Modulation of gene expression via directed electrical signaling; voltage sensitive promoters

The ability to interface biology with electronic components is extremely limited, in large measure because cells do not readily recognize electronic inputs in a way that we understand.  Electrical connectivity in biological systems is mediated by kinetically isolated sets of chemical mediators, including pools of flavins, nicotinamides, glutathione carbon sources and oxygen (for example).  The key challenge towards achieving facile “communication” between biologics and electronics is finding ways in which electrical inputs from electronics can be converted into chemical signals that can be “understood” by cells.  In this work, we aim to increase the toolbox of bioengineers by achieving direct electrical control of transcription in E. coli through organic dye (redox mediator) assisted electron transfer into cells. As the dyes exchange electrons directly with an electrode surface, they serve as a “switching point” to convert electrical input into a chemical signal, which can be sensed by the cell through binding to proteins or alterations of intracellular chemistries. Transcriptome analyses of E. coli, in the context of a microbial fuel cell, have been conducted and we have found several highly regulated genes of interest. The expression regulators upstream of these genes will be used in fluorescent protein expression plasmids for quantitative expression assays to validate electrical control of expression and test the efficacy of such a system in synthetic applications. By utilizing multiple redox mediators, we will also investigate “multiplexing” of our system, wherein multiple gene expression profiles could be altered simply be tuning the applied electrical potential. Achieving this would give us a digitally controlled expression system that can be used in bulk fermentation applications, among numerous other applications.