Multidrug resistance (MDR) often results from the acquisition of mobile genetic elements (MGEs) that encode MDR gene(s), such as conjugative plasmids. The spread of MDR plasmids is founded on their ability of horizontal transference, as well as their faithful inheritance in progeny cells. Here, we investigated the genetic factors involved in the prevalence of the IncI conjugative plasmid pESBL, which was isolated from the Escherichia coli O104:H4 outbreak strain in Germany in 2011. Using transposon-insertion sequencing, we identified the pESBL partitioning locus (par). Genetic, biochemical and microscopic approaches allowed pESBL to be characterized as a new member of the Type Ib partitioning system. Inactivation of par caused mis-segregation of pESBL followed by post-segregational killing (PSK), resulting in a great fitness disadvantage but apparent plasmid stability in the population of viable cells. We constructed a variety of pESBL derivatives with different combinations of mutations in par, conjugational transfer (oriT) and pnd toxin-antitoxin (TA) genes. Only the triple mutant exhibited plasmid-free cells in viable cell populations. Time-lapse tracking of plasmid dynamics in microfluidics indicated that inactivation of pnd improved the survival of plasmid-free cells and allowed oriT-dependent re-acquisition of the plasmid. Altogether, the three factors—active partitioning, toxin-antitoxin and conjugational transfer—are all involved in the prevalence of pESBL in the E. coli population.

中文翻译：

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来自大肠杆菌 O104:H4 的 ESBL 质粒的垂直和水平传播

多药耐药性 (MDR) 通常源于获得编码 MDR 基因的移动遗传元件 (MGE)，例如接合质粒。MDR 质粒的传播建立在它们的水平转移能力以及它们在后代细胞中的忠实遗传基础上。在这里，我们调查了与 IncI 接合质粒 pESBL 流行有关的遗传因素，该质粒于 2011 年从德国大肠杆菌 O104:H4 爆发株中分离出来。使用转座子插入测序，我们确定了 pESBL 分区位点 (par) . 遗传、生化和显微方法使 pESBL 被定性为 Ib 型分区系统的新成员。par 的失活导致 pESBL 的错误分离，然后是分离后杀死 (PSK)，导致很大的适应性劣势，但在活细胞群中明显的质粒稳定性。我们构建了多种 pESBL 衍生物，在 par、接合转移 (oriT) 和 pnd 毒素-抗毒素 (TA) 基因中具有不同的突变组合。只有三重突变体在活细胞群中表现出无质粒细胞。微流体中质粒动力学的延时跟踪表明 pnd 的失活提高了无质粒细胞的存活率，并允许依赖于 oriT 的质粒重新获取。总之，三个因素——主动分配、毒素-抗毒素和结合转移——都与大肠杆菌群体中 pESBL 的流行有关。接合转移 (oriT) 和 pnd 毒素-抗毒素 (TA) 基因。只有三重突变体在活细胞群中表现出无质粒细胞。微流体中质粒动力学的延时跟踪表明 pnd 的失活提高了无质粒细胞的存活率，并允许依赖于 oriT 的质粒重新获取。总之，三个因素——主动分配、毒素-抗毒素和结合转移——都与大肠杆菌群体中 pESBL 的流行有关。接合转移 (oriT) 和 pnd 毒素-抗毒素 (TA) 基因。只有三重突变体在活细胞群中表现出无质粒细胞。微流体中质粒动力学的延时跟踪表明 pnd 的失活提高了无质粒细胞的存活率，并允许依赖于 oriT 的质粒重新获取。总之，三个因素——主动分配、毒素-抗毒素和结合转移——都与大肠杆菌群体中 pESBL 的流行有关。