Targeting antibiotic resistance: the importance of genome segregation

细菌抗生素耐药性是世界范围内人类健康的主要威胁。耐多药“超级细菌”的出现要么是由于基因组内的突变，要么是由于存在于质粒等可移动遗传元件上的耐药基因的水平转移。负责抗生素耐药性的低拷贝数质粒采用复杂的策略来确保细胞分裂时的忠实分布。这些质粒编码两种蛋白质，一种三磷酸腺苷酶和一种DNA结合蛋白，它们组装成一个极简的DNA分离机器。这种蛋白质复合物与染色体相互作用，驱动质粒到达确定的亚细胞地址。当这个系统出现故障时，质粒丢失，导致对抗生素敏感的细菌群。我们的模型系统是一个多重耐药质粒，在大肠杆菌中复制。质粒编码两种蛋白质，这两种蛋白质形成一个复合物，负责在细胞中维持质粒。我们提出了一个维纳斯捕蝇器模型作为质粒分离的机制，该模型预测质粒被捕获在由其中一种蛋白质形成的三维笼状基质中。本项目将在单分子水平上研究分离蛋白的相互作用和复杂组装的动力学，采用多学科的前沿方法在物理-生物学界面上进行研究。

Bacterial antibiotic resistance is a major threat to human health worldwide. The emergence of multidrug-resistant 'superbugs' results either from mutations within the genome or from the horizontal transfer of resistance genes present on mobile genetic elements such as plasmids. Low-copy number plasmids responsible for antibiotic resistance employ sophisticated strategies to ensure faithful distribution at cell division. These plasmids encode two proteins, an ATPase and a DNA-binding protein, which assemble into a minimalist DNA segregation machine. This protein complex interacts with the chromosome and drives the plasmids to defined subcellular addresses. When this systems malfunctions, the plasmid is lost, resulting in an antibiotic-sensitive bacterial population. Our model system is a multidrug resistant plasmid, which replicates in Escherichia coli. The plasmid encodes two proteins that form a complex responsible for maintaining the plasmid in the cell. We proposed a Venus flytrap model as a mechanism for plasmid segregation, which predicts that the plasmid is captured within a three-dimensional cage-like matrix formed by one of the proteins. This project will investigate the interaction of the segregation proteins and the dynamics of complex assembly at single-molecule level, using multidisciplinary cutting-edge approaches at the physics-biology interface.