The F pilus serves as a conduit for the DNA during conjugation between physically distant bacteria.

Abstract

Horizontal transfer of F-like plasmids by bacterial conjugation is responsible for disseminating antibiotic resistance and virulence determinants among pathogenic Enterobacteriaceae species, a growing health concern worldwide. Central to this process is the conjugative F pilus, a long extracellular filamentous polymer that extends from the surface of plasmid donor cells, allowing it to probe the environment and make contact with the recipient cell. It is well established that the F pilus can retract to bring mating pair cells in tight contact before DNA transfer. However, whether DNA transfer can occur through the extended pilus has been a subject of active debate. In this study, we use live-cell microscopy to show that while most transfer events occur between cells in direct contact, the F pilus can indeed serve as a conduit for the DNA during transfer between physically distant cells. Our findings enable us to propose a unique model for conjugation that revises our understanding of the DNA transfer mechanism and the dissemination of drug resistance and virulence genes within complex bacterial communities.