A synthetic gene circuit to convert biochemical signals to electrical signal in engineered sensory bacteria for electrochemical biosensing

Abstract

The intracellular gene circuit to transform biochemical signals to an electrical signal is the key for biosensor development to gap the information mismatch at the bio-electric interface, but a qualified gene circuit is difficult to design. In this study, we have shown the construction of an integrated synthetic gene circuit including the nitric oxide (NO)-responsive module and the phenylenediamine-1-carboxylic acid (PCA) synthesis module, to (1) equip a less renounced electroactive bacterium (e.g. Escherichia coli) with indirect electron transfer (IET) pathway to enhance electrical signal output, as well as (2) couple the IET gene circuit with the responsive gene circuit to sense small signal molecule, NO. The subsequent oxidation of PCA can be electrochemically quantified by the microelectrode, thereby establishing a signaling pathway from intracellular message to redox mediator, and finally to electrical signal output. In this way, the constructed microbial electrochemical biosensor for intracellular in situ NO analysis at the single-cell level owns high sensitivity, a wide linear detection range (100–2500 nM), and excellent selectivity. Therefore, this work shows an example for developing next-generation electroactive microorganisms (EAMs)-based electrochemical biosensors through synthetic biology tools with tailored and intelligent functionalities.