Actuation of synthetic cells with proton gradients generated by light-harvesting E. coli

Bottom-up and top-down approaches to synthetic biology each employ distinct methodologies with the common aim to harness new types of living systems. Both approaches, however, face their own challenges towards biotechnological and biomedical applications. Here, we realize a strategic merger to convert light into proton gradients for the actuation of synthetic cellular systems. We genetically engineer E. coli to overexpress the light-driven inward-directed proton pump xenorhodopsin and encapsulate them as organelle mimics in artificial cell-sized compartments. Exposing the compartments to light-dark cycles, we can reversibly switch the pH by almost one pH unit and employ these pH gradients to trigger the attachment of DNA structures to the compartment periphery. For this purpose, a DNA triplex motif serves as a nanomechanical switch responding to the pH-trigger of the E. coli. By attaching a polymerized DNA origami plate to the DNA triplex motif, we obtain a cytoskeleton mimic that considerably deforms lipid vesicles in a pH-responsive manner. We foresee that the combination of bottom-up and top down approaches is an efficient way to engineer synthetic cells as potent microreactors.