Cell-free study of F plasmid partition provides evidence for cargo transport by a diffusion-ratchet mechanism

ParA-type partition systems self-organize and pattern the bacterial nucleoid to organize plasmids, chromosomes, and protein machinery spatially. To study how protein patterns generate cargo movement, we reconstituted and visualized the partition system of F plasmid using a DNA-carpeted flowcell as an artificial nucleoid surface. We found that the partition proteins could bridge plasmid to the DNA carpet dynamically and mediate plasmid motion. Our data favor a diffusion-ratchet mechanism inherently different from classical motor protein or actin/microtubule filament-based transport. We expect surface-mediated patterning to become increasingly recognized as a means of intracellular transport in all kingdoms of life.