Extracellular Electron Shuttling Mediated by Soluble c-Type Cytochromes Produced by Shewanella oneidensis MR-1

2020 ◽  
Vol 54 (17) ◽  
pp. 10577-10587
Author(s):  
Tongxu Liu ◽  
Xiaobo Luo ◽  
Yundang Wu ◽  
John R. Reinfelder ◽  
Xiu Yuan ◽  
...  
Keyword(s):  
Shewanella Oneidensis ◽  
Electron Shuttling ◽  
Soluble C

scholarly journals Ferrihydrite associated organic matter (OM) stimulates reduction by <i>Shewanella oneidensis</i> MR-1 and a complex microbial consortia

2017 ◽  
Author(s):  
Rebecca E. Cooper ◽  
Karin Eusterhues ◽  
Carl-Eric Wegner ◽  
Kai Uwe Totsche ◽  
Kirsten Küsel
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Shewanella Oneidensis ◽  
Model Organism ◽  
Microbial Consortia ◽  
Rrna Gene ◽  
Natural Environments ◽  
Mineral Surfaces ◽  
Electron Shuttling ◽  
Reducing Conditions

Abstract. The formation of Fe(III) oxides in natural environments occurs in the presence of natural organic matter (OM), resulting in the formation of OM-mineral complexes that form through adsorption or coprecipitation processes. Thus, microbial Fe(III) reduction in natural environments most often occurs in the presence of OM-mineral complexes rather than pure Fe(III) minerals. In this study we investigated to which extent the content of adsorbed or coprecipitated OM on ferrihydrite influences the rate of Fe(III) reduction by Shewanella oneidensis MR-1, a model Fe(III)-reducing microorganism, in comparison to a microbial consortium extracted from the acidic, Fe-rich Schlöppnerbrunnen fen. We found that increased OM contents led to increased rates of microbial Fe(III) reduction by S. oneidensis MR-1 in contrast to earlier findings with the model organism Geobacter bremensis. Ferrihydrite-OM coprecipitates were reduced slightly faster than ferrihydrites with adsorbed OM. Surprisingly, the complex microbial consortia stimulated by a mixture of electrons donors (lactate, acetate, and glucose) mimics S. oneidensis under the same experimental Fe(III)-reducing conditions suggesting similar mechanisms of electron transfer whether or not the OM is adsorbed or coprecipitated to the mineral surfaces. We also followed potential shifts of the microbial community during the incubation via 16S rRNA gene sequence analyses to determine variations due to the presence of adsorbed or coprecipitated OM-ferrihydrite complexes in contrast to pure ferrihydrite. Community profile analyses showed no enrichment of typical model Fe(III)-reducing bacteria, such as Shewanella sp. or Geobacter sp., but an enrichment of fermenters (i.e. Enterobacteria) during pure ferrihydrite incubations which are known to use Fe(III) as an electron sink. Instead, OM-mineral complexes favored the enrichment of microbes including Desulfobacteria and Pelosinus sp., both of which can utilize lactate and acetate as an electron donor under Fe(III) reducing conditions. In summary, this study shows that increasing concentrations of OM in OM-mineral complexes determines microbial Fe(III) reduction rates and shapes the microbial community structure involved in the reductive dissolution of ferrihydrite. Similarities observed between the complex Fe(III)-reducing microbial consortia and the model Fe(III)-reducer S. oneidensis MR-1 suggest electron shuttling mechanisms dominate in OM-rich environments, including soils, sediments, and fens, where natural OM interacts with Fe(III) oxides during mineral formation.

scholarly journals Ferrihydrite-associated organic matter (OM) stimulates reduction by <i>Shewanella oneidensis</i> MR-1 and a complex microbial consortia

2017 ◽  
Vol 14 (22) ◽  
pp. 5171-5188 ◽  
Author(s):  
Rebecca Elizabeth Cooper ◽  
Karin Eusterhues ◽  
Carl-Eric Wegner ◽  
Kai Uwe Totsche ◽  
Kirsten Küsel
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Shewanella Oneidensis ◽  
Model Organism ◽  
Microbial Consortia ◽  
Rrna Gene ◽  
Natural Environments ◽  
Mineral Surfaces ◽  
Electron Shuttling ◽  
Reducing Conditions

Abstract. The formation of Fe(III) oxides in natural environments occurs in the presence of natural organic matter (OM), resulting in the formation of OM–mineral complexes that form through adsorption or coprecipitation processes. Thus, microbial Fe(III) reduction in natural environments most often occurs in the presence of OM–mineral complexes rather than pure Fe(III) minerals. This study investigated to what extent does the content of adsorbed or coprecipitated OM on ferrihydrite influence the rate of Fe(III) reduction by Shewanella oneidensis MR-1, a model Fe(III)-reducing microorganism, in comparison to a microbial consortium extracted from the acidic, Fe-rich Schlöppnerbrunnen fen. We found that increased OM content led to increased rates of microbial Fe(III) reduction by S. oneidensis MR-1 in contrast to earlier findings with the model organism Geobacter bremensis. Ferrihydrite–OM coprecipitates were reduced slightly faster than ferrihydrites with adsorbed OM. Surprisingly, the complex microbial consortia stimulated by a mixture of electrons donors (lactate, acetate, and glucose) mimics S. oneidensis under the same experimental Fe(III)-reducing conditions suggesting similar mechanisms of electron transfer whether or not the OM is adsorbed or coprecipitated to the mineral surfaces. We also followed potential shifts of the microbial community during the incubation via 16S rRNA gene sequence analyses to determine variations due to the presence of adsorbed or coprecipitated OM–ferrihydrite complexes in contrast to pure ferrihydrite. Community profile analyses showed no enrichment of typical model Fe(III)-reducing bacteria, such as Shewanella or Geobacter sp., but an enrichment of fermenters (e.g., Enterobacteria) during pure ferrihydrite incubations which are known to use Fe(III) as an electron sink. Instead, OM–mineral complexes favored the enrichment of microbes including Desulfobacteria and Pelosinus sp., both of which can utilize lactate and acetate as an electron donor under Fe(III)-reducing conditions. In summary, this study shows that increasing concentrations of OM in OM–mineral complexes determines microbial Fe(III) reduction rates and shapes the microbial community structure involved in the reductive dissolution of ferrihydrite. Similarities observed between the complex Fe(III)-reducing microbial consortia and the model Fe(III)-reducer S. oneidensis MR-1 suggest electron-shuttling mechanisms dominate in OM-rich environments, including soils, sediments, and fens, where natural OM interacts with Fe(III) oxides during mineral formation.

scholarly journals Flavin Electron Shuttles Dominate Extracellular Electron Transfer by Shewanella oneidensis

mBio ◽  
2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Nicholas J. Kotloski ◽  
Jeffrey A. Gralnick
Keyword(s):  
Electron Transfer ◽  
Direct Electron Transfer ◽  
Shewanella Oneidensis ◽  
Phenotypic Characterization ◽  
Extracellular Electron Transfer ◽  
Wild Type ◽  
Content Type ◽  
Electron Shuttling ◽  
Electron Shuttles ◽  
Set Up

ABSTRACT Shewanella oneidensis strain MR-1 is widely studied for its ability to respire a diverse array of soluble and insoluble electron acceptors. The ability to breathe insoluble substrates is defined as extracellular electron transfer and can occur via direct contact or by electron shuttling in S. oneidensis. To determine the contribution of flavin electron shuttles in extracellular electron transfer, a transposon mutagenesis screen was performed with S. oneidensis to identify mutants unable to secrete flavins. A multidrug and toxin efflux transporter encoded by SO_0702 was identified and renamed bfe (bacterial flavin adenine dinucleotide [FAD] exporter) based on phenotypic characterization. Deletion of bfe resulted in a severe decrease in extracellular flavins, while overexpression of bfe increased the concentration of extracellular flavins. Strains lacking bfe had no defect in reduction of soluble Fe(III), but these strains were deficient in the rate of insoluble Fe(III) oxide reduction, which was alleviated by the addition of exogenous flavins. To test a different insoluble electron acceptor, graphite electrode bioreactors were set up to measure current produced by wild-type S. oneidensis and the Δbfe mutant. With the same concentration of supplemented flavins, the two strains produced similar amounts of current. However, when exogenous flavins were not supplemented to bioreactors, bfe mutant strains produced significantly less current than the wild type. We have demonstrated that flavin electron shuttling accounts for ~75% of extracellular electron transfer to insoluble substrates by S. oneidensis and have identified the first FAD transporter in bacteria. IMPORTANCE Extracellular electron transfer by microbes is critical for the geochemical cycling of metals, bioremediation, and biocatalysis using electrodes. A controversy in the field was addressed by demonstrating that flavin electron shuttling, not direct electron transfer or nanowires, is the primary mechanism of extracellular electron transfer employed by the bacterium Shewanella oneidensis. We have identified a flavin adenine dinucleotide transporter conserved in all sequenced Shewanella species that facilitates export of flavin electron shuttles in S. oneidensis. Analysis of a strain that is unable to secrete flavins demonstrated that electron shuttling accounts for ~75% of the insoluble extracellular electron transfer capacity in S. oneidensis.

scholarly journals Tailored extracellular electron transfer pathways enhance the electroactivity of Escherichia coli

2021 ◽  
Author(s):  
Mohammed Mouhib ◽  
Melania Reggente ◽  
Lin Li ◽  
Nils Schuergers ◽  
Ardemis Anoush Boghossian
Keyword(s):  
Escherichia Coli ◽  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Electrical Current ◽  
Extracellular Electron Transfer ◽  
Organic Substrates ◽  
Transfer Rates ◽  
Electron Shuttling ◽  
E Coli ◽  
Electron Transfer Pathways

Extracellular electron transfer (EET) engineering in Escherichia coli holds great potential for bioremediation, energy and electrosynthesis applications fueled by readily available organic substrates. Due to its vast metabolic capabilities and availability of synthetic biology tools to adapt strains to specific applications, E. coli is of advantage over native exoelectrogens, but limited in electron transfer rates. We enhanced EET in engineered strains through systematic expression of electron transfer pathways differing in cytochrome composition, localization and origin. While a hybrid pathway harboring components of an E. coli nitrate reductase and the Mtr complex from the exoelectrogen Shewanella oneidensis MR-1 enhanced EET, the highest efficiency was achieved by implementing the complete Mtr pathway from S. oneidensis MR1 in E. coli. We show periplasmic electron shuttling through overexpression of a small tetraheme cytochrome to be central to the electroactivity of this strain, leading to enhanced degradation of the pollutant methyl orange and significantly increased electrical current to graphite electrodes.

scholarly journals Shewanella oneidensis MR-1 Uses Overlapping Pathways for Iron Reduction at a Distance and by Direct Contact under Conditions Relevant for Biofilms

2005 ◽  
Vol 71 (8) ◽  
pp. 4414-4426 ◽  
Author(s):  
Douglas P. Lies ◽  
Maria E. Hernandez ◽  
Andreas Kappler ◽  
Randall E. Mielke ◽  
Jeffrey A. Gralnick ◽  
...  
Keyword(s):  
Direct Contact ◽  
Iron Reduction ◽  
Shewanella Oneidensis ◽  
Live Cells ◽  
Wild Type ◽  
Electron Shuttling ◽  
Electron Shuttles ◽  
Diffusion Limited ◽  
Culture Supernatants ◽  
Maximal Reduction

ABSTRACT We developed a new method to measure iron reduction at a distance based on depositing Fe(III) (hydr)oxide within nanoporous glass beads. In this “Fe-bead” system, Shewanella oneidensis reduces at least 86.5% of the iron in the absence of direct contact. Biofilm formation accompanies Fe-bead reduction and is observable both macro- and microscopically. Fe-bead reduction is catalyzed by live cells adapted to anaerobic conditions, and maximal reduction rates require sustained protein synthesis. The amount of reactive ferric iron in the Fe-bead system is available in excess such that the rate of Fe-bead reduction is directly proportional to cell density; i.e., it is diffusion limited. Addition of either lysates prepared from anaerobic cells or exogenous electron shuttles stimulates Fe-bead reduction by S. oneidensis, but iron chelators or additional Fe(II) do not. Neither dissolved Fe(III) nor electron shuttling activity was detected in culture supernatants, implying that the mediator is retained within the biofilm matrix. Strains with mutations in omcB or mtrB show about 50% of the wild-type levels of reduction, while a cymA mutant shows less than 20% of the wild-type levels of reduction and a menF mutant shows insignificant reduction. The Fe-bead reduction defect of the menF mutant can be restored by addition of menaquinone, but menaquinone itself cannot stimulate Fe-bead reduction. Because the menF gene encodes the first committed step of menaquinone biosynthesis, no intermediates of the menaquinone biosynthetic pathway are used as diffusible mediators by this organism to promote iron reduction at a distance. CymA and menaquinone are required for both direct and indirect mineral reduction, whereas MtrB and OmcB contribute to but are not absolutely required for iron reduction at a distance.

Exemplar Abstract for Shewanella oneidensis Venkateswaran et al. 1999.

2003 ◽  
Author(s):  
Charles Thomas Parker ◽  
Dorothea Taylor ◽  
George M Garrity
Keyword(s):  
Shewanella Oneidensis

A ROLE OF PROTEINS OF THE OUTER MEMBRANE OF Shewanella oneidensis MR-1 BACTERIA IN FORMATION AND STABILIZATION OF SILVER SULFIDE NANOPARTICLES

2015 ◽  
pp. 41-48 ◽  
Author(s):  
T. A. Voeikova ◽  
A. S. Shebanova ◽  
Yu. D. Ivanov ◽  
A. L. Kaysheva ◽  
L. M. Novikova ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Shewanella Oneidensis ◽  
Silver Sulfide ◽  
Silver Sulfide Nanoparticles
Sign in / Sign up

Export Citation Format

Share Document