Increased biofilm in Shewanella oneidensis MR-1 leads to higher current generation in METs

2020 ◽  
Author(s):  
Ana V. Silva ◽  
Miriam Edel ◽  
Johannes Gescher ◽  
Catarina M. Paquete
Keyword(s):  
Biofilm Formation ◽  
Large Scale ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Central Process ◽  
Current Generation ◽  
Promising Alternative ◽  
Over Expression ◽  
Current Production ◽  
Low Levels

<p>Biofilm formation is a central process in the function of Microbial Electrochemical Technologies (METs). These technologies have emerged in recent years as a promising alternative green source of energy, in which microbes consume organic matter to produce energy or valuable by-products. It is the ability of performing extracellular electron transfer that allows these microbes, called electroactive organisms, to exchange electrons with an electrode in these systems. The low levels of current achieved have been the set-back for the large-scale application of METs. <em>Shewanella oneidensis</em> MR-1 is one of the most studied electroactive organisms, and it has been demonstrated that its increased biofilm formation can lead to higher current generation. The <em>bolA</em> gene has been identified as a central player in biofilm formation in different organisms, with its overexpression leading to increased biofilm production. In this work, we explored the effect of this gene in biofilm formation and current production by <em>S. oneidensis</em> MR-1. Our results demonstrate that this gene is involved in the biofilm formation by this organism, with its over expression leading to an increased biofilm formation. We could also show that this increase in biofilm formation lead to a consequent higher current generation. This information is a relevant step for the optimization of electroactive organisms towards their practical application in METs.</p>

scholarly journals Structures, Compositions, and Activities of Live Shewanella Biofilms Formed on Graphite Electrodes in Electrochemical Flow Cells

2017 ◽  
Vol 83 (17) ◽  
Author(s):  
Miho Kitayama ◽  
Ryota Koga ◽  
Takuya Kasai ◽  
Atsushi Kouzuma ◽  
Kazuya Watanabe
Keyword(s):  
Wastewater Treatment ◽  
Water Flow ◽  
Biofilm Formation ◽  
Shewanella Oneidensis ◽  
Flow Conditions ◽  
Current Generation ◽  
Content Type ◽  
Flow Cells ◽  
Electrode Potentials ◽  
Over Time

ABSTRACT An electrochemical flow cell equipped with a graphite working electrode (WE) at the bottom was inoculated with Shewanella oneidensis MR-1 expressing an anaerobic fluorescent protein, and biofilm formation on the WE was observed over time during current generation at WE potentials of +0.4 and 0 V (versus standard hydrogen electrodes), under electrolyte-flow conditions. Electrochemical analyses suggested the presence of unique electron-transfer mechanisms in the +0.4-V biofilm. Microscopic analyses revealed that, in contrast to aerobic biofilms, current-generating biofilm (at +0.4 V) was thin and flat (∼10 μm in thickness), and cells were evenly and densely distributed in the biofilm. In contrast, cells were unevenly distributed in biofilm formed at 0 V. In situ fluorescence staining and biofilm recovery experiments showed that the amounts of extracellular polysaccharides (EPSs) in the +0.4-V biofilm were much smaller than those in the aerobic and 0-V biofilms, suggesting that Shewanella cells suppress the production of EPSs at +0.4 V under flow conditions. We suggest that Shewanella cells perceive electrode potentials and modulate the structure and composition of biofilms to efficiently transfer electrons to electrodes. IMPORTANCE A promising application of microbial fuel cells (MFCs) is to save energy in wastewater treatment. Since current is generated in these MFCs by biofilm microbes under horizontal flows of wastewater, it is important to understand the mechanisms for biofilm formation and current generation under water-flow conditions. Although massive work has been done to analyze the molecular mechanisms for current generation by model exoelectrogenic bacteria, such as Shewanella oneidensis, limited information is available regarding the formation of current-generating biofilms over time under water-flow conditions. The present study developed electrochemical flow cells and used them to examine the electrochemical and structural features of current-generating biofilms under water-flow conditions. We show unique features of mature biofilms actively generating current, creating opportunities to search for as-yet-undiscovered current-generating mechanisms in Shewanella biofilms. Furthermore, information provided in the present study is useful for researchers attempting to develop anode architectures suitable for wastewater treatment MFCs.

scholarly journals Microbial Reduction of Metal-Organic Frameworks Enables Synergistic Chromium Removal

2018 ◽  
Author(s):  
Sarah K. Springthorpe ◽  
Christopher M. Dundas ◽  
Benjamin K. Keitz
Keyword(s):  
Metal Oxides ◽  
Metal Organic Frameworks ◽  
Reduction Rate ◽  
Shewanella Oneidensis ◽  
Particle Morphology ◽  
Microbial Reduction ◽  
Pollutant Removal ◽  
Extracellular Electron Transfer ◽  
Promising Alternative ◽  
Metal Organic

AbstractMicrobe-material redox interactions underpin many emerging technologies, including bioelectrochemical cells and bioremediation. However, commonly utilized material substrates, such as metal oxides, suffer from a lack of tunability and can be challenging to characterize. In contrast, metal-organic frameworks, a class of porous materials, exhibit well-defined structures, high crystallinity, large surface areas, and extensive chemical tunability. Here, we report that metal-organic frameworks can support the growth of the electroactive bacterium Shewanella oneidensis. Specifically, we demonstrate that Fe(III)-containing frameworks, MIL-100 and Fe-BTC, can be reduced by the bacterium via its extracellular electron transfer pathways and that reduction rate/extent is tied to framework structure, surface area, and particle morphology. In a practical application, we show that cultures containing S. oneidensis and reduced frameworks can remediate lethal concentrations of Cr(VI), and that pollutant removal exceeds the performance of either component in isolation or bioreduced iron oxides. Repeated cycles of Cr(VI) dosing had little effect on bacterial viability or Cr(VI) adsorption capacity, demonstrating that the framework confers protection to the bacteria and that no regenerative step is needed for continued bioremediation. In sum, our results show that metal-organic frameworks can serve as microbial respiratory substrates and suggest that they may offer a promising alternative to metal oxides in applications seeking to combine the advantages of bacterial metabolism and synthetic materials.

Molecular mechanisms regulating the catabolic and electrochemical activities of Shewanella oneidensis MR-1

2021 ◽  
Author(s):  
Atsushi Kouzuma
Keyword(s):  
Microbial Fuel Cells ◽  
Biofilm Formation ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Cellular Functions ◽  
Regulatory Systems ◽  
Electrochemically Active ◽  
Recent Developments

Abstract Electrochemically active bacteria (EAB) interact electrochemically with electrodes via extracellular electron transfer (EET) pathways. These bacteria have attracted significant attention due to their utility in environment-friendly bioelectrochemical systems (BESs), e.g. microbial fuel cells and electrofermentation systems. The electrochemical activity of EAB is dependent on their carbon catabolism and respiration; thus, understanding how these processes are regulated will provide insights into the development of a more efficient BES. The process of biofilm formation by EAB on BES electrodes is also important for electric current generation, because it facilitates physical and electrochemical interactions between EAB cells and electrodes. This article summarizes the current knowledge on EET-related metabolic and cellular functions of a model EAB, Shewanella oneidensis MR-1, focusing specifically on regulatory systems for carbon catabolism, EET pathways, and biofilm formation. Based on recent developments, the author also discusses potential uses of engineered S. oneidensis strains for various biotechnological applications.

Interfacing anoxic Shewanella oneidensis biofilms with electrically conducting nanostructures

2020 ◽  
Author(s):  
Edina Klein ◽  
René Wurst ◽  
David Rehnlund ◽  
Johannes Gescher
Keyword(s):  
Electron Transfer ◽  
Biofilm Formation ◽  
Electronic Communication ◽  
Shewanella Oneidensis ◽  
Model Organism ◽  
Laser Scanning Microscopy ◽  
Extracellular Electron Transfer ◽  
Metal Nanostructures ◽  
Special Importance ◽  
Anoxic Conditions

<p><em>Shewanella oneidensis</em> MR1 is the best understood model organism with regards to dissimilatory metal reduction and extracellular electron transfer onto carbon electrodes in bioelectrochemical systems (BES)<sup>1</sup>. However, under anoxic conditions <em>S. oneidensis</em> is known to form very thin biofilms resulting in low current density output. In contrast, another exoelectrogenic model organism <em>Geobacter surfurreduscens</em> can form electroactive biofilms up to 100 µm in thickness. This organism is known for its ability to transport electrons over a long range (> 10 µm) along a network of protein filaments, called microbial nanowires. Although still controversial, it was recently reported that OmcS has a special importance for the conductivity of these nanowires<sup>2</sup>. One of the key differences between <em>G. surfurreduscens</em> and <em>S. oneidensis</em> lies in how cell-to-cell electronic communication occurs, which dictate the range of electronic communication between distant cells. <em>S. oneidensis</em> relies on direct cell-to-cell communication via electron transfer between outer membrane cytochromes or via soluble redox active flavins that are secreted by the cells<sup>3</sup>. Our research is based on the question, what if the <em>S. oneidensis</em> biofilm formation could be improved by introducing an artificial electronic network, similar to the native microbial nanowires for <em>G. sulfurreducens</em>?</p> <p>We hypothesize that synthetic biofilms containing conductive nanostructure additives would allow <em>S. oneidensis</em> to build multilayer thick biofilms under anoxic conditions on solid electron acceptors. To answer this question of how conductive materials affect the formation of anoxic <em>S. oneidensis</em> biofilms, we integrated both biological and synthetic conductive nanostructures into these biofilms. As biological additive, the <em>c</em>-type cytochrome OmcS purified from<em> G. sulfurreducens</em> was utilized. As synthetic additives, both commercially available biotinylated gold nanorods and in-house electrochemically synthesized metal nanostructures were added to anoxic <em>S. oneidensis</em> biofilms.</p> <p>Cultivation and characterization of the biofilms was performed using our newly developed microfluidic bioelectrochemical platform. Microbial cultivation with the aid of microfluidic flow chambers has a great potential to form biofilms on an easy to handle laboratory scale with simultaneously ongoing multianalytical analysis<sup>4</sup>. In our bioelectrochemical microfluidic, system <em>S. oneidensis</em> biofilms can be grown under anoxic conditions using an anode as sole electron acceptor. The growth behavior and bioelectrochemical performance was evaluated by a combination of electrochemical techniques (chronoamperometry, electrochemical impedance spectroscopy, cyclic voltammetry) and optical analyses (confocal laser scanning microscopy and optical coherence tomography). The strategy of conductive nanostructured additives for improved electroactive biofilm formation could be an important tool for other exoelectrogenic microorganisms in order to exploit their physiological abilities for biotechnology.</p> <p>References:</p> <ol> <li>Beblawy, S. <em>et al</em>. (2018) <em>Molecular Microbiology</em> <strong>109</strong>: 571-583.</li> <li>Wang, F. <em>et al</em>. (2019) <em>Cell </em><strong>177</strong>: 361‐369.</li> <li>Shi, L. <em>et al</em>. (2016) <em>Nature Reviews Microbiology</em> <strong>14</strong>: 651-662.</li> <li>Hansen, S.H. <em>et al</em>. (2019) <em>Scientific Reports</em> <strong>9</strong>: 8933.</li> </ol> <p> </p>

scholarly journals Analyses of Current-Generating Mechanisms of Shewanella loihica PV-4 and Shewanella oneidensis MR-1 in Microbial Fuel Cells

2009 ◽  
Vol 75 (24) ◽  
pp. 7674-7681 ◽  
Author(s):  
Gregory J. Newton ◽  
Shigeki Mori ◽  
Ryuhei Nakamura ◽  
Kazuhito Hashimoto ◽  
Kazuya Watanabe
Keyword(s):  
Fuel Cells ◽  
Current Density ◽  
Microbial Fuel Cells ◽  
Mutational Analysis ◽  
Shewanella Oneidensis ◽  
Constant Current ◽  
Extracellular Electron Transfer ◽  
Planktonic Cells ◽  
Constant Current Density ◽  
Current Generation

ABSTRACT Although members of the genus Shewanella have common features (e.g., the presence of decaheme c-type cytochromes [c-cyts]), they are widely variable in genetic and physiological features. The present study compared the current-generating ability of S. loihica PV-4 in microbial fuel cells (MFCs) with that of well-characterized S. oneidensis MR-1 and examined the roles of c-cyts in extracellular electron transfer. We found that strains PV-4 and MR-1 exhibited notable differences in current-generating mechanisms. While the MR-1 MFCs maintained a constant current density over time, the PV-4 MFCs continued to increase in current density and finally surpassed the MR-1 MFCs. Coulombic efficiencies reached 26% in the PV-4 MFC but 16% in the MR-1 MFCs. Although both organisms produced quinone-like compounds, anode exchange experiments showed that anode-attached cells of PV-4 produced sevenfold more current than planktonic cells in the same chamber, while planktonic cells of MR-1 produced twice the current of the anode-attached cells. Examination of the genome sequence indicated that PV-4 has more c-cyt genes in the metal reductase-containing locus than MR-1. Mutational analysis revealed that PV-4 relied predominantly on a homologue of the decaheme c-cyt MtrC in MR-1 for current generation, even though it also possesses two homologues of the decaheme c-cyt OmcA in MR-1. These results suggest that current generation in a PV-4 MFC is in large part accomplished by anode-attached cells, in which the MtrC homologue constitutes the main path of electrons toward the anode.

scholarly journals High current production of Shewanella oneidensis with electrospun carbon nanofiber anodes is directly linked to biofilm formation

2021 ◽  
Author(s):  
Johannes Erben ◽  
Xinyu Wang ◽  
Sven Kerzenmacher
Keyword(s):  
Biofilm Formation ◽  
Anode Materials ◽  
Carbon Nanofiber ◽  
Fiber Diameter ◽  
Shewanella Oneidensis ◽  
Dry Mass ◽  
High Current ◽  
Steam Activation ◽  
Maximum Current ◽  
Current Production

1AbstractWe study the current production of Shewanella oneidensis MR-1 with electro-spun carbon fiber anode materials and analyze the effect of the anode morphology on the micro-, meso-and macroscale. The materials feature fiber diameters in the range between 108 nm and 623 nm, resulting in distinct macropore sizes and surface roughness factors. A maximum current density of (255± 71) µA cm−2 was obtained with 286 nm fiber diameter material. Additionally, micro-and mesoporosity were introduced by CO2 and steam activation which did not improve the current production significantly. The current production is directly linked to the biofilm dry mass under anaerobic and micro-aerobic conditions. Our findings suggest that either the surface area or the pore size related to the fiber diameter determines the attractiveness of the anodes as habitat and there-fore biofilm formation and current production. Reanalysis of previous works supports these findings.

Efficient Schedule of Energy-Constrained UAV Using Crowdsourced Buses in Last-Mile Parcel Delivery

2021 ◽  
Vol 5 (1) ◽  
pp. 1-23
Author(s):  
Yan Pan ◽  
Shining Li ◽  
Qianwu Chen ◽  
Nan Zhang ◽  
Tao Cheng ◽  
...  
Keyword(s):  
Traffic Congestion ◽  
Large Scale ◽  
Load Capacity ◽  
Scheduling Algorithm ◽  
Cost Effective ◽  
Promising Alternative ◽  
Logistics Industry ◽  
Last Mile ◽  
Delivery Scheduling ◽  
Schedule Approach

Stimulated by the dramatical service demand in the logistics industry, logistics trucks employed in last-mile parcel delivery bring critical public concerns, such as heavy cost burden, traffic congestion and air pollution. Unmanned Aerial Vehicles (UAVs) are a promising alternative tool in last-mile delivery, which is however limited by insufficient flight range and load capacity. This paper presents an innovative energy-limited logistics UAV schedule approach using crowdsourced buses. Specifically, when one UAV delivers a parcel, it first lands on a crowdsourced social bus to parcel destination, gets recharged by the wireless recharger deployed on the bus, and then flies from the bus to the parcel destination. This novel approach not only increases the delivery range and load capacity of battery-limited UAVs, but is also much more cost-effective and environment-friendly than traditional methods. New challenges therefore emerge as the buses with spatiotemporal mobility become the bottleneck during delivery. By landing on buses, an Energy-Neutral Flight Principle and a delivery scheduling algorithm are proposed for the UAVs. Using the Energy-Neutral Flight Principle, each UAV can plan a flying path without depleting energy given buses with uncertain velocities. Besides, the delivery scheduling algorithm optimizes the delivery time and number of delivered parcels given warehouse location, logistics UAVs, parcel locations and buses. Comprehensive evaluations using a large-scale bus dataset demonstrate the superiority of the innovative logistics UAV schedule approach.

scholarly journals Herbal Products and Their Active Constituents Used Alone and in Combination with Antifungal Drugs against Drug-Resistant Candida sp.

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 655
Author(s):  
Anna Herman ◽  
Andrzej Przemysław Herman
Keyword(s):  
Biofilm Formation ◽  
Fungal Infections ◽  
Antifungal Drugs ◽  
Membrane Transporters ◽  
Drug Resistant ◽  
Herbal Products ◽  
Active Constituents ◽  
Over Expression ◽  
Candida Sp ◽  
Current State

Clinical isolates of Candida yeast are the most common cause of opportunistic fungal infections resistant to certain antifungal drugs. Therefore, it is necessary to detect more effective antifungal agents that would be successful in overcoming such infections. Among them are some herbal products and their active constituents.The purpose of this review is to summarize the current state of knowledge onherbal products and their active constituents havingantifungal activity against drug-resistant Candida sp. used alone and in combination with antifungal drugs.The possible mechanisms of their action on drug-resistant Candida sp. including (1) inhibition of budding yeast transformation into hyphae; (2) inhibition of biofilm formation; (3) inhibition of cell wall or cytoplasmic membrane biosynthesis; (4) ROS production; and (5) over-expression of membrane transporters will be also described.

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