A Micro "Flea Circus": Self Assembly of Bacteria Through Spatio-Temporal Control of Aerotaxis

We present a new microfluidic method for dynamically assaying bacterial aerotaxis and controlling taxis-based bacterial self-assembly. The method utilizes an electrochemical oxygen-generating technology previously developed by our group [ 1]. This device uses electrolysis at many microelectrodes to generate controlled doses of dissolved oxygen; these doses can be superimposed to pattern microscale gradients with precise spatial and temporal resolution. We demonstrate our method by performing aerotaxis experiments with B. subtilis, an obligatory aerobe. We show how this method of generating oxygen gradients with microscale resolution can be used to perform: 1) dynamic response assays of traditional bacterial suspensions not possible with existing methods, and 2) studies on oxygen responses of single bacterium. We also show that the basic premise only functions in a microscale environment. Lastly, we demonstrate how this method can be used to self-assemble large-density and small numbers of bacteria into pre-determined patterns using aerotaxis.