Bacteria from natural populations transfer plasmids mostly towards their kin

Plasmids play a key role in microbial ecology and evolution, yet the determinants of plasmid transfer rates are poorly understood. Particularly, interactions between donor hosts and potential recipients are understudied. Here we investigate the importance of genetic similarity between naturally co-occurring Escherichia coli isolates in plasmid transfer. We uncover extensive variability, spanning over five orders of magnitude, in the ability of isolates to donate and receive two different plasmids, R1 and RP4. Overall, transfer is strongly biased towards clone-mates, but not correlated to genetic distance when donors and recipients are not clone-mates. Transfer is limited by the presence of a functional restriction-modification system in recipients, suggesting sharing of strain-specific defence systems contributes to bias towards kin. Such restriction of transfer to kin sets the stage for longer-term coevolutionary interactions leading to mutualism between plasmids and bacterial hosts in...

质粒在微生物生态学与演化中发挥关键作用，但目前学界对质粒转移速率的决定因素仍知之甚少。尤为突出的是，供体宿主与潜在受体间的互作关系尚未得到充分研究。本研究聚焦自然共存的大肠杆菌（Escherichia coli）分离株之间的遗传相似性对质粒转移的影响。我们发现，分离株对两种不同质粒R1与RP4的供体及受体能力存在广泛变异，变异幅度跨越五个数量级。总体而言，质粒转移强烈偏向克隆株，但当供体与受体并非克隆株时，转移效率与遗传距离并无显著相关性。受体若携带功能性限制性修饰系统（restriction-modification system），则会限制质粒转移，这表明菌株特异性防御系统的共享是转移偏向亲缘菌株的重要原因。这种将转移限制于亲缘菌株的现象，为长期协同进化互作奠定了基础，进而促使质粒与细菌宿主之间形成互利共生关系……