PDF(Pubmed)
Abstract：
Large cointegrate plasmids recruit genetic features of their parental plasmids and serve as important vectors in the spread of antibiotic resistance. They are now frequently found in clinical settings, raising the issue of how to limit their further transmission. Here, we conducted evolutionary research of a large blaNDM-positive cointegrate within Escherichia coli C600, and discovered that adaptive evolution of chromosome and plasmid jointly improved bacterial fitness, which was manifested as enhanced survival ability for in vivo and in vitro pairwise competition, biofilm formation, and gut colonization ability. From the plasmid aspect, large-scale DNA fragment loss is observed in an evolved clone. Although the evolved plasmid imposes a negligible fitness cost on host bacteria, its conjugation frequency is greatly reduced, and the deficiency of anti-SOS gene psiB is found responsible for the impaired horizontal transferability rather than the reduced fitness cost. These findings unveil an evolutionary strategy in which the plasmid horizontal transferability and fitness cost are balanced. From the chromosome perspective, all evolved clones exhibit parallel mutations in the transcriptional regulatory stringent starvation Protein A gene sspA. Through a sspA knockout mutant, transcriptome analysis, in vitro transcriptional activity assay, RT-qPCR, motility test, and scanning electron microscopy techniques, we demonstrated that the mutation in sspA reduces its transcriptional inhibitory capacity, thereby improving bacterial fitness, biofilm formation ability, and gut colonization ability by promoting bacterial flagella synthesis. These findings expand our knowledge of how cointegrate plasmids adapt to new bacterial hosts.
摘要：
大型共整合质粒招募其亲本质粒的遗传特征，并在抗生素抗性的传播中充当重要的载体。它们现在经常在临床环境中被发现，提出了如何限制它们进一步传播的问题。这里,我们在大肠杆菌C600内进行了大量blaNDM阳性共整合的进化研究，发现染色体和质粒的适应性进化共同改善了细菌的适应性，表现为体内和体外成对竞争的生存能力增强，生物膜的形成，和肠道定植能力。从质粒方面,在进化的克隆中观察到大规模的DNA片段丢失。尽管进化的质粒对宿主细菌的适应性成本可以忽略不计，它的共轭频率大大降低，发现抗SOS基因psiB的缺乏是导致水平转移性受损的原因，而不是降低的健身成本。这些发现揭示了一种进化策略，其中质粒水平可转移性和适应性成本得到平衡。从染色体的角度来看,所有进化的克隆都在转录调节严格饥饿蛋白A基因sspA中表现出平行突变。通过一个sspA敲除突变体,转录组分析，体外转录活性测定，RT-qPCR,运动性试验,和扫描电子显微镜技术，我们证明了sspA中的突变降低了其转录抑制能力，从而改善细菌适应性，生物膜形成能力，和肠道定植能力通过促进细菌鞭毛合成。这些发现扩大了我们对共整合质粒如何适应新细菌宿主的认识。
