Mesoporous PU/PEDOT:PSS Electrodes Reveal Population-Level Stochastic Bioelectrical Dynamics in Marine Diatoms

Understanding how microbial populations generate and modulate electrical signals remains a major technical challenge because extracellular ionic processes are inherently weak, spatially distributed and stochastic. Here, we introduce a mesoporous ultra-low-impedance PEDOT:PSS electrode that exploits volumetric ionic-electronic coupling to probe stochastic electrochemical dynamics in axenic populations of the marine model diatom Phaeodactylum tricornutum. The three-dimensional porous architecture provides a large electrochemically accessible surface area with high capacitance and low impedance, enabling sensitive detection of non-equilibrium current fluctuations under applied bias. Applied bias systematically amplifies stochastic electrical fluctuations, while living diatoms significantly modify their amplitude and temporal statistics. Noise analysis reveals enhanced low-frequency fluctuations, increased power-law exponents and higher transient-event rates, indicating biologically driven perturbations of the local electrochemical environment. Pharmacological inhibition with tetraethylammonium suppresses spontaneous electrical activity, providing independent functional evidence that membrane-associated potassium-dependent processes contribute to the measured signals. Increasing diatom cell density further produces progressively larger spectral exponents and distinct changes in stochastic-event dynamics, demonstrating that these electrical signatures encode microbial population density. These findings establish stochastic electrochemical noise as a sensitive, label-free probe of microbial bioelectrochemical activity and a bioelectronic strategy for monitoring living microbial systems through their intrinsic non-equilibrium electrical fluctuations.