In-situ growth of graphene/polyaniline for synergistic improvement of extracellular electron transfer in bioelectrochemical systems

AbstractExtracellular electron transfer (EET) is a critical form of microbial metabolism that enables respiration on a variety of inorganic substrates, including metal oxides. For this reason, engineering EET processes has garnered significant interest for applications ranging from bioelectronics to materials synthesis. These applications require a strong understanding of electron flux from EET-relevant microbes. However, quantifying current generated by electroactive bacteria has been predominately limited to biofilms formed on electrodes, which require long incubation times, electrode colonization, and convolute contributions to EET from planktonic cells. To address this, we developed a platform for quantifying time-resolved EET flux from cell suspensions using aqueous dispersions of plasmonic tin-doped indium oxide nanocrystals. Tracking the change in optical extinction during electron transfer and fitting the optical response to a free electron model enabled quantification of current generation and electron transfer rate constants from planktonic Shewanella oneidensis cultures. Using this method, we differentiated between starved and actively respiring S. oneidensis, and between cells of varying genotype using an EET knockout strain. In addition, we quantified current production ranging from 0.12 – 0.68 fA • cell−1 from S. oneidensis cells engineered to differentially express a key EET gene using an inducible genetic circuit. Overall, our results validate the utility of colloidally stable plasmonic metal oxide nanocrystals as quantitative biosensors in native biological environments and contribute to a fundamental understanding of planktonic S. oneidensis electrophysiology using simple in situ spectroscopy.

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How thermophilic Gram-positive organisms perform extracellular electron transfer: characterization of the cell surface terminal reductase OcwA

10.1101/641308 ◽

2019 ◽

Author(s):

N.L. Costa ◽

B. Hermann ◽

V. Fourmond ◽

M. Faustino ◽

M. Teixeira ◽

...

Keyword(s):

Electron Transfer ◽

Cell Surface ◽

Electron Acceptors ◽

Added Value ◽

Extracellular Electron Transfer ◽

Bioelectrochemical Systems ◽

Positive Bacterium ◽

Gram Positive ◽

Evolutionary Pathway ◽

Structural And Functional Properties

AbstractExtracellular electron transfer is the key process underpinning the development of bioelectrochemical systems for the production of energy or added-value compounds. Thermincola potens JR is a promising Gram-positive bacterium to be used in these systems because it is thermophilic. In this paper we describe the structural and functional properties of the nonaheme cytochrome OcwA, which is the terminal reductase of this organism. The structure of OcwA, determined at 2.2Å resolution shows that the overall-fold and organization of the hemes are not related to other metal reductases and instead are similar to that of multiheme cytochromes involved in the biogeochemical cycles of nitrogen and sulfur. We show that, in addition to solid electron acceptors, OcwA can also reduce soluble electron shuttles and oxyanions. These data reveal that OcwA can take the role of a respiratory ‘swiss-army knife’ allowing this organism to grow in environments with rapidly changing availability of terminal electron acceptors without the need for transcriptional regulation and protein synthesis.ImportanceThermophilic Gram-positive organisms were recently shown to be a promising class of organisms to be used in bioelectrochemical systems for the production of electrical energy. These organisms present a thick peptidoglycan layer that was thought to preclude them to perform extracellular electron transfer (i.e. exchange catabolic electrons with solid electron acceptors outside of the cell). In this manuscript we describe the structure and functional mechanisms of the multiheme cytochrome OcwA, the terminal reductase of the Gram-positive bacterium Thermincola potens JR found at the cell surface of this organism. The results presented here show that this protein is unrelated with terminal reductases found at the cell surface of other electroactive organisms. Instead, OcwA is similar to terminal reductases of soluble electron acceptors. Our data reveals that terminal oxidoreductases of soluble and insoluble substrates are evolutionarily related, providing novel insights into the evolutionary pathway of multiheme cytochromes.

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Conduction-band edge dependence of carbon-coated hematite stimulated extracellular electron transfer of Shewanella oneidensis in bioelectrochemical systems

Bioelectrochemistry ◽

10.1016/j.bioelechem.2014.11.005 ◽

2015 ◽

Vol 102 ◽

pp. 29-34 ◽

Cited By ~ 25

Author(s):

Shungui Zhou ◽

Jiahuan Tang ◽

Yong Yuan

Keyword(s):

Electron Transfer ◽

Conduction Band ◽

Shewanella Oneidensis ◽

Band Edge ◽

Conduction Band Edge ◽

Extracellular Electron Transfer ◽

Bioelectrochemical Systems ◽

Carbon Coated

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Nanotechnology to rescue bacterial bidirectional extracellular electron transfer in bioelectrochemical systems

RSC Advances ◽

10.1039/c6ra04734c ◽

2016 ◽

Vol 6 (36) ◽

pp. 30582-30597 ◽

Cited By ~ 77

Author(s):

Shafeer Kalathil ◽

Deepak Pant

Keyword(s):

Electron Transfer ◽

Electrode Materials ◽

Extracellular Electron Transfer ◽

Bioelectrochemical Systems ◽

Nanostructured Electrode

Advanced nanostructured electrode materials largely improve the bacterial bidirectional extracellular electron transfer in bioelectrochemical systems.

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Intra/extracellular electron transfer for aerobic denitrification mediated by in-situ biosynthesis palladium nanoparticles

Water Research ◽

10.1016/j.watres.2020.116612 ◽

2021 ◽

Vol 189 ◽

pp. 116612

Author(s):

Yating Jia ◽

Danshi Qian ◽

Yuancai Chen ◽

Yongyou Hu

Keyword(s):

Electron Transfer ◽

Palladium Nanoparticles ◽

Extracellular Electron Transfer ◽

Aerobic Denitrification

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NADH dehydrogenases Nuo and Nqr1 contribute to extracellular electron transfer by Shewanella oneidensis MR-1 in bioelectrochemical systems

Scientific Reports ◽

10.1038/s41598-019-51452-x ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 4

Author(s):

Cody S. Madsen ◽

Michaela A. TerAvest

Keyword(s):

Electron Transfer ◽

Shewanella Oneidensis ◽

Extracellular Electron Transfer ◽

Growth Defect ◽

Bioelectrochemical Systems ◽

Terminal Electron Acceptor ◽

Nadh Dehydrogenases ◽

Level Of Understanding ◽

High Level

Abstract Shewanella oneidensis MR-1 is quickly becoming a synthetic biology workhorse for bioelectrochemical technologies due to a high level of understanding of its interaction with electrodes. Transmembrane electron transfer via the Mtr pathway has been well characterized, however, the role of NADH dehydrogenases in feeding electrons to Mtr has been only minimally studied in S. oneidensis MR-1. Four NADH dehydrogenases are encoded in the genome, suggesting significant metabolic flexibility in oxidizing NADH under a variety of conditions. A strain lacking the two dehydrogenases essential for aerobic growth exhibited a severe growth defect with an anode (+0.4 VSHE) or Fe(III)-NTA as the terminal electron acceptor. Our study reveals that the same NADH dehydrogenase complexes are utilized under oxic conditions or with a high potential anode. Our study also supports the previously indicated importance of pyruvate dehydrogenase activity in producing NADH during anerobic lactate metabolism. Understanding the role of NADH in extracellular electron transfer may help improve biosensors and give insight into other applications for bioelectrochemical systems.

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