Molecular Insights into the Response of Nonelectroactive Bacteria to Electro-stimulation: Growth and Metabolism Regulation Mechanism

Understanding how nonelectroactive bacteria (non-EAB) perceive and respond to electro-stimulation is pivotal for optimizing electro-biostimulation systems. Here, Escherichia coli, a representative non-EAB, was employed to investigate its electrical response behavior and molecular regulatory mechanism across a spectrum of current densities. Accelerated bacterial growth was observed at current densities ranging from 2 to 10 A m^-2 with a maximum growth rate of 1.89 h^-1 at 10 A m^-2. Moderate electrostimulation (10 A m^-2) promoted NADH regeneration and adenosine triphosphate synthesis by modulating intracellular glycolytic flux, tricarboxylic acid (TCA) cycle and electron transport chain (ETC), while cells became inactivated at 20 A m^-2 mainly due to the overall inhibition of the TCA cycle and domino collapse of ETC. The presence of reductive stress caused by electro-stimulation not only promoted NADPH and glutamine consumption but also impacted the material exchange fluxes by altering outer membrane proteins (OMPs) from β-fold to β-corner. Additionally, extracellular polymeric substances served as the electron transient medium to sense electro-stimulation. The study revealed that non-EAB possessed approaches different from EET to sense and respond to electro-stimulation. The improved comprehension of regulatory mechanisms governing catabolic pathways under electro-stimulation holds promise for developing more efficient electro-biostimulation systems, with implications for environmental biotechnology applications.