Bioelectricity enhancement via overexpression of quorum sensing system in Pseudomonas aeruginosa-inoculated microbial fuel cells.

Low electron transfer efficiency from bacteria to electrodes remains one of the major bottlenecks that limit industrial applications of microbial fuel cells (MFCs). Elucidating biological mechanism of the electron transfer processes is of great help in improving the efficiency of MFCs. Here, we reported that Pseudomonas aeruginosa could use different electron shuttles in a MFC under different quorum sensing (QS) expression patterns. An electron shuttle (rather than phenazines) with a high mid-point potential of 0.20 V (vs. Ag/AgCl-KCl saturated electrode) was found to be the dominating shuttle in a wild-type P. aeruginosa strain. Strikingly, upon genetic overexpression of rhl QS system in this wild-type strain, the electron shuttle was substituted by phenazines (pyocyanin and phenazine-1-carboxylate, with a low mid-point potential of -0.17 V and -0.28 V, respectively), which directly resulted in an increase of about 1.6 times of the maximum current of the rhl overexpressed strain over the wild-type strain. Our result implied that manipulating electron transfer pathways to improve MFCs' efficiency could be achieved by rewiring gene regulatory circuits, thus synthetic biology strategies would be adopted.