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[Display omitted] • S. oneidensis MR-1 accelerates the corrosion of NF to form metal hydroxides in presence of Fe3+. • The product shows improved OER activity with an overpotential of 0.265 V at 10 mA cm−2. • Ni nanoparticles are synthesized for the first time by reduction of Ni2+ using S. oneidensis MR-1. Shewanella oneidensis is a facultative anaerobe with the ability to use different terminal electron donors and acceptors. Therefore, S. oneidensis can be used either as an oxidizing agent for microbial corrosion of metals or as a reducing agent for microbial synthesis of metal nanoparticles depending on the metal type. Herein, we have shown that S. oneidensis MR-1 can be used for both microbial corrosion of nickel foam (NF) and microbial synthesis of Ni nanoparticles under environmentally benign conditions. It is found that S. oneidensis MR-1 can accelerate the corrosion process to form metal hydroxides on the surface of NF in the presence of Fe3+, and the obtained electrode shows improved electrocatalytic activity toward oxygen evolution reaction with an overpotential of 0.265 V to achieve a current density of 10 mA cm−2. However, the corrosion process of NF by S. oneidensis MR-1 is severely inhibited in the presence of Fe2+. In addition, aside from the corrosion process of NF, we have for the first time shown that Ni nanoparticles can be synthesized by the reduction of Ni2+ ions using S. oneidensis MR-1. The results show that the microbial energy metabolism of S. oneidensis MR-1 facilitates the electron transfer from electron-donating NF to the electron-accepting metal ions (Fe3+, Ni2+) across the microbes, coupling the corrosion process (Ni → Ni2+) and metal ions reductions (Fe3+ → Fe2+, Ni2+ → Ni), which demonstrates great potential for in-situ modification of electrode with microorganism and provides new avenue for electrode fabrication. [ABSTRACT FROM AUTHOR]

The photocatalyst-enzyme hybrid systems (PEHSs) provided a promising method for environmental remediation by simultaneously harnessing the power of solar-energy conversion and biocatalysis. However, the use of PEHSs for environmental remediation was restricted by a complicated synthesis and assembly process. This work explored a simple one-pot biomineralization approach to fabricate PEHS. It was found that the cytochrome enzyme could be directly self-assembled onto the biosynthesized CdS during biomineralization by Shewanella oneidensis MR-1. More strikingly, those attached cytochrome enzymes could efficiently receive the photoelectrons from the CdS and serve as the photoreduction center which formed a typical PEHS. Impressively, this bio-CdS-cytochrome PEHS exhibited an extremely high photocatalytic decolorization rate of 69.4 mg/g/min, which was the highest record ever reported for procion red H-E3B. This work provided a simple and facile approach for PEHSs fabrication, which would be promising for practical application in environmental remediation. [Display omitted] • New approach for photocatalyst-enzyme hybrid system (PEHS) fabrication was explored. • The PEHS exhibited extremely high photocatalytic decolorization efficiency. • The cytochrome enzyme played key role on photocatalysis of PEHS. • The highest photo-decolorization rate of procion red H-E3B was obtained. [ABSTRACT FROM AUTHOR]

• The combination of natural microbe species enhanced both direct and indirect electron transport mechanisms. • The alliance system expands the utilization spectra of the carbon source. • Riboflavin and Phenazine two electron shuttles work in coordination. Microbial fuel cells with mixed bacteria always show better power output capacity than those with single bacteria due to synergetic effects between species. Here, a rational-designed synthetic three-species alliance system based on Shewanella oneidensis MR-1 (the model exoelectrogen), Pseudomonas aeruginosa, and Lactobacillus plantarum was constructed upon process optimization, the three-species alliance system in MFC delivered a maximum power density of ∼ 207 mW/m2 by using the glucose as the substrate, which was 2 ∼ 58 times higher than that of MFC inoculated with single species. In addition, the synthetic alliance system could generate electricity from broad substrate spectrum (lactose, saccharose, maltose, arabinose, cellobiose) with enhanced performance. Electrochemical and metabolism analysis indicated inter-species synergetic enhancement on charge transfer, substrate utilization, and biofilm formation was the underlying mechanism for performance improvement in MFC by this synthetic alliance system. In this system, L. plantarum uses glucose to produce lactic acid as the electrogenic substrate and electron donor of S. oneidensis MR-1, and P. aeruginosa uses glucose to produce another electron shuttle phenazine, which can also promote the growth of S. oneidensis MR-1 biofilm and help the alliance system to transfer electrons better. This work demonstrated a new strategy to enhance the MFC performance with a rational designed synthetic bacterial community, which would further renew the toolbox for MFC optimization. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) macroporous reduced graphene oxide/polypyrrole (rGO/Ppy) hydrogel assembled by bacterial cells was fabricated and applied for microbial fuel cells. By taking the advantage of electroactive cell-induced bioreduction of graphene oxide and in-situ polymerization of Ppy, a facile self-assembly by Shewanella oneidensis MR-1and in-situ polymerization approach for 3D rGO/Ppy hydrogel preparation was developed. This facile one-step self-assembly process enabled the embedding of living electroactive cells inside the hydrogel electrode, which showed an interconnected 3D macroporous structures with high conductivity and biocompatibility. Electrochemical analysis indicated that the self-assembly of cell-embedding rGO/Ppy hydrogel enhanced the electrochemical activity of the bioelectrode and reduced the electron charge transfer resistance between the cells and the electrode. Impressively, extremely high power output of 3366 ± 42 mW m−2 was achieved from the MFC with cell-embedding rGO/Ppy hydrogel rGO/Ppy, which was 8.6 times of that delivered from the MFC with bare electrode. Further analysis indicated that the increased cell loading by the hydrogel and improved electrochemical activity by the rGO/Ppy composite would be the underlying mechanism for this performance improvement. This study provided a facile approach to fabricate the biocompatible and electrochemical active 3D nanocomposites for MFC, which would also be promising for performance optimization of various bioelectrochemical systems. [Display omitted] • Cell-embedding rGO/Ppy hydrogel was assembled by bacterial cells. • The biohydrogel showed high cell viability and excellent electrochemical activity. • Efficient extracellular electron transfer between cell and electrode was achieved. • Extremely high power output of 3366 ± 42 mW m−2 was achieved from the MFC. [ABSTRACT FROM AUTHOR]

Whole-cell biosensors are an important class of analytical tools that offer the advantages of low cost, facile operation, and unique reproduction/regeneration ability. However, it has always been quite challenging to expand the sensing spectrum of the host. Here, a new approach to extend the cell sensing spectrum with biomineralized nanoparticles is developed. The nano-biohybrid design comprise biomineralized FeS nanoparticles firmly anchored onto the bacterium, Shewanella oneidensis MR-1, wherein the nanoparticles are wired to the cellular electron transfer machinery (MtrCAB/OmcA) of the bacterium, forming an artificial cyborgian redox machinery consisting of FeS-MtrCAB/OmcA-FccA. Strikingly, with this cyborgian redox machinery, the sensing spectrum of FeS hybridized S. oneidensis MR-1 cell is successfully expanded to enable whole-cell electrochemical detection of Vitamin B12, while an unhybridized native cell is incapable of sensing. This proof-of-concept nano-biohybrid design offers a new perspective on manipulating the microbial toolkit for an expanded sensing spectrum in whole-cell biosensors. [Display omitted] • A nano-hybridized electroactive bacteria based system was assembled. • Artificial cyborgian redox machinery was identified in this biohybrid cell. • This cyborgian redox machinery expanded the sensing spectrum of Shewanella cell. • A sensitive whole-cell biosensing system for VB12 was developed. [ABSTRACT FROM AUTHOR]

A novel whole-cell electrochemical sensor was developed and applied for sensitive amperometric detection of riboflavin. In this work, a whole-cell based riboflavin redox cycling system was characterized, in which electroactive bacteria Shewanella oneidensis MR-1 was employed as the biocatalyst to regenerate the reduced riboflavin after the electrode oxidation. This redox cycling system efficiently enhanced the electrochemical response of riboflavin and enabled a stable current output at poised electrode potential. Thus, a sensitive amperometric biosensing system for riboflavin detection was developed by integrating this whole-cell redox cycling system with the conventional riboflavin electrochemical sensor. Remarkably, this riboflavin biosensor exhibited high sensitivity (LOD = 0.85 ± 0.09 nM, S/N = 3), excellent selectivity and stability. Additionally, reliable analysis of real samples (food and pharmaceutical samples) by this biosensor was achieved. This work provided sensitive and practical tool for riboflavin detection, and demonstrated that the integration of electroactive bacteria and using its outwards electron transfer for redox cycling would be a powerful and promising strategy to improve the performance of electrochemical sensing system. [ABSTRACT FROM AUTHOR]

Although microbial fuel cells (MFCs) is considered as one of the most promising technology for renewable energy harvesting, low power output still accounts one of the bottlenecks and limits its further development. In this work, it is found that Cu 2+ (0.1 μg L −1 –0.1 mg L −1 ) or Cd 2+ (0.1 μg L −1 –1 mg L −1 ) significantly improve the electricity generation in MFCs. The maximum power output achieved with trace level of Cu 2+ (∼6 nM) or Cd 2+ (∼5 nM) is 1.3 times and 1.6 times higher than that of the control, respectively. Further analysis verifies that addition of Cu 2+ or Cd 2+ effectively improves riboflavin production and bacteria attachment on the electrode, which enhances bacterial extracellular electron transfer (EET) in MFCs. These results unveil the mechanism for power output enhancement by Cu 2+ or Cd 2+ addition, and suggest that metal ion addition should be a promising strategy to enhance EET as well as power generation of MFCs. [ABSTRACT FROM AUTHOR]