Extracellular Electron Transfer Mechanisms Research Articles

Lack of physiological evidence for cytochrome filaments functioning as conduits for extracellular electron transfer.

Unraveling microbial extracellular electron transfer mechanisms has profound implications for environmental processes and advancing biological applications. This study on Geobacter sulfurreducens challenges prevailing beliefs on cytochrome filaments as crucial components thought to facilitate long-range electron transport. The discovery of an OmcS-deficient strain's unexpected effectiveness in Fe(III) oxide reduction prompted a reevaluation of the key conduits for extracellular electron transfer. By exploring the impact of genetic modifications on G. sulfurreducens' performance, this research sheds light on the importance of 3-nm diameter electrically conductive pili in Fe(III) oxide reduction. Reassessing these mechanisms is essential for uncovering the true drivers of extracellular electron transfer in microbial systems, offering insights that could revolutionize applications across diverse fields.

Mechanisms of extracellular electron transfer in anaerobic methanotrophic archaea

Anaerobic methanotrophic (ANME) archaea are environmentally important, uncultivated microorganisms that oxidize the potent greenhouse gas methane. During methane oxidation, ANME archaea engage in extracellular electron transfer (EET) with other microbes, metal oxides, and electrodes through unclear mechanisms. Here, we cultivate ANME-2d archaea (‘Ca. Methanoperedens’) in bioelectrochemical systems and observe strong methane-dependent current (91–93% of total current) associated with high enrichment of ‘Ca. Methanoperedens’ on the anode (up to 82% of the community), as determined by metagenomics and transmission electron microscopy. Electrochemical and metatranscriptomic analyses suggest that the EET mechanism is similar at various electrode potentials, with the possible involvement of an uncharacterized short-range electron transport protein complex and OmcZ nanowires.

Electrochemical Characterization of Two Gut Microbial Strains Cooperatively Promoting Multiple Sclerosis Pathogenesis.

In this study, we explored the extracellular electron transfer (EET) capabilities of two bacterial strains, OTU0001 and OTU0002, which are demonstrated in biofilm formation in mouse gut and the induction of autoimmune diseases like multiple sclerosis. OTU0002 displayed significant electrogenic behaviour, producing microbial current on an indium tin-doped oxide electrode surface, particularly in the presence of glucose, with a current density of 60 nA/cm2. The presence of cell-surface redox substrate potentially mediating EET was revealed by the redox-based staining method and electrochemical voltammetry assay. However, medium swapping analyses and the addition of flavins, a model redox mediator, suggest that the current production is dominated by soluble endogenous redox substrates in OTU0002. Given redox substrates were detected at the cell surface, the secreted redox molecule may interact with the cellular surface of OTU0002. In contrast to OTU0002, OTU0001 did not exhibit notable electrochemical activity, lacking cell-surface redox molecules. Further, the mixture of the two strains did not increase the current production from OTU0001, suggesting that OTU0001 does not support the EET mechanism of OTU0002. The present work revealed the coexistence of EET and non-EET capable pathogens in multi-species biofilm.

Nonelectroactive clostridium obtains extracellular electron transfer-capability after forming chimera with Geobacter.

Extracellular electron transfer (EET) of microorganisms is a major driver of the microbial growth and metabolism, including reactions involved in the cycling of C, N, and Fe in anaerobic environments such as soils and sediments. Understanding the mechanisms of EET, as well as knowing which organisms are EET-capable (or can become so) is fundamental to electromicrobiology and geomicrobiology. In general, Gram-positive bacteria very seldomly perform EET due to their thick non-conductive cell wall. Here, we report that a Gram-positive Clostridium intestinale (C.i) attained EET-capability for ethanol metabolism only after forming chimera with electroactive Geobacter sulfurreducens (G.s). Mechanism analyses demonstrated that the EET was possible after the cell fusion of the two species was achieved. Under these conditions, the ethanol metabolism pathway of C.i was integrated by the EET pathway of G.s, by which achieved the oxidation of ethanol for the subsequent reduction of extracellular electron acceptors in the coculture. Our study displays a new approach to perform EET for Gram-positive bacteria via recruiting the EET pathway of an electroactive bacterium, which suggests a previously unanticipated prevalence of EET in the microbial world. These findings also provide new perspectives to understand the energetic coupling between bacterial species and the ecology of interspecies mutualisms.

Magnetite-equipped algal-rich sediments for microbial fuel cells: Remediation of sediment organic matter pollution and mechanisms of remote electron transfer

Using the bio-electrochemical methods for the restoration of high algae sediments is full of potential and challenges. How to promote extracellular electron transfer (EET) process in microbial fuel cells (MFC) is the key bottleneck. The study had explored the potential application of magnetite on accelerating electron transfer for improving the output of MFC and sediment pollution remediation. The results indicated that the organic matter degradation rate showed a remarkable increase of 27.45 %, and the voltage output was approximately 1.68 times higher compared to the MFC configured with regular sediment. Abundant electroactive bacteria (EABs), such as Geobacter and Burkholderiaceae, and fermentative bacteria were responsible for these results, accompanied by the enhanced fluorescence of humic substances (HS), increased concentration and activity of cytochrome C (25.05 % and 21.12 %), as well as elevated extracellular polymeric substance content. Moreover, the intrinsic EET mechanisms among Fe-oxides, HS, and EABs were explored. According to the electrochemical analysis and substance transformation, the EET process involved four stages: magnetite-enhanced direct electron transfer via strong conductivity, iron respiration mediating electron transfer to the electrode, the model quinone substance acting as an electron shuttle facilitating EET and iron reduction, and iron cycling mediating electron transfer. This study provides an effective strategy for pollution remediation in algal-rich sediment, which was beneficial for the harmless treatment and resource utilization of both algae and sediment, simultaneously.

Bidirectional extracellular electron transfer pathways of Geobacter sulfurreducens biofilms: Molecular insights into extracellular polymeric substances

The basis for bioelectrochemical technology is the capability of electroactive bacteria (EAB) to perform bidirectional extracellular electron transfer (EET) with electrodes, i.e. outward- and inward-EET. Extracellular polymeric substances (EPS) surrounding EAB are the necessary media for EET, but the biochemical and molecular analysis of EPS of Geobacter biofilms on electrode surface is largely lacked. This study constructed Geobacter sulfurreducens-biofilms performing bidirectional EET to explore the bidirectional EET mechanisms through EPS characterization using electrochemical, spectroscopic fingerprinting and proteomic techniques. Results showed that the inward-EET required extracellular redox proteins with lower formal potentials relative to outward-EET. Comparing to the EPS extracted from anodic biofilm (A-EPS), the EPS extracted from cathodic biofilm (C-EPS) exhibited a lower redox activity, mainly due to a decrease of protein/polysaccharide ratio and α-helix content of proteins. Furthermore, less cytochromes and more tyrosine- and tryptophan-protein like substances were detected in C-EPS than in A-EPS, indicating a diminished role of cytochromes and a possible role of other redox proteins in inward-EET. Proteomic analysis identified a variety of redox proteins including cytochrome, iron-sulfur clusters-containing protein, flavoprotein and hydrogenase in EPS, which might serve as an extracellular redox network for bidirectional EET. Those redox proteins that were significantly stimulated in A-EPS and C-EPS might be essential for outward- and inward-EET and warranted further research. This work sheds light on the mechanism of bidirectional EET of G. sulfurreducens biofilms and has implications in improving the performance of bioelectrochemical technology.

Extracellular electron transfer for aerobic denitrification mediated by the bioelectric catalytic system with zero-carbon source

The slow rate of electron transfer and the large consumption of carbon sources are technical bottlenecks in the biological treatment of wastewater. Here, we first proposed to domesticate aerobic denitrifying bacteria (ADB) from heterotrophic to autotrophic by electricity (0.6 V) under zero organic carbon source conditions, to accelerate electron transfer and shorten hydraulic retention time (HRT) while increasing the biodegradation rate. Then we investigated the extracellular electron transfer (EET) mechanism mediated by this process, and additionally examined the integrated nitrogen removal efficiency of this system with composite pollution. It was demonstrated that compared with the traditional membrane bioreactor (MBR), the BEC displayed higher nitrogen removal efficiency. Especially at C/N = 0, the BEC exhibited a NO3--N removal rate of 95.42 ± 2.71 % for 4 h, which was about 6.5 times higher than that of the MBR. Under the compound pollution condition, the BEC still maintained high NO3--N and tetracycline removal (94.52 ± 2.01 % and 91.50 ± 0.001 %), greatly superior to the MBR (10.64 ± 2.01 % and 12.00 ± 0.019 %). In addition, in-situ electrochemical tests showed that the nitrate in the BEC could be directly converted to N2 by reduction using electrons from the cathode, which was successfully demonstrated as a terminal electron acceptor.

Influence of shear stress on electroactive biofilm characteristics and performance in microbial fuel cells

This study has provided comprehensive insights into the intricate relationship between shear stress and the development, structure, and functionality of electroactive biofilms in Microbial Fuel Cells (MFCs). A multichannel microfluidic MFC reactors that created specific shear stress on the anode, were designed for the simultaneous study of multiple flow conditions using the same medium. Then, the evolution of the biofilm growth under different shear stress conditions (1, 5 and 10 mPa) were compared. The taxonomic and functional structure was studied by 16S rRNA gene and metagenomic sequencing and the physical biofilm characteristics were measured via fluorescence microscopy. The results demonstrate the pivotal role of shear stress in influencing the growth kinetics, electrical performance, and physical structure of anodic biofilms. Notably, the selection of specific EAB was observed to be shear stress-dependent, with a marked increase in specific EAB abundance as shear stress increased. The power density, while not directly correlated with the relative abundance of specific or nonspecific EAB, exhibited a strong linear relationship with biofilm coverage. This suggests that factors beyond the microbial composition, potentially including mass transport or electrochemical conditions, might be instrumental in determining electricity production. The functional metagenomic analysis further highlighted the complexities of extracellular electron transfer (EET) mechanisms in electroactive biofilm. While certain genes associated with EET in known species such as Geobacter and Shewanella were identified, the study also examined the limitations of solely relying on genetic markers to infer EET capabilities, emphasizing the need for complementary metaproteomic analyses. This study demonstrates the multifaceted impact of shear stress on electroactive biofilm and paves the way for future investigations aimed at harnessing the potential of electroactive biofilms in microbial fuel cell applications.

Synergistic effect between sulfate-reducing bacteria and Shewanella algae on corrosion behavior of 321 stainless steel

Microbiologically influenced corrosion (MIC) caused by mixed microorganisms limits the application of 321 stainless steel (SS) in the field of ocean engineering. Therefore, in this paper, the synergistic effect of sulfate-reducing bacteria (SRB) and Shewanella algae (S. algae) on the corrosion behavior of 321 SS was studied by surface analysis and electrochemical measurements. The results revealed that riboflavin secreted by S. algae promoted the electron transfer between SRB and 321 SS by obtaining the electrons generated by the dissolution of metallic iron on the surface of SS and then transferring them to SRB, thus accelerating the MIC of 321 SS. Meanwhile, SRB gained electrons and reacted with SO42− to form HS−, which reacted with iron oxides in the Cr-rich passive film on the surface of SS to generate iron sulfides, providing thermodynamic and kinetic conditions for the formation of Cr6+. The formation of thermodynamically unstable Cr6+ destructed the passive film on the SS surface and promoted the development of pitting corrosion. The outcome provided a new perspective for studying the corrosion mechanism of extracellular electron transfer (EET)-MIC.

Bioelectrochemical system accelerates reductive dechlorination through extracellular electron transfer networks

Bioelectrochemical system is considered as a promising approach for enhanced bio-dechlorination. However, the mechanism of extracellular electron transfer in the dechlorinating consortium is still a controversial issue. In this study, bioelectrochemical systems were established with cathode potential settings at −0.30 V (vs. SHE) for trichloroethylene reduction. The average dechlorination rate (102.0 μM Cl·d−1) of biocathode was 1.36 times higher than that of open circuit (74.7 μM Cl·d−1). Electrochemical characterization via cyclic voltammetry illustrated that electrostimulation promoted electrochemical activity for redox reactions. Moreover, bacterial community structure analyses indicated electrical stimulation facilitated the enrichment of electroactive and dechlorinating populations on cathode. Metagenomic and quantitative polymerase chain reaction (qPCR) analyses revealed that direct electron transfer (via electrically conductive pili, multi-heme c-type cytochromes) between Axonexus and Desulfovibrio/cathode and indirect electron transfer (via riboflavin) for Dehalococcoides enhanced dechlorination process in BES. Overall, this study verifies the effectiveness of electrostimulated bio-dechlorination and provides novel insights into the mechanisms of dechlorination process enhancement in bioelectrochemical systems through electron transfer networks.

Advances in the Application of Quorum Sensing to Regulate Electrode Biofilms in Bioelectrochemical Systems

Bioelectrochemical systems (BESs) are an emerging technology for wastewater treatment and resource recovery. These systems facilitate electron transfer between microorganisms and electrodes, enabling their application in various fields, such as electricity production, bioremediation, biosensors, and biocatalysis. However, electrode biofilms, which play a critical role in BESs, face several challenges (e.g., a long acclimation period, low attached biomass, high electron transfer resistance, and poor tolerance and stability) that limit the development of this technology. Quorum sensing (QS) is a communication method among microorganisms that can enhance the performance of BESs by regulating electrode biofilms. QS regulation can positively impact electrode biofilms by enhancing extracellular electron transfer (EET), biofilm formation, cellular activity, the secretion of extracellular polymeric substances (EPS), and the construction of microbial community. In this paper, the characteristics of anode electrogenic biofilms and cathode electrotrophic biofilms in BESs, EET mechanisms, and the main factors affecting biofilm formation were summarized. Additionally, QS regulation mechanisms for biofilm formation, strategies for enhancing and inhibiting QS, and the application of QS regulation for electrode biofilms in BESs were systematically reviewed and discussed. This paper provides valuable background information and insights for future research and development of BES platforms based on QS regulation of electrode biofilms.

Comparing theoretical and practical biomass yields calls for revisiting thermodynamic growth models for electroactive microorganisms

Research on electroactive microorganisms (EAM) often focuses either on their physiology and the underlying mechanisms of extracellular electron transfer or on their application in microbial electrochemical technologies (MET). Thermodynamic understanding of energy conversions related to growth and activity of EAM has received only a little attention. In this study, we aimed to prove the hypothesized restricted energy harvest of EAM by determining biomass yields by monitoring growth of acetate-fed biofilms presumably enriched in Geobacter, using optical coherence tomography, at three anode potentials and four acetate concentrations. Experiments were concurrently simulated using a refined thermodynamic model for EAM. Neither clear correlations were observed between biomass yield and anode potential nor acetate concentration, albeit the statistical significances are limited, mainly due to the observed experimental variances. The experimental biomass yield based on acetate consumption (YX/ac = 37 ± 9 mgCODbiomass gCODac−1) was higher than estimated by modeling, indicating limitations of existing growth models to predict yields of EAM. In contrast, the modeled biomass yield based on catabolic energy harvest was higher than the biomass yield from experimental data (YX/cat = 25.9 ± 6.8 mgCODbiomass kJ−1), supporting restricted energy harvest of EAM and indicating a role of not considered energy sinks. This calls for an adjusted growth model for EAM, including, e.g., the microbial electrochemical Peltier heat to improve the understanding and modeling of their energy metabolism. Furthermore, the reported biomass yields are important parameters to design strategies for influencing the interactions between EAM and other microorganisms and allowing more realistic feasibility assessments of MET.

Interference of electron transfer chain inhibitors in bioelectrochemical systems

Substances inhibiting specific proteins involved in cellular electron transfer chains are used in biochemical research to investigate intracellular electron transfer routes and to redirect the electron fluxes. This also provides an in vivo approach to investigating the extracellular electron transfer (EET) mechanisms within and across biological membranes in bioelectrochemical research. However, the applicability of these specific inhibitors in electrochemical systems remains to be validated, particularly when aiming for (semi-)quantitative evaluation of the contribution of specific redox proteins to the EET. Here we conducted a systematic analysis of commonly used inhibitors and discovered several of them to be electrochemically active and thus capable of interfering with measurements in a bioelectrochemical reactor system in abiotic experiments. We also observed effects in vivo using a biophotovoltaics reactor with Synechocystis sp. PCC 6803 as a model system.

Electroactive Bacteria in Natural Ecosystems and Their Applications in Microbial Fuel Cells for Bioremediation: A Review

Electroactive bacteria (EAB) are natural microorganisms (mainly Bacteria and Archaea) living in various habitats (e.g., water, soil, sediment), including extreme ones, which can interact electrically each other and/or with their extracellular environments. There has been an increased interest in recent years in EAB because they can generate an electrical current in microbial fuel cells (MFCs). MFCs rely on microorganisms able to oxidize organic matter and transfer electrons to an anode. The latter electrons flow, through an external circuit, to a cathode where they react with protons and oxygen. Any source of biodegradable organic matter can be used by EAB for power generation. The plasticity of electroactive bacteria in exploiting different carbon sources makes MFCs a green technology for renewable bioelectricity generation from wastewater rich in organic carbon. This paper reports the most recent applications of this promising technology for water, wastewater, soil, and sediment recovery. The performance of MFCs in terms of electrical measurements (e.g., electric power), the extracellular electron transfer mechanisms by EAB, and MFC studies aimed at heavy metal and organic contaminant bioremediationF are all described and discussed.

Carbon dots internalization enhances electroactive biofilm formation and microbial acetate synthesis

This study investigated how carbon dots (CDs) and N-doped CDs modification of acetogenic bacteria enhanced the extracellular electron transfer (EET) and the formation of electroactive biofilm, which subsequently improved acetate production from CO2 in microbial electrosynthesis (MES). Characteristic fluorescence emission peaks of CDs and N-doped CDs were detected inside and outside of bacterial cells, respectively, suggesting that the CDs were successfully internalized by the cells. The (N-doped) CDs modified acetogens increased current output by 89–95%, and acetate production rate by 57–71%. The highest acetate production rate and electron recovery efficiency reached 2.1 mM d−1 and 91.3%, respectively. Acetoanaerobium and Sporomusa, which are considered to have different EET strategies, dominated the biocathodes modified with CDs and N-doped CDs, respectively. The CDs modification increased biofilm thickness by 86% and reached 41.0 ± 1.3 μm, which could be related to the increased secretion of flavins that enhanced the signal transduction interspecies. With the N-doped CDs modified, the biofilm was occupied with active pyrrolic N/graphitic N (52%), and the expression of functional genes encoding cytochrome (cydB, cybH, CcdA) were enhanced significantly. This study offers insights into the EET mechanisms by acetogens and a viable approach to increase acetate production from CO2.

Electro-stimulated anaerobic oxidation of methane with synergistic denitrification by adding AQS: Electron transfer mode and mechanism

Denitrifying anaerobic methane-oxidizing (DAMO) processes, which link anaerobic methane oxidation (AMO) and denitrification, have a promising prospect in anaerobic wastewater treatment. In bioelectrochemical systems (BES), DAMO consortium presented potent metabolic activity. However, the extracellular electron transfer (EET) in BES was poorly understood. This study investigated the EET mechanisms and modes of electron transport in BES dominated by anaerobic methanotrophic bacteria. In the bioreactors with the auxiliary voltage of 0.5 and 1.1 V, named EMN-0.5 and EMN-1.1, respectively, biological voltages of 0.198 and 0.329 V were generated with power densities of 0.6 and 1.20 mW/m2, after removing the voltage. High throughput and metagenome analyses demonstrated that main methanotrophs were DAMO bacteria and Methylocystis sp. The electroactive bacteria detected were Pseudomonas sp., Hypomicrobium sp., Thiobacillus sp, and Rhodococcus sp. The pil, cytochrome c, hdr, and he/fp genes related to EET were present on the electrode surfaces. Carbon 13 isotope tracing and chemicals analysis by GC-MS exhibited that methanol was an intermediate product released to extracellular environment and acted as the electronic carrier to drive the EET in methane oxidation. Extracellular electron transfer was achieved through the collaboration of DAMO bacteria, Methylocystis sp., and Pseudomonas sp. Anthraquinone 2-sulfonic acid ester (AQS) could improve the rate of electron transfer to the extracellular space, especially in the EMN-0.5 reaction system. This study provides a new understanding of AMO consortium metabolism in BES and may provide a scientific basis for developing methane control technology.

Direct extracellular electron transfer to an indium tin doped oxide electrode via heme redox reactions in Desulfovibrio ferrophilus IS5

Soluble redox mediators have been hypothesized to play a major role in cellular electron transportation to extracellular insoluble electron acceptors in sulfate-reducing bacteria (SRB) through a diffusion-based electron shuttle mechanism. Herein, in vivo electrochemistry shows that outer-membrane cytochromes (OMCs) directly mediated extracellular electron transfer (EET) in Desulfovibrio ferrophilus IS5. Anodic current production by IS5, coupled with lactate oxidation, was detected on indium-tin-doped oxide electrodes poised at +400 mV (vs. standard hydrogen electrode), which was the sole electron acceptor. Subsequent electrolyte replacement experiments with a fresh one showed that cells attached to the electrode contributed to 73% of current production by direct EET, while the electron shuttle mechanism may have contributed to the rest. Differential pulse voltammetry detected two redox species at E = −180 and 20 mV, with the former being most likely assignable to cell-surface cytochromes because nitric oxide decreased the peak current at −180 mV, as previously demonstrated with OMCs in iron-reducing bacteria. The EET onset potential at −200 mV further supports the notion that OMCs mediated EET in IS5, and that EET is thermodynamically favorable for reducing Fe(III) oxide. These results suggest that the direct EET mechanism regulates the reduction rate of insoluble substrates in SRB.

Moving towards the enhancement of extracellular electron transfer in electrogens

Electrogens are very common in nature and becoming a contemporary theme for research as they can be exploited for extracellular electron transfer. Extracellular electron transfer is the key mechanism behind bioelectricity generation and bioremediation of pollutants via microbes. Extracellular electron transfer mechanisms for electrogens other than Shewanella and Geobacter are less explored. An efficient extracellular electron transfer system is crucial for the sustainable future of bioelectrochemical systems. At present, the poor extracellular electron transfer efficiency remains a decisive factor in limiting the development of efficient bioelectrochemical systems. In this review article, the EET mechanisms in different electrogens (bacteria and yeast) have been focused. Apart from the well-known electron transfer mechanisms of Shewanella oneidensis and Geobacter metallireducens, a brief introduction of the EET pathway in Rhodopseudomonas palustris TIE-1, Sideroxydans lithotrophicus ES-1, Thermincola potens JR, Lysinibacillus varians GY32, Carboxydothermus ferrireducens, Enterococcus faecalis and Saccharomyces cerevisiae have been included. In addition to this, the article discusses the several approaches to anode modification and genetic engineering that may be used in order to increase the rate of extracellular electron transfer. In the side lines, this review includes the engagement of the electrogens for different applications followed by the future perspective of efficient extracellular electron transfer.

Extracellular electron transfer corrosion mechanism of two marine structural steels caused by nitrate reducing Halomonas titanicae

The extracellular electron transfer (EET) mechanism for corrosion of EH36 steel (with copper) and Q235 steel (without copper) caused by Halomonas titanicae was investigated. Due to copper cytotoxicity, the sessile H. titanicae cells on the EH36 surface was only 18% of that on Q235. This led to its lower EET rate, resulting in EH36 corrosion being 0.67 times of Q235 corrosion. The EET corrosion mechanism was further proven by the increased corrosion of the two steels after injection to the H. titanicae broth of 20 ppm (w/w) (in the broth) riboflavin, an electron mediator known to accelerate EET.

Enhanced purification of kitchen-oil wastewater driven synergistically by surface microelectric fields and microorganisms

The stable structure and toxic effect of refractory organic pollutants in wastewater lead to the problem of high energy consumption in water treatment technology. Herein, we propose a synergistic purification of refractory wastewater driven by microorganisms and surface microelectric fields (SMEF) over a dual-reaction-center (DRC) catalyst HCLL-S8-M prepared by an in situ growth method of carbon nitride on the Cu-Al2O3 surface. Characterization techniques demonstrate the successful construction of SMEF with strong electrostatic force over HCLL-S8-M based on cation-π interactions between metal copper ions and carbon nitride rings. With the catalyst as the core filler, an innovative fixed bed bioreactor is constructed to purify the actual kitchen-oil wastewater. The removal efficiency of the wastewater even with a very low biodegradability (BOD5/COD = 0.33) can reach 60% after passing through this bioreactor. An innovative reaction mechanism is revealed for the first time that under the condition of a small amount of biodegradable organic matter, the SMEF induces the enrichment of electric active microorganisms (Desulfobulbus and Geobacter) in the wastewater, accelerates the interspecies electron transfer of intertrophic metabolism with the biodegradable bacteria through the extracellular electron transfer mechanism such as cytochrome C and self-secreted electron shuttle. The electrons of the refractory organic pollutants adsorbed on the surface of the catalyst are delocalized by the SMEF, which can be directly utilized by microorganisms through EPS conduction. The SMEF generated by electron polarization can maximize the utilization of pollutants and microorganisms in wastewater and further enhance degradation without adding any external energy, which is of great significance to the development of water self-purification technology.