Conjugative plasmids are important drivers of bacterial evolution. Most plasmids lack genes for conjugation and characterized origins of transfer (oriT), which has hampered our understanding of plasmid mobility. Here we used bioinformatic analyses to characterize occurrences of known oriT families across 38,057 plasmids, confirming that most conjugative and mobilizable plasmids lack identifiable oriTs. Recognizable oriT sequences tend to be intergenic, upstream of relaxase genes and specifically associated with relaxase types. We used these criteria to develop a computational method to search for and identify 21 additional families of oriT-containing sequences in plasmids from the pathogens Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii. Sequence analyses found 3,072 occurrences of these oriT-containing sequences across 2,976 plasmids, many of which encoded antimicrobial resistance genes. Six candidate oriT-containing sequences were validated experimentally and were shown to facilitate conjugation in E. coli. These findings expand our understanding of plasmid mobility.

偶联质粒是细菌进化的重要驱动因素。大多数质粒缺乏结合基因和特征转移起点 （oriT），这阻碍了我们对质粒迁移率的理解。在这里，我们使用生物信息学分析来表征 38,057 个质粒中已知 oriT 家族的出现，证实大多数共轭和可动员质粒缺乏可识别的 oriTs。可识别的 oriT 序列往往是基因间的，位于松弛酶基因的上游，并且与松弛酶类型特别相关。我们使用这些标准开发了一种计算方法，以搜索和鉴定来自病原体大肠杆菌、肺炎克雷伯菌和鲍曼不动杆菌的质粒中另外 21 个含 oriT 序列家族。序列分析发现，在 2,976 个质粒中出现了 3,072 个这些含有 oriT 的序列，其中许多编码抗菌素耐药基因。6 个含有 oriT 的候选序列经过实验验证，并被证明可促进大肠杆菌中的偶联。这些发现扩展了我们对质粒迁移率的理解。