Increasing Cell Width and Volume to Boost Extracellular Electron Transfer Rate for Enhanced Bioelectricity Harvest and Pollution Treatment

Cell dimension, including length and width, is an essential physiological feature that significantly influences extracellular electron transfer (EET). However, previous research has focused on the effects of cell length on electrophysiology and metabolic physiology, while the relationship between the cell width and EET remains unexplored. In this study, we increased cellular width of the model exoelectrogen, Shewanella oneidensis, by inhibiting the formation of the elongasome using antisense RNAs, thus enhancing the power density to 2.3-fold that of the wild-type (WT) S. oneidensis. Electrophysiological and metabolic physiology analyses revealed that programmed cell widening enhanced direct EET by increasing the abundance of c-type cytochrome and facilitating the initial adhesion and vertical expansion of the electroactive biofilm. Additionally, assembly with a cell elongation module expanded the cell volume to 269.2-fold compared to the WT. However, the decreased specific surface area slowed lactate uptake, which was resolved through global regulation mediated by the cAMP receptor protein. To further increase the indirect EET, we integrated the riboflavin biosynthetic pathway into the above engineered strain, obtaining a power density of 2225.7 ± 148.5 mW m–2, a 30.6-fold increase over the WT, with enhanced bioelectricity recovery and pollutant treatment abilities. This study indicated the detailed mechanism how cell width and volume impacts electrophysiology, proposing that cell widening and volume expanding is a promising avenue to augment power production of electroactive microorganisms.