Encapsulated bacteria deform lipid vesicles into flagellated swimmers

TL;DR

This study demonstrates how encapsulated bacteria can deform lipid vesicles into motile, flagellated swimmers through physical coupling, offering insights into designing synthetic motile cells.

Contribution

It introduces a novel mechanism where bacteria inside vesicles induce motility by deforming membranes and coupling with flagella, advancing synthetic cell design.

Findings

Bacteria exert sufficient force to extrude membrane tubes.

Membrane tubes coupled with flagella propel the vesicle.

Theoretical model estimates propulsive force effectively.

Abstract

We study a synthetic system of motile Escherichia coli bacteria encapsulated inside giant lipid vesicles. Forces exerted by the bacteria on the inner side of the membrane are sufficient to extrude membrane tubes filled with one or several bacteria. We show that a physical coupling between the membrane tube and the flagella of the enclosed cells transforms the tube into an effective helical flagellum propelling the vesicle. We develop a simple theoretical model to estimate the propulsive force from the speed of the vesicles, and demonstrate the good efficiency of this coupling mechanism. Together, these results point to design principles for conferring motility to synthetic cells.