Microbial fuel cells （MFCs） rely on microbial conversion of organic substrates to electricity. The optimal perfor- mance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually t...Microbial fuel cells （MFCs） rely on microbial conversion of organic substrates to electricity. The optimal perfor- mance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this micro- bial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were eval- uated for three inocula including domestic wastewater （DW）, lake sediment （LS） and biogas sludge （BS） with varying substrate loading （Lsub） and external resistance （Rext） on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The IS inoculated MFCs showed highest abundance （18% ± 1%） of G. sulfurreducens, maximum current density [Imax = （690 ± 30） mA.m 2] and coulombic efficiency （CE = 29% ±1%） with acetate as the substrate./max and CE increased to （1780 ± 30） mA.m-2 and 58%± 1%, respectively, after decreasing the Rext from 1000 Ωto 200 Ω, which also correlated to a higher abundance ofG. sulfurreducens （21% ±0.7%） on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to Lsub and Roy, for of timizing electricity eneration in MFCs.展开更多
Microbes can cause or accelerate metal corrosion,leading to huge losses in corrosion damages each year.Geobacter sulfurreducens is a representative electroactive bacterium in many soils,sediments,and wastew-ater syste...Microbes can cause or accelerate metal corrosion,leading to huge losses in corrosion damages each year.Geobacter sulfurreducens is a representative electroactive bacterium in many soils,sediments,and wastew-ater systems.It has been confirmed to directly extract electrons from elemental metals.However,little is known about the effect of electron shuttles in G.sulfurreducens corrosion on stainless steel.In this study,we report that exogenous flavins promote iron-to-microbe electron transfer,accelerating micro-bial corrosion.G.sulfurreducens caused 1.3 times deeper pits and increased electron uptake(with 2 times increase of i_(corr))from stainless steel when riboflavin was added to the culture medium.OmcS-deficient mutant data suggest that G.sulfurreducens utilizes riboflavin as a bound-cofactor in outer membrane c-type cytochromes.The finding that,in the presence of microbes,riboflavin can substantially accelerate corrosion highlights the role of flavin redox cycling for enhanced iron-to-microbe electron transfer by G.sulfurreducens and provides new insights in microbial corrosion.展开更多
Microbially mediated bioreduction of iron oxyhydroxide plays an important role in the biogeochemical cycle of iron.Geobacter sulfurreducens is a representative dissimilatory ironreducing bacterium that assembles elect...Microbially mediated bioreduction of iron oxyhydroxide plays an important role in the biogeochemical cycle of iron.Geobacter sulfurreducens is a representative dissimilatory ironreducing bacterium that assembles electrically conductive pili and cytochromes.The impact of supplementation withγ-Fe_2O_3 nanoparticles(NPs)(0.2 and 0.6 g)on the G.sulfurreducens-mediated reduction of ferrihydrite was investigated.In the overall performance of microbial ferrihydrite reduction mediated byγ-Fe_2O_3 NPs,stronger reduction was observed in the presence of direct contact withγ-Fe_2O_3 NPs than with indirect contact.Compared to the production of Fe(Ⅱ)derived from biotic modification with ferrihydrite alone,increases greater than 1.6-and 1.4-fold in the production of Fe(Ⅱ)were detected in the biotic modifications in which direct contact with 0.2 g and 0.6 gγ-Fe_2O_3 NPs,respectively,occurred.X-ray diffraction analysis indicated that magnetite was a unique representative iron mineral in ferrihydrite when active G.sulfurreducens cells were in direct contact withγ-Fe_2O_3 NPs.Because of the sorption of biogenic Fe(Ⅱ)ontoγ-Fe_2O_3 NPs instead of ferrihydrite,the addition ofγ-Fe_2O_3 NPs could also contribute to increased duration of ferrihydrite reduction by preventing ferrihydrite surface passivation.Additionally,electron microscopy analysis confirmed that the direct addition ofγ-Fe_2O_3 NPs stimulated the electrically conductive pili and cytochromes to stretch,facilitating long-range electron transfer between the cells and ferrihydrite.The obtained findings provide a more comprehensive understanding of the effects of iron oxide NPs on soil biogeochemistry.展开更多
Modification of electrode surface with carboxylic acid terminated alkanethiol self-assembled monolayers （SAMs） has been found to be an effective approach to improve the extracellular electron transfer （EET） of ele...Modification of electrode surface with carboxylic acid terminated alkanethiol self-assembled monolayers （SAMs） has been found to be an effective approach to improve the extracellular electron transfer （EET） of electrochemically active bacteria （EAB） on electrode surface, but the underlying mechanism behind such enhanced EET remains unclear. In this work, the gold electrodes modified by mercapto-acetic acid and mercapto- ethylamine （Au-COOH, Au-NH2） were used as anodes in microbial electrolysis cells （MECs） inoculated with Geobacter sulfurreducens DL- 1, and their electrochemical performance and the bacteria-electrode interactions were investigated. Results showed that the Fe（CN）6^3-/4^- redox reaction occurred on the Au-NH2 with a higher rate and a lower resistance than that on the Au or the Au-COOH. Both the MECs with the Au-COOH and Au-NH2 anodes exhibited a higher current density than that with a bare Au anode. The biofilm formed on the Au-COOH was denser than that on bare Au, while the biofilm on the Au-NH2 had a greater thickness, suggesting a critical role of direct EET in this system. This work suggests that functional groups such as --COOH and-NH2 could promote electrode performance by accelerating the direct EET of EAB on electrode surface.展开更多
In this study,an Escherichia coli(E.coli)whole-cell biosensor for the specific detection of bioavailable arsenic was developed by placing a green fluorescent protein(GFP)reporter gene under the control of the ArsR1(GS...In this study,an Escherichia coli(E.coli)whole-cell biosensor for the specific detection of bioavailable arsenic was developed by placing a green fluorescent protein(GFP)reporter gene under the control of the ArsR1(GSU2952)regulatory circuit from Geobacter sulfurreducens.E.coli cells only emitted green fluorescence in the presence of arsenite and were more sensitive to arsenite when they were grown in M9 supplemented medium compared to LB medium.Under optimal test conditions,the Geobacter arsR1 promoter had a detection limit of 0.01 mM arsenite and the GFP expression was linear within a range of 0.03-0.1 mM(2.25-7.5 mg/l).These values were well below World Health Organization’s drinking water quality standard,which is 10 mg/l.The feasibility of using this whole-cell biosensor to detect arsenic in water samples,such as arsenic polluted tap water and landfill leachate was verified.The biosensor was determined to be just as sensitive as atomic fluorescence spectrometry.This study examines the potential applications of biosensors constructed with Geobacter ArsR-Pars regulatory circuits and provides a rapid and cost-effective tool that can be used for arsenic detection in water samples.展开更多
Extracellular electron transfer(EET)plays a critical role in bioelectrochemical processes,allowing cou-pling between microorganisms and extracellular solid-state electrodes,metals,or other cells in energy metabolism.P...Extracellular electron transfer(EET)plays a critical role in bioelectrochemical processes,allowing cou-pling between microorganisms and extracellular solid-state electrodes,metals,or other cells in energy metabolism.Previous studies have suggested a role for outer-surface c-type cytochromes in direct metal-to-microbe electron transfer by Geobacter sulfurreducens,a model electroactive bacterium.Here,we ex-amined the possibility of other microbially produced electrical contacts by deleting the gene for PilA,the protein monomer that G.sulfurreducens assembles into electrically conductive protein nanowires(e-pili).Deleting pilA gene inhibited electron extraction from pure iron and 316L stainless steel up to 31%and 81%,respectively more than deleting the gene for the outer-surface cytochrome OmcS.This PilA-deficient phenotype,and the observation that relatively thick biofilms(21.7μm)grew on the metal surfaces at multi-cell distances from the metal surfaces suggest that e-pili contributed significantly to microbial cor-rosion via direct metal-to-microbe electron transfer.These results have implications for the fundamental understanding of electron harvest via e-pili by electroactive microbes,their uses in bioenergy production,as well as in monitoring and mitigation of metal biocorrosion.展开更多
基金grateful to Danida Fellowship Centre for supporting the research project (Biobased electricity in developing countries,DFC No.11-091 Ris?)The financial support from China Scholarship Council (CSC No.2011635051) for Guotao Sun is gratefully acknowledged.Annette E.Jensen,DTU is thanked for technical support
文摘Microbial fuel cells （MFCs） rely on microbial conversion of organic substrates to electricity. The optimal perfor- mance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this micro- bial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were eval- uated for three inocula including domestic wastewater （DW）, lake sediment （LS） and biogas sludge （BS） with varying substrate loading （Lsub） and external resistance （Rext） on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The IS inoculated MFCs showed highest abundance （18% ± 1%） of G. sulfurreducens, maximum current density [Imax = （690 ± 30） mA.m 2] and coulombic efficiency （CE = 29% ±1%） with acetate as the substrate./max and CE increased to （1780 ± 30） mA.m-2 and 58%± 1%, respectively, after decreasing the Rext from 1000 Ωto 200 Ω, which also correlated to a higher abundance ofG. sulfurreducens （21% ±0.7%） on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to Lsub and Roy, for of timizing electricity eneration in MFCs.
文摘采用新兴的代谢组学技术,筛选差异性细胞代谢物,分析甲基汞生成和调控的关键代谢通路。在典型环境污染浓度(0~100μg/L) Hg(Ⅱ)的胁迫下,汞甲基化微生物Geobacter sulfurreducens PCA吸附/吸收的Hg(Ⅱ)成为参与汞还原和甲基化的主要反应物质。初始Hg(Ⅱ)浓度为10μg/L时, G. sulfurreducens PCA达到最高汞甲基化效率3.09%±0.16%。代谢组学数据显示,Hg(Ⅱ)胁迫对胞内的碳水化合物代谢、核苷酸代谢和氨基酸代谢造成干扰。为了应对Hg(Ⅱ)胁迫, G. sulfurreducens PCA增大了对能量的需求,用来调控汞生物甲基化反应,并对受损DNA进行修复。
基金supported by the National Natural Science Foundation of China(Nos.52101078,U2006219)the National Key Research and Development Program of China(No.2020YFA0907300)+1 种基金the Fundamental Research Funds for the Central Universities of the Ministry of Education of China(Nos.N2102009,N2002019)Liaoning Revitalization Talents Program(No.XLYC1907158).
文摘Microbes can cause or accelerate metal corrosion,leading to huge losses in corrosion damages each year.Geobacter sulfurreducens is a representative electroactive bacterium in many soils,sediments,and wastew-ater systems.It has been confirmed to directly extract electrons from elemental metals.However,little is known about the effect of electron shuttles in G.sulfurreducens corrosion on stainless steel.In this study,we report that exogenous flavins promote iron-to-microbe electron transfer,accelerating micro-bial corrosion.G.sulfurreducens caused 1.3 times deeper pits and increased electron uptake(with 2 times increase of i_(corr))from stainless steel when riboflavin was added to the culture medium.OmcS-deficient mutant data suggest that G.sulfurreducens utilizes riboflavin as a bound-cofactor in outer membrane c-type cytochromes.The finding that,in the presence of microbes,riboflavin can substantially accelerate corrosion highlights the role of flavin redox cycling for enhanced iron-to-microbe electron transfer by G.sulfurreducens and provides new insights in microbial corrosion.
基金supported by the National Natural Science Foundation of China (Nos. 41571449, 41271260, 41276101 and 41807035)the Fundamental Research Fund for the Central Universities of China (No. 20720160083)+2 种基金the Natural Science Foundation of Fujian Province of China (Nos. 2018J05073 and 2018Y0074)the Project of Educational Scientific Research of Fujian Province of China (Nos. JAT170831 and JA13344)the Open Fund of Key Laboratory of Measurement and Control System for Coastal Environment of China (No. S1-KF1701)
文摘Microbially mediated bioreduction of iron oxyhydroxide plays an important role in the biogeochemical cycle of iron.Geobacter sulfurreducens is a representative dissimilatory ironreducing bacterium that assembles electrically conductive pili and cytochromes.The impact of supplementation withγ-Fe_2O_3 nanoparticles(NPs)(0.2 and 0.6 g)on the G.sulfurreducens-mediated reduction of ferrihydrite was investigated.In the overall performance of microbial ferrihydrite reduction mediated byγ-Fe_2O_3 NPs,stronger reduction was observed in the presence of direct contact withγ-Fe_2O_3 NPs than with indirect contact.Compared to the production of Fe(Ⅱ)derived from biotic modification with ferrihydrite alone,increases greater than 1.6-and 1.4-fold in the production of Fe(Ⅱ)were detected in the biotic modifications in which direct contact with 0.2 g and 0.6 gγ-Fe_2O_3 NPs,respectively,occurred.X-ray diffraction analysis indicated that magnetite was a unique representative iron mineral in ferrihydrite when active G.sulfurreducens cells were in direct contact withγ-Fe_2O_3 NPs.Because of the sorption of biogenic Fe(Ⅱ)ontoγ-Fe_2O_3 NPs instead of ferrihydrite,the addition ofγ-Fe_2O_3 NPs could also contribute to increased duration of ferrihydrite reduction by preventing ferrihydrite surface passivation.Additionally,electron microscopy analysis confirmed that the direct addition ofγ-Fe_2O_3 NPs stimulated the electrically conductive pili and cytochromes to stretch,facilitating long-range electron transfer between the cells and ferrihydrite.The obtained findings provide a more comprehensive understanding of the effects of iron oxide NPs on soil biogeochemistry.
基金The authors wish to thank the National Natural Science Foundation of China （Grant No. 21477120）, the Program for Changjiang Scholars and Innovative Research Team in University and the Collaborative Innovation Center of Suzhou Nano Science and Technology of Ministry of Education of China for the partial support of this work.
文摘Modification of electrode surface with carboxylic acid terminated alkanethiol self-assembled monolayers （SAMs） has been found to be an effective approach to improve the extracellular electron transfer （EET） of electrochemically active bacteria （EAB） on electrode surface, but the underlying mechanism behind such enhanced EET remains unclear. In this work, the gold electrodes modified by mercapto-acetic acid and mercapto- ethylamine （Au-COOH, Au-NH2） were used as anodes in microbial electrolysis cells （MECs） inoculated with Geobacter sulfurreducens DL- 1, and their electrochemical performance and the bacteria-electrode interactions were investigated. Results showed that the Fe（CN）6^3-/4^- redox reaction occurred on the Au-NH2 with a higher rate and a lower resistance than that on the Au or the Au-COOH. Both the MECs with the Au-COOH and Au-NH2 anodes exhibited a higher current density than that with a bare Au anode. The biofilm formed on the Au-COOH was denser than that on bare Au, while the biofilm on the Au-NH2 had a greater thickness, suggesting a critical role of direct EET in this system. This work suggests that functional groups such as --COOH and-NH2 could promote electrode performance by accelerating the direct EET of EAB on electrode surface.
基金supported by the Fundamental Research Funds for the Central Universities[grant numbers BLX201934,2019ZY19]Beijing Municipal Education Commission through Innovative Transdisciplinary Program“Ecological Restoration Engineering”.
文摘In this study,an Escherichia coli(E.coli)whole-cell biosensor for the specific detection of bioavailable arsenic was developed by placing a green fluorescent protein(GFP)reporter gene under the control of the ArsR1(GSU2952)regulatory circuit from Geobacter sulfurreducens.E.coli cells only emitted green fluorescence in the presence of arsenite and were more sensitive to arsenite when they were grown in M9 supplemented medium compared to LB medium.Under optimal test conditions,the Geobacter arsR1 promoter had a detection limit of 0.01 mM arsenite and the GFP expression was linear within a range of 0.03-0.1 mM(2.25-7.5 mg/l).These values were well below World Health Organization’s drinking water quality standard,which is 10 mg/l.The feasibility of using this whole-cell biosensor to detect arsenic in water samples,such as arsenic polluted tap water and landfill leachate was verified.The biosensor was determined to be just as sensitive as atomic fluorescence spectrometry.This study examines the potential applications of biosensors constructed with Geobacter ArsR-Pars regulatory circuits and provides a rapid and cost-effective tool that can be used for arsenic detection in water samples.
基金supported by the National Natu-ral Science Foundation of China(Nos.U2006219 and 52101078)China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202120)+2 种基金the National Key Research and Development Pro-gram of China(No.2020YFA0907300)the Fundamental Research Funds for the Central Universities of the Ministry of Education of China(Nos.N2102009 and N2002019)the Liaoning Revitaliza-tion Talents Program(No.XLYC1907158).
文摘Extracellular electron transfer(EET)plays a critical role in bioelectrochemical processes,allowing cou-pling between microorganisms and extracellular solid-state electrodes,metals,or other cells in energy metabolism.Previous studies have suggested a role for outer-surface c-type cytochromes in direct metal-to-microbe electron transfer by Geobacter sulfurreducens,a model electroactive bacterium.Here,we ex-amined the possibility of other microbially produced electrical contacts by deleting the gene for PilA,the protein monomer that G.sulfurreducens assembles into electrically conductive protein nanowires(e-pili).Deleting pilA gene inhibited electron extraction from pure iron and 316L stainless steel up to 31%and 81%,respectively more than deleting the gene for the outer-surface cytochrome OmcS.This PilA-deficient phenotype,and the observation that relatively thick biofilms(21.7μm)grew on the metal surfaces at multi-cell distances from the metal surfaces suggest that e-pili contributed significantly to microbial cor-rosion via direct metal-to-microbe electron transfer.These results have implications for the fundamental understanding of electron harvest via e-pili by electroactive microbes,their uses in bioenergy production,as well as in monitoring and mitigation of metal biocorrosion.
