偿突变途径。我们的数据表明，质粒补偿进化足够快，足以允许质粒存活，尽管它对其宿主施加了非常高的适应性成本，并且实际上可能在分离和选择单个含有质粒的克隆的过程中经常发生。
The acquisition of plasmids is often accompanied by fitness costs such that compensatory evolution is required to allow plasmid survival, but it is unclear whether compensatory evolution can be extensive or rapid enough to maintain plasmids when they are very costly. The mercury-resistance plasmid pQBR55 drastically reduced the growth of its host, Pseudomonas fluorescens SBW25, immediately after acquisition, causing a small colony phenotype. However, within 48h of growth on agar plates we observed restoration of the ancestral large colony morphology, suggesting that compensatory mutations had occurred. Relative fitness of these evolved strains, in lab media and in soil microcosms, varied between replicates, indicating different mutational mechanisms. Using genome sequencing we identified that restoration was associated with chromosomal mutations in either a hypothetical DNA-binding protein PFLU4242, RNA polymerase or the GacA/S two-component system. Targeted deletions in PFLU4242, gacA or gacS recapitulated the ameliorated phenotype upon plasmid acquisition, indicating three distinct mutational pathways to compensation. Our data shows that plasmid compensatory evolution is fast enough to allow survival of a plasmid despite it imposing very high fitness costs upon its host, and indeed may regularly occur during the process of isolating and selecting individual plasmid-containing clones.