Figure 4. Directing the chemotactic self-organization of E. coli in the shape of a helix.

a–b) A conceptual schematic of the desired chemotactic self-organization. At the start of the experiment, a) the chemoattractant is confined to the container and the E. coli cells (represented by green ellipsoids) are distributed uniformly throughout the medium. b) E. coli cells self-organize in a helical pattern based on the underlying chemical pattern once the chemo-attractant (yellow) is allowed to diffuse out of the container. c1–c4) Experimental realization of the concept. Time-lapse images of green fluorescent E. coli as they self-organized in a helical pattern around a container with slits as shown in Figure 3. The number indicated in the left corner of each figure is the time lapse after the container was placed into the E. coli containing medium. The underlying chemical pattern was not visualized in this experiment.