Programming Bioelectronic Bacteria as Real-Time and Multi-Channel Sensors

Challenged by a changing climate, dwindling natural resources, and a growing global population, we need advanced renewable materials that meld the sustainability of biological materials with the functionality of conventional materials. To help address this need, my research group creates sustainable and environmentally-responsive living materials by seamlessly integrating conventional materials with living systems. One major effort in our group is to co-engineer microorganisms and microelectronics to serve as living bioelectronic sensors that can selectively sense a variety of complex molecules in real-time.<br/><br/>In my talk, I will first describe a collaborative project with the Silberg group at Rice to develop bioelectronic sensors that have minute detection times. We programmed <i>Escherichia coli</i> to produce current in response to specific chemicals using a modular, eight-component, synthetic electron transport chain. As designed, this strain produced electrical current upon exposure to thiosulfate, an anion that causes microbial blooms, in two minutes. By incorporating a protein switch into the synthetic pathway and encapsulating the bacteria with conductive nanomaterials, this amperometric sensor could be modified to detect an endocrine disruptor within two minutes in riverine water. Our results provide design rules to sense a variety of chemicals with mass transport-limited detection times and a new platform for miniature, low-power bioelectronic sensors that safeguard ecological and human health.<br/><br/>In the second part of my talk, I will describe how we have created bioelectronic sensors that convey multiple channels of information. Existing bioelectronic sensors can sense a variety of hazards to human and environmental health, however, these sensors transmit information through only a single electrochemical channel. This severely limits the amount of sensing information that can be transmitted. To increase this information content, we developed a multichannel bioelectronic sensor in which different chemicals modulate distinct extracellular electron transfer pathways in <i>E. coli</i>. To create an <i>E. coli</i> strain with two reporting channels, we introduced a riboflavin synthesis pathway from <i>Bacillus subtilis</i> alongside the metal reducing (Mtr) pathway from <i>Shewanella</i> <i>oneidensis</i>. We can distinguish whether one or both pathways are active in this strain using either chronoamperometry or a series of amperometric measurements at distinct redox potentials. To demonstrate multi-channel bioelectronic sensing, we regulated the Mtr and riboflavin pathways using arsenic and cadmium responsive promoters. With this strain, we used a series of amperometric measurements at distinct redox potentials to distinguish the presence of the different heavy metals <i>in situ</i>. These accomplishments provide a new platform for multichannel bioelectronic sensors that simultaneously detect and report multiple toxins.