Discover insights from thousands of peer-reviewed papers on microbial electrochemical systems
Yinxiu Liang, Min Ji, Hongyan Zhai et al.
The Science of The Total Environment · 2021
Yuan Li, Kai Liu, Rongrong Mao et al.
Journal of Hazardous Materials · 2022
Carolina Cruz Viggi, Matteo Tucci, Marco Resitano et al.
Bioengineering · 2023
Anaerobic bioremediation is a relevant process in the management of sites contaminated by petroleum hydrocarbons. Recently, interspecies electron transfer processes mediated by conductive minerals or particles have been proposed as mechanisms through which microbial species within a community share reducing equivalents to drive the syntrophic degradation of organic substrates, including hydrocarbons. Here, a microcosm study was set up to investigate the effect of different electrically conductive materials (ECMs) in enhancing the anaerobic biodegradation of hydrocarbons in historically contaminated soil. The results of a comprehensive suite of chemical and microbiological analyses evidenced that supplementing the soil with (5% w / w ) magnetite nanoparticles or biochar particles is an effective strategy to accelerate the removal of selected hydrocarbons. In particular, in microcosms supplemented with ECMs, the removal of total petroleum hydrocarbons was enhanced by up to 50% relative to unamended controls. However, chemical analyses suggested that only a partial bioconversion of contaminants occurred and that longer treatment times would have probably been required to drive the biodegradation process to completion. On the other hand, biomolecular analyses confirmed the presence of several microorganisms and functional genes likely involved in hydrocarbon degradation. Furthermore, the selective enrichment of known electroactive bacteria (i.e., Geobacter and Geothrix ) in microcosms amended with ECMs, clearly pointed to a possible role of DIET (Diet Interspecies Electron Transfer) processes in the observed removal of contaminants.
Lecheng Liu, Guangfei Liu, Jiti Zhou et al.
Environmental Science & Technology · 2021
The fate and transport of bacteria in porous media are essential for bioremediation and water quality control. However, the influence of biological activities like extracellular electron transfer (EET) and swimming motility toward granular media on cell transport remains unknown. Here, electroactive bacteria with higher Fe(III) reduction abilities were found to demonstrate greater retention in ferrihydrite-coated sand. Increasing the concentrations of the electron donor (1-10 mM lactate), shuttle (0-50 μM anthraquinone-2,6-disulfonate), and acceptor (ferrihydrite, MnO 2 , or biochar) under flow conditions significantly reduced Shewanella oneidensis MR-1's mobility through redox-active porous media. The deficiency of EET ability or flagellar motion and inhibition of intracellular proton motive force, all of which are essential for energy taxis, enhanced MR-1's transport. It was proposed that EET could facilitate MR-1 to sense, tactically move toward, and attach on redox-active media surface, eventually improving its retention. Positive linear correlations were established among parameters describing MR-1's energy taxis ability (relative taxis index), cell transport behavior (dispersion coefficient and relative change of effluent percentage), and redox activity of media surface (reduction potential or electron-accepting rate), providing novel insights into the critical impacts of bacterial microscale motility on macroscale cell transport through porous media.
Tejedor-Sanz Sara, P. Fernández-Labrador, Carlos Manchón et al.
Electrochemistry Communications · 2020
Microbial Electrochemical Fluidized Bed Reactors (ME-FBR) represent a new concept for promoting proper bacteria-electrode interaction and eventually efficient biocatalysis in Microbial Electrochemical Technologies (METs). In the current work we demonstrate how a fluidized cathode, a dynamic and discontinuous design of electrode, can be an effective electron donor for electroactive hydrogen-generating and nitrate reducing bacteria. Furthermore, the oxygen produced in the anodic reaction promoted ammonium oxidation to nitrate by nitrifying bacteria thus expanding the environmental applications of the system. By coupling both anodic and cathodic reactions, it was possible to simultaneously achieve nitrification–denitrification within one chamber and without external oxygen addition. Our proof-of-concept revealed the removal of 98% ammonium and ca. 29% of total nitrogen (31 g-N m−3reactor d−1) from an effluent with low organic matter under continuous mode. This study reveals for first time how fluidized beds can be integrated in METs not only as anodes but also as cathodes, broadening the opportunities and applications to bioremediation and bioelectrosynthesis processes.
Xin Li, Shiling Zheng, Yinhao Li et al.
Journal of Hazardous Materials · 2023
Xuliang Zhuang, Shijie Wang, Shanghua Wu
Life · 2024
Microorganisms are key players in the global biogeochemical sulfur cycle. Among them, some have garnered particular attention due to their electrical activity and ability to perform extracellular electron transfer. A growing body of research has highlighted their extensive phylogenetic and metabolic diversity, revealing their crucial roles in ecological processes. In this review, we delve into the electron transfer process between sulfate-reducing bacteria and anaerobic alkane-oxidizing archaea, which facilitates growth within syntrophic communities. Furthermore, we review the phenomenon of long-distance electron transfer and potential extracellular electron transfer in multicellular filamentous sulfur-oxidizing bacteria. These bacteria, with their vast application prospects and ecological significance, play a pivotal role in various ecological processes. Subsequently, we discuss the important role of the pili/cytochrome for electron transfer and presented cutting-edge approaches for exploring and studying electroactive microorganisms. This review provides a comprehensive overview of electroactive microorganisms participating in the biogeochemical sulfur cycle. By examining their electron transfer mechanisms, and the potential ecological and applied implications, we offer novel insights into microbial sulfur metabolism, thereby advancing applications in the development of sustainable bioelectronics materials and bioremediation technologies.
Yang Bai, Bin Liang, Hui Yun et al.
Journal of Hazardous Materials · 2020
Haloaromatic antimicrobial triclocarban (TCC) is an emerging refractory contaminant that commonly coexisted with conventional contaminants such as polycyclic aromatic hydrocarbons (PAHs). TCC may negatively affect the metabolic activity of sediment microorganisms and persist in environment; however, remediation methods that relieve the TCC inhibitory effect in sediments remain unknown. Here, a novel electro-biostimulation and bioaugmentation combined remediation system was proposed by the simultaneous introduction of a TCC-degrading Ochrobactrum sp. TCC-2 and electrode into the TCC and PAHs co-contaminated sediments. Results indicated the PAHs and TCC degradation efficiencies of the combined system were 2.9-3.0 and 4.6 times respectively higher than those of the control group (no electro-biostimulation and no bioaugmentation treatments). The introduced strain TCC-2 and the enriched electroactive bacteria and PAHs degraders (e.g. Desulfobulbus, Clostridium, and Paenarthrobacter) synergistically contributed to the accelerated degradation of PAHs and TCC. The preferential elimination of the TCC inhibitory effect through bioaugmentation treatment could restore microbial functions by increasing the functional gene abundances related to various metabolic processes. This study offers new insights into the response of sediment functional communities to TCC stress, electro-biostimulation and bioaugmentation operations and provides a promising system for the enhanced bioremediation of the PAHs and TCC co-contaminated sediments.
Ke Shi, Bin Liang, Qiu Guo et al.
Journal of Hazardous Materials · 2021
Juan Anaya-Garzon, Suanny Mosquera-Romero, Luis Fernando León‐Fernandez et al.
SSRN Electronic Journal · 2022
Debasa Mukherjee, Lucinda Elizabeth Doyle
Electrochimica Acta · 2024
Guowei Chen, Renhao Shen, Yifei Sun et al.
Journal of Water Process Engineering · 2024
Élise Cachat, Weijia Liu, K. Martin et al.
Scientific Reports · 2016
Synthetic biology provides an opportunity for the construction and exploration of alternative solutions to biological problems - solutions different from those chosen by natural life. To this end, synthetic biologists have built new sensory systems, cellular memories, and alternative genetic codes. There is a growing interest in applying synthetic approaches to multicellular systems, especially in relation to multicellular self-organization. Here we describe a synthetic biological system that confers large-scale de novo patterning activity on 2-D and 3-D populations of mammalian cells. Instead of using the reaction-diffusion mechanisms common in real embryos, our system uses cadherin-mediated phase separation, inspired by the known phenomenon of cadherin-based sorting. An engineered self-organizing, large-scale patterning system requiring no prior spatial cue may be a significant step towards the construction of self-assembling synthetic tissues.
Glenn Quek, Ricardo Javier Vázquez, Samantha R. McCuskey et al.
Angewandte Chemie · 2023
Abstract Interfacing bacteria as biocatalysts with an electrode provides the basis for emerging bioelectrochemical systems that enable sustainable energy interconversion between electrical and chemical energy. Electron transfer rates at the abiotic‐biotic interface are, however, often limited by poor electrical contacts and the intrinsically insulating cell membranes. Herein, we report the first example of an n‐type redox‐active conjugated oligoelectrolyte, namely COE‐NDI , which spontaneously intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. The incorporation of COE‐NDI into Shewanella oneidensis MR‐1 cells amplifies current uptake from the electrode by 4‐fold, resulting in the enhanced bio‐electroreduction of fumarate to succinate. Moreover, COE‐NDI can serve as a “protein prosthetic” to rescue current uptake in non‐electrogenic knockout mutants.
Priyadharshini Mani, T. Keshavarz, T.S. Chandra et al.
Enzyme and Microbial Technology · 2016
Kamran Ayaz, Ewa Zabłocka-Godlewska, Abdullah et al.
Journal of environmental chemical engineering · 2026
Enhancing bioelectrochemical performance through electrode modifications is critical for advancing microbial fuel cell (MFC) technology. This study investigates the effect of carbon cloth modifications using polyaniline (PANI), glucose, and gelatin on biofilm formation, charge transfer, and microbial viability. Cyclic voltammetry results of initial and 7-day performance demonstrate that PANI-glucose-gelatin-biofilm modified carbon cloth (MCC.B) exhibits highest maximum current and lowest charge transfer resistance when compared with a bare carbon cloth-biofilm system with (CC.G.B) and without (CC.B) the presence of dissolved glucose. Biofilm viability studies reveal that CC.G.B supports predominantly planktonic growth, limiting bacterial adhesion, while MCC.B achieves the highest biofilm formation (90.2 ± 0.2%) and charge storage capacity (174.9 ± 10.2 mC/cm 2 ), corresponding to an approximately 50-fold increase in CSC compared with a bare carbon cloth system (3.3 ± 0.3 mC/cm 2 ), highlighting the synergistic impact of surface modifications and microbial activity. These findings demonstrate that MCC.B facilitates extracellular electron transfer by optimizing bacterial adhesion and nutrient availability, making it a promising candidate for shortening start-up and improving early-stage bioelectrode performance, while longer-term stability remains to be established. This work provides new insights into electrode engineering strategies for maximizing microbial interaction and electrochemical performance in next-generation microbial electrochemical technologies. • Novel electrode modification strategy for microbial fuel cells was developed. • Carbon cloth was modified with polyaniline, glucose, and a protective gelatin layer. • Higher biofilm adhesion and improved cell viability were observed on modified electrodes. • Higher capacitance and lower charge transfer resistance were noted with modified carbon cloth.
Dinesh Gupta, Molly C. Sutherland, Karthikeyan Rengasamy et al.
mBio · 2019
Photoferrotrophy is a form of anoxygenic photosynthesis whereby bacteria utilize soluble or insoluble forms of ferrous iron as an electron donor to fix carbon dioxide using light energy. They can also use poised electrodes as their electron donor via phototrophic extracellular electron uptake (phototrophic EEU). The electron uptake mechanisms underlying these processes are not well understood. Using Rhodopseudomonas palustris TIE-1 as a model, we show that a single periplasmic decaheme cytochrome c , PioA, and an outer membrane porin, PioB, form a complex allowing extracellular electron uptake across the outer membrane from both soluble iron and poised electrodes. We observe that PioA undergoes postsecretory proteolysis of its N terminus to produce a shorter heme-attached PioA (holo-PioA C , where PioA C represents the C terminus of PioA), which can exist both freely in the periplasm and in a complex with PioB. The extended N-terminal peptide controls heme attachment, and its processing is required to produce wild-type levels of holo-PioA C and holo-PioA C B complex. It is also conserved in PioA homologs from other phototrophs. The presence of PioAB in these organisms correlate with their ability to perform photoferrotrophy and phototrophic EEU. IMPORTANCE Some anoxygenic phototrophs use soluble iron, insoluble iron minerals (such as rust), or their proxies (poised electrodes) as electron donors for photosynthesis. However, the underlying electron uptake mechanisms are not well established. Here, we show that these phototrophs use a protein complex made of an outer membrane porin and a periplasmic decaheme cytochrome (electron transfer protein) to harvest electrons from both soluble iron and poised electrodes. This complex has two unique characteristics: (i) it lacks an extracellular cytochrome c , and (ii) the periplasmic decaheme cytochrome c undergoes proteolytic cleavage to produce a functional electron transfer protein. These characteristics are conserved in phototrophs harboring homologous proteins.
Yang Li, Han‐Qing Yu, Qiang Tang
Environmental Research · 2025
Junqi Zhang, Wenjing Lv, Yangyang Wang et al.
Chemical Engineering Journal · 2025
Suwon Kim, Ye Sun Han, Gaeun Lim et al.
Bioelectrochemistry · 2025
Namita P. Shroff, Shuai Xu, Julyana Acevedo et al.
Journal of The Electrochemical Society · 2017
Shewanella oneidensis MR-1 employs various methods of Extracellular Electron Transport (EET) to insoluble terminal electron acceptors, including graphite felt anodes of BioElectrochemical Systems (BESs). Fibers in the felt form a three dimensional meshwork within which microbes can form biofilms, as well as occupy the interstitial spaces as planktonic cells. Our results indicate that these interstices generated by the meshwork create a novel microenvironment where planktonic cells grow to higher density under certain conditions. When incubated anaerobically with 18 mM lactate and 30 mM fumarate, planktonic cell counts within the electrodes are ∼10-fold higher than bulk planktonic cell counts; a phenomenon we termed the "interstitial felt effect". Upon lowering both lactate and fumarate concentrations 10-fold, while bulk planktonic cell counts are stable, the interstitial felt effect disappears. This effect reappears when lactate and fumarate concentrations are lowered another 10-fold. Cyclic voltammetry experiments did not reveal any modification of the graphite fibers within the electrodes. A mutant strain lacking the primary flavin transporter gene, bfe, also expresses the interstitial felt effect. The interstitial planktonic microenvironment of electrically inert polyurethane sponge did not demonstrate this phenomenon. This study provides new insights into interactions of microbes with electrode materials that may help improve overall BES performance.
Keisuke Tomita, Atsumi Hirose, Yugo Tanaka et al.
Journal of Bioscience and Bioengineering · 2023
Edina Klein, Hannah Heintz, René Wurst et al.
Scientific Reports · 2024
Biofilm formation by Shewanella oneidensis has been extensively studied under oxic conditions; however, relatively little is known about biofilm formation under anoxic conditions and how biofilm architecture and composition can positively influence current generation in bioelectrochemical systems. In this study, we utilized a recently developed microfluidic biofilm analysis setup with automated 3D imaging to investigate the effects of extracellular electron acceptors and synthetic modifications to the extracellular polymeric matrix on biofilm formation. Our results with the wild type strain demonstrate robust biofilm formation even under anoxic conditions when fumarate is used as the electron acceptor. However, this pattern shifts when a graphite electrode is employed as the electron acceptor, resulting in biofilm formation falling below the detection limit of the optical coherence tomography imaging system. To manipulate biofilm formation, we aimed to express BpfG with a single amino acid substitution in the catalytic center (C116S) and to overexpress bpfA. Our analyses indicate that, under oxic conditions, overarching mechanisms predominantly influence biofilm development, rather than the specific mutations we investigated. Under anoxic conditions, the bpfG mutation led to a quantitative increase in biofilm formation, but both strains exhibited significant qualitative changes in biofilm architecture compared to the controls. When an anode was used as the sole electron acceptor, both the bpfA and bpfG mutations positively impacted mean current density, yielding a 1.8-fold increase for each mutation.
Lukas Kneuer, René Wurst, Johannes Gescher
Advances in biochemical engineering, biotechnology · 2024
Enze Zhou, Feng Li, Dawei Zhang et al.
Water Research · 2022
Megan C Gruenberg, Michaela A. TerAvest
Journal of Industrial Microbiology & Biotechnology · 2023
Shewanella oneidensis MR-1 is an electroactive bacterium that is a promising host for bioelectrochemical technologies, which makes it a common target for genetic engineering, including gene deletions and expression of heterologous pathways. Expression of heterologous genes and gene knockdown via CRISPRi in S. oneidensis are both frequently induced by β-D-1-thiogalactopyranoside (IPTG), a commonly used inducer molecule across many model organisms. Here, we report and characterize an unexpected phenotype; IPTG enhances the growth of wild-type S. oneidensis MR-1 on the sugar substrate N-acetylglucosamine (NAG). IPTG improves the carrying capacity of S. oneidensis growing on NAG while the growth rate remains similar to cultures without the inducer. Extracellular acetate accumulates faster and to a higher concentration in cultures without IPTG than those with it. IPTG appears to improve acetate metabolism, which combats the negative effect that acetate accumulation has on the growth of S. oneidensis with NAG. We recommend using extensive experimental controls and careful data interpretation when using both NAG and IPTG in S. oneidensis cultures.
Xiaoyu Yong, Yong-Qi Jiang, Chao Wang et al.
Journal of Environmental Management · 2024
Xinqi Guo, Chenhui Yang, Jiaqi Wu et al.
Journal of Power Sources · 2024
Huixing Wu, Lingyan Ding, Han Wang et al.
Chemical Engineering Journal · 2024
Oluwadamilola Oluwatoyin Hazzan, Collins Chimezie Elendu, Claude Kiki et al.
Biochemical Engineering Journal · 2024
Daobo Li, Xiaodan Zheng, Yonggang Yang et al.
ChemElectroChem · 2021
Abstract Natural microbes employing c ‐type cytochromes ( c ‐Cyts) for extracellular electron transport (EET) were greatly valuable to develop redox‐based bioelectrochemical applications. However, low levels of c ‐Cyt expression limited the phylogenetically diverse Gram‐positive species to be used in bioelectrochemical devices. This work reported the remarkable finding that a high level of c ‐Cyts was expressed in the cells of the Gram‐positive strain Lysinibacillus varians GY32. c ‐Cyts in Lysinibacillus varians GY32 cells were expressed at a level close to those in Shewanella oneidensis . These c ‐Cyts were found to cluster in cytoplasmic membrane and periplasmic space, along the length of Lysinibacillus varians GY32 cell. With voltammetry and spectroelectrochemical titration, phenazine methosulfate‐mediated electron transfer between the c ‐Cyts and an electrode was proved. These results expanded the accessible natural models of EET and suggested a new microbial platform for developing bioelectrochemical applications.
David Rehnlund, Guiyeoul Lim, Laura-Alina Philipp et al.
iScience · 2022
Extracellular electron transfer (EET) from microorganisms to inorganic electrodes is a unique ability of electrochemically active bacteria. Despite rigorous genetic and biochemical screening of the c -type cytochromes that make up the EET network, the individual electron transfer steps over the cell membrane remain mostly unresolved. As such, attempts to transplant entire EET chains from native into non-native exoelectrogens have resulted in inferior electron transfer rates. In this study we investigate how nanostructured electrodes can interface with Shewanella oneidensis to establish an alternative EET pathway. Improved biocompatibility was observed for densely packed nanostructured surfaces with a low cell-nanowire load distribution during applied external forces. External gravitational forces were needed to establish a bioelectrochemical cell-nanorod interface. Bioelectrochemical analysis showed evidence of nanorod penetration beyond the outer cell membrane of a deletion mutant lacking all outer membrane cytochrome encoding genes that was only electroactive on a nanostructured surface and under external force.
Ricardo Javier Vázquez, Samantha R. McCuskey, Glenn Quek et al.
Macromolecular Rapid Communications · 2022
Successful practical implementation of bioelectrochemical systems (BES) requires developing affordable electrode structures that promote efficient electrical communication with microbes. Recent efforts have centered on immobilizing bacteria with organic semiconducting polymers on electrodes via electrochemical methods. This approach creates a fixed biocomposite that takes advantage of the increased electrode's electroactive surface area (EASA). Here, it is demonstrated that a biocomposite comprising the water-soluble conjugated polyelectrolyte CPE-K and electrogenic Shewanella oneidensis MR-1 can self-assemble with carbon paper electrodes, thereby increasing its biocurrent extraction by ≈6-fold over control biofilms. A ≈1.5-fold increment in biocurrent extraction is obtained for the biocomposite on carbon paper relative to the biocurrent extracted from gold-coated counterparts. Electrochemical characterization revealed that the biocomposite stabilized with the carbon paper more quickly than atop flat gold electrodes. Cross-sectional images show that the biocomposite infiltrates inhomogeneously into the porous carbon structure. Despite an incomplete penetration, the biocomposite can take advantage of the large EASA of the electrode via long-range electron transport. These results show that previous success on gold electrode platforms can be improved when using more commercially viable and easily manipulated electrode materials.
Mohammad Kalantar, Mohammad Mahdi Mardanpour, Soheila Yaghmaei
Bioelectrochemistry · 2018
René Wurst, Edina Klein, Johannes Gescher
Biofilm · 2024
In bioelectrochemical systems (BES), biofilm formation and architecture are of crucial importance, especially for flow-through applications. The interface between electroactive microorganisms and the electrode surface plays an important and often limiting role, as the available surface area influences current generation, especially for poor biofilm forming organisms. To overcome the limitation of the available electrode surface, nanoparticles (NPs) with a magnetic iron core and a conductive, hydrophobic carbon shell were used as building blocks to form conductive, magnetic micropillars on the anode surface. The formation of this dynamic three-dimensional electrode architecture was monitored and quantified in situ using optical coherence tomography (OCT) in conjunction with microfluidic BES systems. By cyclic voltammetry the assembled three-dimensional anode extensions were found to be electrically conductive and increased the available electroactive surface area. The NPs were used as controllable carriers for the electroactive model organisms Shewanella oneidensis and Geobacter sulfurreducens , resulting in a 5-fold increase in steady-state current density for S. oneidensis , which could be increased 22-fold when combined with Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) aggregates. In the case of G. sulfurreducens , the steady-state current density was not increased, but was achieved four times faster. The study presents a controllable, scalable and easy-to-use method to increase the electrode surface area in existing BES by applying a magnetic field and adding conductive magnetic NPs. These findings can most likely also be transferred to other electroactive microorganisms.
Qing Xia, Xueqin Chen, Changhong Liu et al.
Nano Letters · 2021
Studies of electron transfer at the population level veil the nature of the cell itself; however, in situ probing of the electron transfer dynamics of individual cells is still challenging. Here we propose label-free structural color microscopy for this aim. We demonstrate that Shewanella oneidensis MR-1 cells show unique structural color scattering, changing with the redox state of cytochrome complexes in the outer membrane. It enables quantitatively and noninvasive studies of electron transfer in single microbial cells during bioelectrochemical activities, such as extracellular electron transfer (EET) on a transparent single-layer graphene electrode. Increasing the applied potential leads to the associated EET current, accompanied by more oxidized cytochromes. The high spatiotemporal resolution of the proposed method not only demonstrates the large diversity in EET activity among microbial cells but also reveals the subcellular asymmetric distribution of active cytochromes in a single cell. We anticipate that it provides a potential platform for further exploring the electron transfer mechanism of subcellular structure.
S. Sriram, Lars Alexander Olivan, Ryan J. White et al.
Electrochimica Acta · 2024
A range of biotechnological applications for converting electricity to fixed metabolic substrates is fuelling the study of cathodic bioelectrochemical systems. Shewanella oneidensis MR-1 has emerged as an important model system for extracellular electron uptake on cathodes, as many of the proteins involved in this process overlap with the organism's previously characterized extracellular electron transport machinery. However, there are still many questions surrounding the mechanics of electron uptake in Shewanella stemming largely from the challenge of quantifying biomass on electrode surfaces. This limits our understanding of the physiologic and kinetic constraints of electron uptake, as well as our ability to make meaningful comparisons across systems. To investigate the relationship between cathodic activity and biomass, we used a Shewanella oneidensis strain genetically modified with cell aggregation protein CdrAB behind a blue light-controlled promotor. Using blue light exposure to control cell deposition, we then investigated the relationship between cathodic activity and biomass. Electrochemical impedance spectroscopy (EIS) confirmed a decrease in biofilm impedance over a range of blue light exposures (i.e., 2 to 8 h). Consistent with previous results, after this timepoint, a drop-in electrochemical activity was observed, and impedances increased. For biofilms within the 2-8 h light exposure range, we observed a trend towards increased biological current consumption by quantifying the difference between pre and post kill currents. Comparing EIS data between pre and post kill experiments supported an increase in impedance post addition of killing agents and a trend towards the lowest biofilm impedances observed in the longest blue light exposed systems. Using an equivalent circuit model to extrapolate specific biofilm parameters we quantified the charger transfer resistance within the biofilm that corresponds to varying biofilm thicknesses and matches previously observed activities. For example, electrochemical activity was highest for the 8 h blue light exposed biofilm condition, with a maximum cathodic biologic current of -5.49 ± 0.85 µA, and a biofilm charge transfer resistance measured at 6909.5 ± 2136.5 Ω. On an individual reactor basis, we correlate this biofilm charge transfer resistance with biologic cathodic current. We observed a linear trend with a correlation score of 0.87 (r2 = 0.773). To the best of our knowledge, this is the first investigation of biofilm physiology on Shewanella cathodes using EIS. Continued efforts in this direction will further our understanding of biofilm-electrode interface during extracellular electron uptake with the goal of enhancing applications to bioelectrochemical systems.
Laura-Alina Philipp, Lukas Kneuer, Carina Mayer-Windhorst et al.
Applied and Environmental Microbiology · 2025
Research in electro-microbiology provides unique opportunities to study and exploit microbial physiology. Several efforts have been made to transplant the extracellular electron transport chain from the native exoelectrogenic model organism Shewanella oneidensis into Escherichia coli . However, systematic comparisons between donor and recipient strain configurations are largely missing. Hence, the proposed minimal protein set, consisting of the c -type cytochromes cytoplasmic membrane protein A (CymA), small tetraheme cytochrome (STC), MtrA, and MtrC, as well as the β -barrel protein MtrB, was heterologously expressed in E. coli in different expansion stages. These stages were compared to corresponding S. oneidensis strains in terms of anthraquinone-2,6-disulfonate (AQDS) and ferric citrate reduction rates. This revealed that transplantation of heterologous extracellular electron transfer (EET) chains is associated with a tremendous decrease in electron transfer rates. As the acquired electron transfer rates were not competitive to S. oneidensis , it was hypothesized that protein localization and maturation might be affected by heterologous expression. Hence, the type II secretion system from S. oneidensis was also transplanted into an E. coli strain. The latter allowed the secretion of the terminal reductase MtrC onto the cell surface of E. coli for the first time. This was correlated with significantly increased but still insufficient extracellular electron transfer rates. Further experiments suggest that the correct folding of MtrB might be a further bottleneck.IMPORTANCEResearch on transplanting extracellular electron transfer (EET) chains into non-native exoelectrogens is vital for advancing bioenergy and bioremediation technologies. Enabling these organisms to transfer electrons to external surfaces like anodes can enhance microbial fuel cell efficiency and electricity generation from organic waste. This approach can broaden the range of substrates and products for biotechnological applications, offering innovative solutions for sustainable production. Our work shows that transplanting the EET chain of Shewanella oneidensis into Escherichia coli is more complex than previously suggested. The heterologous expression of only c -type cytochromes and the β-barrel protein MtrB is insufficient for competitive reduction rates. Predominantly, MtrC and MtrB require specific proteins for transport and folding, necessitating co-expression and maturation. We could identify the type II secretion system of S. oneidensis as crucial for MtrC secretion in E. coli . Thereby, this work highlights the substrate specificity of bacterial type II secretion systems, suggesting methods to optimize protein production and secretion in bioelectrochemical applications.
Yixin Li, Dong Xia, Yong Xie et al.
Journal of the American Chemical Society · 2025
Microbial electrosynthesis (MES) offers a sustainable and low-carbon approach for CO 2 valorization, with Shewanella oneidensis ( S. oneidensis ) MR-1 identified as an ideal microbe for MES. However, no prior research has demonstrated that S. oneidensis MR-1 can directly metabolize CO 2 into multicarbon (C 2+ ) products due to its inability to perform the intracellular formate assimilation pathway. Here, we provide initial proof-of-concept evidence of direct bioelectrochemical CO 2 reduction to the C 4 product of malate. Specifically, the transformation of CO 2 to malate attains a notable production concentration of 1.18 mmol·L -1 , marking the first instance of direct C 4 compound bioelectrosynthesis. Such remarkable CO 2 -to-C 4 conversion performances are attributed to the successful implementation of dual-plasmid systems in S. oneidensis MR-1, which facilitate the overexpression of the reductive glycine pathway (Plasmid I) for assimilating CO 2 -derived formate and the alternative malate biosynthetic pathway (Plasmid II) to channel metabolic intermediates toward the biosynthesis of malate. Advancing CO 2 valorization toward carbon-negative C 2+ bioproducts, our sophisticated dual-plasmid systems engineered in microbes can be further refined for scalable CO 2 bioelectrolysis with the objective of facilitating industrial applications.
Yoshihide Tokunou, Hiromasa Tongu, Masanori Toyofuku et al.
Electrochemistry Communications · 2024
Flavin is one of the most prevalent redox molecules utilized by electroactive bacteria. Electroactive bacteria form a three-dimensional architecture with multiple cell assemblages on electrodes in bioelectrochemical systems. This provokes the importance of unveiling the redox chemistry of flavins during electron transfer not only at the bacteria/electrode interface but also inside cell assemblages. However, it has been difficult to directly compare the redox species contributing to each electron transfer reaction. In this study, to simultaneously detect the flavin redox species at the electrode surface and those in cell assemblages, we conducted bipotentiometric cyclic voltammetry on a colony of Shewanella oneidensis MR-1. The bipotentiometric data showed that flavin mononucleotide proceeds the redox cycle at − 0.43 V (vs. standard hydrogen electrode) in the MR-1 colony assignable to the semiquinone/hydroquinone redox cycle, which was supported by experiments with semiquinone scavenger and gene deletion mutants. Notably, the peak at − 0.43 V was not detected at the electrode surface, indicating that the flavin redox cycles and redox potentials involved in the electron transfer inside MR-1 assemblages differ from those at the MR-1/electrode interface. The measurement system presented herein offers a platform to clarify the redox reactions in cell assemblages as well as at the bacteria/electrode interface.