Search Results (146)

Electroactive biofilms (EABs) are essential for the performance of bioelectrochemical systems (BESs), but their formation in Geobacter, critically on conductive pili and exopolysaccharides, limits application under conditions where these components are deficient. Herein, we investigated the restorative effects of exogenous flavin mononucleotide (FMN) on EAB formation and extracellular electron transfer (EET) in two defective mutants of Geobacter sulfurreducens: the pili-deficient PCAΔ1496 and exopolysaccharides-deficient PCAΔ1501. Results show that FMN significantly promoted biofilm thickness in PCAΔ1496 (250%) and PCAΔ1501 (33%), while boosting maximum current outputs by 175-fold and 317.7%, respectively. Spectroscopic and electrochemical analyses revealed that FMN incorporates into biofilms, binds to outer membrane c-type cytochromes (c-Cyts), and enhances electron exchange capacity. Differential pulse voltammetry further confirmed that FMN did not exist independently in the biofilm but bound to outer membrane c-Cyts as a cofactor. Collectively, exogenous FMN plays dual roles (electron shuttle and cytochrome-bound cofactor) in defective Geobacter EABs, effectively restoring biofilm formation and enhancing EET efficiency. This study expands the understanding of the formation mechanism of Geobacter EABs and provides a novel strategy for optimizing BES performance. Full article

Electron transfer (ET) is a foundational biogeochemical process in paddy soils, distinctively molded by alternating anaerobic-aerobic conditions from flooding-drainage cycles. Despite extensive research on heavy metal(loid) (denoted as “HM”, e.g., As, Cd, Cr, Hg) dynamics in paddies, ET has not been systematically synthesized as a unifying regulatory mechanism, and the trade-offs of ET-based mitigation strategies remain unclear. These critical gaps have drastically controlled HMs’ mobility, which further modulates bioavailability and subsequent accumulation in rice (Oryza sativa L., a staple sustaining half the global population), posing substantial food safety risks. Alongside progress in electroactive microorganism (EAM) research, extracellular electron transfer (EET) mechanism delineation, and soil electrochemical monitoring, ET’s role in orchestrating paddy soil HM dynamics has garnered unparalleled attention. This review explicitly focuses on the linkage between ET processes and HM biogeochemistry in paddy ecosystems: (1) elucidates core ET mechanisms in paddy soils (microbial EET, Fe/Mn/S redox cycling, organic matter-mediated electron shuttling, rice root-associated electron exchange) and their acclimation to flooded conditions; (2) systematically unravels how ET drives HM valence transformation (e.g., As(V) to As(III), Cr(VI) to Cr(III)), speciation shifts (e.g., exchangeable Cd to oxide-bound Cd), and mobility changes; (3) expounds on ET-regulated HM bioavailability by modulating soil retention capacity and iron plaque formation; (4) synopsizes ET-modulated HM accumulation pathways in rice (root uptake, xylem/phloem translocation, grain sequestration); (5) evaluates key factors (water management, fertilization, straw return) impacting ET efficiency and associated HM risks. Ultimately, we put forward future avenues for ET-based mitigation strategies to uphold rice safety and paddy soil sustainability. Full article

Magnetic biochars (MBCs) have been shown to inhibit the horizontal transfer of antibiotic resistance genes (ARGs) in soils, both with and without microplastics (MPs); however, the underlying molecular biological mechanisms remain unclear. This study examined the effects of MBCs and coexisting polybutylene adipate terephthalate microplastics (PBAT MPs) on the physiological characteristics of Serratia marcescens ZY01 (a host strain carrying the tet gene) and further investigated their relationships with the absolute abundance of the tet gene in soil. The results demonstrated that MBCs promoted prodigiosin synthesis in Serratia marcescens ZY01 by mediating the electron transfer process, the effect of which was further enhanced in the presence of PBAT MPs. In treatments without PBAT MPs, MBCs generally suppressed the production of both proteins and polysaccharides in the extracellular polymeric substances. In contrast, in treatments containing PBAT MPs, the protein content gradually decreased with decreasing iron-to-biochar ratios, while the polysaccharide content remained largely unchanged. MBCs also elevated intracellular ROS levels due to the increased oxidative stress, particularly in treatments with PBAT MPs. A positive correlation between intracellular ROS levels and cell membrane permeability indicates that intracellular ROS was the primary driver of the increased cell membrane permeability. The presence of MBCs and PBAT MPs generally provided favorable habitats for Serratia marcescens ZY01, thereby enhancing its cell viability. Mantel test analysis indicated that MBCs influenced Serratia growth in soil by modulating its cell viability. Furthermore, the increased intracellular ROS level was significantly positively correlated with the absolute abundance of the tet gene in soil, implying the horizontal transfer of the tet gene at the intra-genus level. These findings offer helpful insights for developing environmental remediation strategies based on biochar–iron composites. Full article

Choline is a central metabolite that connects membrane turnover, neurotransmission, and one-carbon metabolism, and its reliable measurement across diverse biological matrices remains a significant analytical challenge. This review brings together biological context, electrochemical mechanisms, and device engineering to define realistic performance targets for choline sensors in blood, cerebrospinal fluid, extracellular space, and milk. We examine enzymatic sensor architectures ranging from peroxide-based detection to mediated electron transfer via ferrocene derivatives, quinones, and osmium redox polymers and assess how applied potential, oxygen availability, and film structure shape electron-transfer pathways. Evidence for direct electron transfer with choline oxidase is critically evaluated, with emphasis on the essential controls needed to distinguish true flavin-based communication from peroxide-related artefacts. We also examine bienzymatic formats that allow operation at low or negative bias and discuss strategies for matrix-matched validation, selectivity, drift control, and resistance to fouling. To support reliable translation, we outline reporting standards that include matrix-specific concentration ranges, reference electrode notation, mediator characteristics, selectivity panels, and access to raw electrochemical traces. By connecting biological requirements to mechanistic pathways and practical design considerations, this review provides a coherent framework for developing choline sensors that deliver stable, reproducible performance in real samples. Full article

Electrical stimulation is increasingly explored as a strategy to accelerate the development of electroactive biofilms in microbial fuel cells (MFCs), yet its integration with photosynthetic MFCs (pMFCs) remains insufficiently understood. This study evaluated how short-term anodic stimulation (0.5–5 V, 4 days) affects biofilm formation and COD removal, and how subsequent operation with photosynthetic cathodes—Chlorella sp., Arthrospira platensis and Tetraselmis subcordiformis—modulates anodic microbial communities and functional potential. Stimulation at 1 V yielded the best activation effect, resulting in the highest voltage output, power density and fastest COD removal kinetics, whereas 5 V inhibited biofilm development. During pMFC operation, Chlorella produced the highest voltage (0.393 ± 0.064 V), current density (0.14 ± 0.02 mA·cm⁻²) and Coulombic efficiency (~19%). Arthrospira showed moderate performance, while Tetraselmis generated no current despite efficient COD removal. 16S rRNA sequencing revealed distinct cathode-driven community shifts: Chlorella enriched facultative electroactive taxa, Arthrospira promoted sulfur-cycling bacteria and Actinobacteria, and Tetraselmis induced strong methanogenic dominance. Functional prediction and qPCR confirmed these trends, with Chlorella showing increased pilA abundance and Tetraselmis displaying enriched methanogenic pathways. Overall, the combined use of optimal anodic stimulation and photosynthetic cathodes demonstrates that cathodic microalgae strongly influence anodic redox ecology and energy recovery, with Chlorella-based pMFCs offering the highest electrochemical performance. Full article

The green synthesis of silver nanoparticles (AgNPs) by bacteria is a strategic route for sustainable nanobiotechnology; however, the genomic and biochemical mechanisms that make it possible remain poorly defined. In this study, bacteria native to silver-bearing mine tailings in Taxco (Mexico) were isolated, capable of tolerating up to 5 mM of AgNO₃ and producing extracellular AgNPs. Spectroscopic (430–450 nm) and structural (XRD, fcc cubic phase) characterization confirmed the formation of AgNPs with average sizes of 17–21 nm. FTIR evidence showed the participation of extracellular proteins and polysaccharides as reducing and stabilizing agents. Genomic analyses assigned the isolates as Lysinibacillus fusiformis 31HCl and L. xylanilyticus G1-3. Genome mining revealed extensive repertoires of genes involved in uptake, transport, efflux and detoxification of metals, including P-type ATPases, RND/ABC/CDF transporters, Fe/Ni/Zn uptake systems, and metal response regulators. Notably, homologues of the silP gene, which encode Ag⁺ translocator ATPases, were identified, suggesting convergent adaptation to silver-rich environments. Likewise, multiple nitroreductases (YodC, YdjA, YfKO) were detected, candidates for mediating electron transfer from NAD(P)H to Ag⁺. These findings support the role of Lysinibacillus as microbial nanofactories equipped with specialized molecular determinants for silver tolerance and AgNP assembly, providing a functional framework for microorganism-based nanobiotechnology applications. Full article

Microbial electrolysis cells (MECs) are bioreactors that utilize electroactive microorganisms to catalyze the oxidation of organic substrates in wastewater, generating electron flow for hydrogen production. Despite the concept, a persistent performance gap exists where metabolically active anodic biofilms frequently fail to achieve expected current densities by the flow of electrons to produce hydrogen. This review examines the multiple causes that lead to the disconnect between robust biofilm development, electron transfer, and hydrogen production. Factors affecting biofilm generation (formation, substrate selection, thickness, conductivity, and heterogeneity) are discussed. Moreover, factors affecting electron transfer (electrode configuration, mass transfer constraints, key electroactive species, and metabolic pathways) are discussed. Also, substrate diffusion limitations, proton accumulation causing inhibitory pH gradients in stratified biofilms, elevated internal resistance, electron diversion to competing processes like hydrogenotrophic methanogenesis consuming H₂, and detrimental biofilm aging, impacting hydrogen production, are studied. The critical roles of electrode materials, reactor configuration, and biofilm electroactivity are analyzed, emphasizing advanced electrochemical (CV, EIS, LSV), imaging (CLSM, SEM, AFM), and omics (metagenomics, transcriptomics, proteomics) techniques essential for diagnosing bottlenecks. Strategies to enhance extracellular electron transfer (EET) (advanced nanomaterials, redox mediators, conductive polymers, bioaugmentation, and pulsed electrical operation) are evaluated for bridging this performance gap and improving energy recovery. The review presents an integrated framework connecting biofilm electroactivity, EET kinetics, and hydrogen evolution efficiency. It highlights that conventional biofilm metrics may not reflect actual electron flow. Combining electrochemical, microelectrode, and omics insights allows precise evaluation of EET efficiency and supports sustainable MEC optimization for enhanced hydrogen generation. Full article

The emergence of multidrug-resistant Staphylococcus aureus underscores the urgent need for novel therapeutic agents targeting essential bacterial pathways. The lipoteichoic acid synthase (LtaS) is crucial for the synthesis of lipoteichoic acid in the cell wall of Gram-positive bacteria and represents a promising and vulnerable target for antimicrobial drug development. This study employed a comprehensive computational pipeline to identify potent inhibitors of the LtaS enzyme. A library of natural compounds was retrieved from the COCONUT database and screened against the crystal structure of the extracellular domain of LtaS (eLtaS) (PDB ID: 2W5R, obtained from the Protein Data Bank) through a multi-stage molecular docking strategy. This process started with High-Throughput Virtual Screening (HTVS), followed by Standard Precision (SP) docking, and culminated in Extra Precision (XP) docking to refine the selection of hits. The top-ranking compounds from XP docking were subsequently subjected to MM-GBSA binding free energy calculations for further filtration. The stability and dynamic behavior of the resulting candidate complexes were then evaluated using 100 ns molecular dynamics (MD) simulations, which confirmed the structural integrity and binding stability of the ligands. Density Functional Theory calculations revealed that screened ligands exhibit improved electronic stabilization and charge-transfer characteristics compared to a reference compound, suggesting enhanced reactivity and stability relevant for hit identification. Finally, ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) profiling was conducted to assess the drug-likeness and pharmacokinetic safety of the lead compounds. These findings support them as promising orally active leads for further optimization. Our integrated approach shortlisted eight initial hits (A–H) that showed interesting scaffold diversity and finally identified two compounds, herein referred to as Compound A and Compound B, which demonstrated stable binding, favorable free energy, and an acceptable Absorption, Distribution, Metabolism, and Excretion, and Toxicity (ADMET) profile. These candidates emerge as promising starting points for developing novel anti-staphylococcal agents targeting the LtaS enzyme that cand be further proved by experimental validation. Full article

Dark fermentative hydrogen production is constrained by challenges including low hydrogen yield and operational instability. Magnetic nanoparticles (MNPs) have emerged as promising additives for enhancing biohydrogen production due to their unique physicochemical characteristics, such as high specific surface area, excellent electrical conductivity, and inherent magnetic recyclability. This review systematically compares the enhancement mechanisms of MNPs in two distinct microbial systems: pure cultures and mixed cultures. In pure cultures, MNPs function primarily at the cellular and molecular levels through the following: (1) serving as sustained-release sources of essential metallic cofactors like Fe and Ni to promote hydrogenase synthesis and activation; (2) acting as efficient electron carriers that facilitate intracellular and extracellular electron transfer; and (3) redirecting central carbon metabolism toward high-hydrogen-yield acetate-type fermentation. In mixed cultures, which are more representative of practical applications, MNPs operate at the ecological level through the following: (1) modifying microenvironmental niches to exert selective pressure that enriches hydrogen-producing bacteria, such as Clostridium; (2) forming conductive networks that promote direct interspecies electron transfer and strengthen syntrophic metabolism; and (3) enhancing system robustness via toxin adsorption and pH buffering. Despite promising phenomenological improvements, critical knowledge gaps remain, including unclear structure–activity relationships of MNPs, insufficient quantification of electron transfer pathways, unknown genetic regulatory mechanisms, and overlooked magnetobiological effects. Future research should integrate electrochemical monitoring, multi-omics analyses, and advanced characterization techniques to deepen the mechanistic understanding of nanomaterial–microbe interactions. This review aims to provide theoretical insights and practical strategies for developing efficient and sustainable MNP–microorganism hybrid systems for scalable biohydrogen production. Full article

High-nitrogen organic chemical wastewater is characterized by high chemical oxygen demand (COD_Cr), poor biodegradability, and toxic nitrogenous organics, posing significant challenges for conventional biological treatment. In this study, a dual-electrical treatment strategy integrating an electromagnetic Fenton (EM-Fenton) pretreatment unit with a three-dimensional biofilm electrode reactor (3D-BER) is proposed. The EM-Fenton system used iron–carbon fillers under electric and magnetic fields to generate hydroxyl radicals (·OH), enabling efficient oxidation of nitro-aromatic compounds and the conversion of organic nitrogen into NO₃⁻-N, while reducing Fe²⁺ input and iron sludge generation. Subsequently, the 3D-BER, filled with Fe₃O₄/Mn₃O₄-modified polyurethane spheres, facilitated autotrophic denitrification and phosphorus removal through enhanced extracellular electron transfer and trace hydrogen (H₂) release. Experimental results demonstrated that the EM-Fenton system achieved COD_Cr and NH₄⁺ removal rates of over 40% and 14%, respectively, under optimal HRT. The 3D-BER further improved removal efficiencies, with TN and TP reductions exceeding 80% and 81%, respectively, significantly outperforming the control groups. Microbial analysis revealed the enrichment of functional genera, such as Pararhodobacter and Thauera, and the upregulation of key denitrification pathways. This coupled system demonstrated high treatment efficiency, process synergy, and microbial selectivity, offering a promising approach for the advanced treatment of high-nitrogen industrial wastewater. Full article

This study looked at a fungal–cyanobacterial co-pellet system for cleaning up coffee waste and producing high-value polymers. Optimization focused on the pelletization process, waste removal efficiency, and biomass yield. Optimal conditions, including pH (6.5), glucose concentration (6 g/L), and shaking speed (130 rpm), achieved a maximum cyanobacterial immobilization efficiency of up to 97% on the fungal mycelium. Scanning electron microscopy (SEM) confirmed the formation of an integrated co-pellet structure, with fungal hyphae acting as a physical scaffold and extracellular polymeric substances (EPSs) enhancing cell–cell adhesion. The co-culture system exhibited superior performance compared to fungal (20.56 g/L) and algal (1.09 g/L) monocultures. It effectively removed major coffee effluent pollutants, achieving a significant reduction in total phenolic compounds (74.5%). Furthermore, the co-pellets displayed a remarkable final biomass yield (24.33 g/L) and high production of extracellular polymeric substances (EPSs) (5.28 g/L) and intracellular polymeric substances (IPSs) (3.84 g/L). The synergistic relationship was further confirmed by high nitrogen contents in the co-pellets (15.24%), which significantly surpassed that of the individual fungal biomass, suggesting interspecies nutrient transfer. Valuable glycerol-lipids were detected and identified in the fermentative broth of the co-culture confirming a highly efficient bioconversion process. Analyses revealed a targeted metabolic flow toward the accumulation of monoglycerides, notably monooleoylglycerol and monopalmitin, highlighting a powerful cooperative compatibility for producing high-value emulsifiers. Overall, these findings firmly establish the cyano-fungal co-pellet system as a robust and sustainable biorefinery approach for treating complex industrial wastewater while producing a high-quality, value-added biomass suitable for utilization as a biofertilizer or animal feed. Full article

Hexavalent chromium (Cr(VI)) is a highly toxic and carcinogenic pollutant commonly found in industrial wastewater. To address the challenge of sulfate inhibition on biological methods for treating chromium-containing wastewater, this study investigated the enhancement effect and mechanism of anthraquinone-2,6-disulfonate (AQDS) on the anaerobic bio-reduction of Cr(VI). At an AQDS dosage of 30 mg/L, Cr(VI) reduction efficiency increased by 7.8-fold compared to the group with only sulfate. AQDS demonstrated remarkable performance of Cr(VI) bio-reduction by reducing intracellular Cr(VI) penetration, lowering reactive oxygen species (ROS) levels, and maintaining optimal NADH/NAD⁺ ratios. Importantly, AQDS restores Cr(VI) reduction efficiency by directing electron flow toward Cr(VI) reduction through enhanced extracellular electron transfer, thereby mitigating the competitive inhibitory effect of sulfate. It concluded that AQDS effectively enhances Cr(VI) bio-reduction, offering a promising strategy for the environmental remediation of Cr(VI)-contaminated wastewater under sulfate-rich conditions. Full article

Microbial remediation of chromium-contaminated soil through extracellular electron transfer is an economical and environmentally friendly strategy. Exogenous quorum sensing (QS) signaling molecules could facilitate the process of electron transport. However, it remains unclear whether regulating QS could enhance the microbial remediation effect. In this study, exogenous N-acylated-L-homoserine lactones (AHLs) were added for the remediation of Cr(VI)-contaminated soil by S. putrefaciens. Various AHLs such as C8-HSL, C10-HSL, 3OC8-HSL, 3OC10-HSL and 3OC12-HSL were detected in the remediation, with the concentrations of 5.91 ng/L, 1.09 ng/L, 4.10 ng/L, 2.29 ng/L and 24.51 ng/L. The addition of C10-HSL and 3OC12-HSL significantly promoted the Cr(VI) reduction rates by 11.25% and 9.20%. There were also various AHLs in the Cr(VI) reduction by indigenous microorganisms. The AHLs species measured and their concentrations were C8-HSL (5.05 ng/L), C10-HSL (3.27 ng/L), C12-HSL (0.11 ng/L), 3OC8-HSL (0.11 ng/L), 3OC10-HSL (0.05 ng/L), and 3OC12-HSL (2.92 ng/L). Relative to the untreated control, supplementation with C8-HSL, C12-HSL, and 3OC12-HSL produced significant enhancements in the Cr(VI) reduction rates by 4.10%, 3.05%, and 2.24%, respectively (p < 0.05). Comparing the effects of AHL on the remediation by S. putrefaciens and indigenous microorganisms, it could be found that C10-HSL enhanced the remediation effect by increasing the reduction rates of S. putrefaciens, and 3OC12-HSL enhanced the remediation effect by increasing the reduction rates of indigenous microorganisms. This study introduces a distinctive pathway for the promotion of the microbial remediation effect and contributes to further understanding the communication mechanism between exogenous and indigenous microorganisms. Full article

This study discussed the influence of acetate and sodium chloride concentration on monitoring 2,4-dichlorophenol(2,4-DCP) by electroactive bacteria. The performance of the reactor was represented by power density, and the electrochemical activity was represented by redox capacity. At the same time, micro-electrodes were used to detect the redox potential between biofilms, and the changes in extracellular polymers and microbial community structure under different conditions were also explored. With acetate concentration of 1 g/L and sodium chloride concentration of 0.0125 g/L, the electroactive microorganisms were more sensitive to toxic substances and responded fast. The biofilm also evenly covered on the surface of the carrier, which aided in the diffusion of substances. Although the maximum power density monotonically increased with acetate concentration, high concentration of substrate may mask the inhibitory effect and affect the judgment of inhibitory results. The content of protein and polysaccharide increased monotonically with sodium chloride concentration. However, more polysaccharides would lead to high resistance to electron transfer. Compared to sodium chloride, the microbial content was more affected by acetate. The electroactive microorganisms had strong adaptability to salinity. In practical application, it is conducive to increase the sensitivity of MFCs to reasonably reduce the concentration of acetic acid and sodium chloride. Full article

Improving the anaerobic digestion (AD) of swine manure is crucial for sustainable waste-to-energy systems, given its high organic load and process instability risks. This study examined the combined effects of substrate-to-inoculum ratio (SIR, 0.1–3.2) and magnetite-mediated direct interspecies electron transfer on biogas production, effluent quality, and microbial community dynamics. The highest methane yield (262 ± 10 mL CH₄/g COD) was obtained at SIR 0.1, while efficiency declined at higher SIRs due to acid and ammonia accumulation. Magnetite supplementation significantly improved methane yield (up to a 54.1% increase at SIR 0.2) and reduced the lag phase, particularly under moderate SIRs. Effluent characterization revealed that low SIRs induced elevated soluble COD (SCOD) levels, attributed to microbial autolysis and extracellular polymeric substance release. Furthermore, magnetite addition mitigated SCOD accumulation and shifted molecular weight distributions toward higher fractions (>15 kDa), indicating enhanced microbial activity and structural polymer formation. Microbial analysis revealed that magnetite-enriched Syntrophobacterium and Methanothrix promoted syntrophic cooperation and acetoclastic methanogenesis. Diversity indices and PCoA further showed that both SIR and magnetite significantly shaped microbial structure and function. Overall, an optimal SIR range of 0.2–0.4 under magnetite addition provided a balanced strategy for enhancing methane recovery, effluent quality, and microbial stability in swine manure AD. Full article