(572ax) Chemotaxis of Artificial Protocells

The ability of both single-cellular and higher organisms to actively move in the concentration gradient of a signalling molecule ? whether to seek a source of nutrient or a partner to mate ? is one of the most prominent external signs of life: ?it moves, hence it must be alive!?. Mimicking chemotaxis in artificial or bio-artificial systems is a challenging task; usually the objective is to devise a bio-mechanic apparatus such as a flagellum in order to ensure active propulsion. However, chemotaxis based on such bio-mechanic principles still remains an elusive task. In this work we will present a different approach to achieving chemotaxis in artificial protocell (i.e. simple, synthetic particles possessing one or more functions of real cells). This approach, which we term ?probabilistic chemotaxis' is based on the combination of random Brownian motion and specific particle-substrate interaction, the strength of which is designed to be a function of the concentration of the desired signalling molecule. Provided that the interaction is reversible, the repetition of adhesion-release events leads to a bias random walk, whereby a swarm of proto-cells gradually migrates in the direction of the concentration gradient. We will present experimental data demonstrating this chemotaxis mechanism, and discuss the potential for its further development, in particular the signal amplification and cooperative behaviour due to cell-cell signalling.