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Rodríguez-Torres LM, Huerta-Miranda GA, Martínez-García AL, Mazón-Montijo DA, Hernández-Eligio A, Miranda-Hernández M, Juárez K. Influence of support materials on the electroactive behavior, structure and gene expression of wild type and GSU1771-deficient mutant of Geobacter sulfurreducens biofilms. Environ Sci Pollut Res Int 2024:10.1007/s11356-024-33612-3. [PMID: 38758442 DOI: 10.1007/s11356-024-33612-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 05/05/2024] [Indexed: 05/18/2024]
Abstract
Geobacter sulfurreducens DL1 is a metal-reducing dissimilatory bacterium frequently used to produce electricity in bioelectrochemical systems (BES). The biofilm formed on electrodes is one of the most important factors for efficient electron transfer; this is possible due to the production of type IV pili and c-type cytochromes that allow it to carry out extracellular electron transfer (EET) to final acceptors. In this study, we analyzed the biofilm formed on different support materials (glass, hematite (Fe2O3) on glass, fluorine-doped tin oxide (FTO) semiconductor glass, Fe2O3 on FTO, graphite, and stainless steel) by G. sulfurreducens DL1 (WT) and GSU1771-deficient strain mutant (Δgsu1771). GSU1771 is a transcriptional regulator that controls the expression of several genes involved in electron transfer. Different approaches and experimental tests were carried out with the biofilms grown on the different support materials including structure analysis by confocal laser scanning microscopy (CLSM), characterization of electrochemical activity, and quantification of relative gene expression by RT-qPCR. The gene expression of selected genes involved in EET was analyzed, observing an overexpression of pgcA, omcS, omcM, and omcF from Δgsu1771 biofilms compared to those from WT, also the overexpression of the epsH gene, which is involved in exopolysaccharide synthesis. Although we observed that for the Δgsu1771 mutant strain, the associated redox processes are similar to the WT strain, and more current is produced, we think that this could be associated with a higher relative expression of certain genes involved in EET and in the production of exopolysaccharides despite the chemical environment where the biofilm develops. This study supports that G. sulfurreducens is capable of adapting to the electrochemical environment where it grows.
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Affiliation(s)
- Luis Miguel Rodríguez-Torres
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001. Col. Chamilpa, 62210, Cuernavaca, Morelos, México
| | - Guillermo Antonio Huerta-Miranda
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001. Col. Chamilpa, 62210, Cuernavaca, Morelos, México
| | - Ana Luisa Martínez-García
- Centro de Investigación en Materiales Avanzados S. C., Subsede Monterrey, Grupo de Investigación DORA-Lab, 66628, Apodaca, N. L, México
- Centro de Investigación e Innovación Tecnológica (CIIT), Grupo de Investigación DORA-Lab, Tecnológico Nacional de México Campus Nuevo León (TECNL), 66629, Apodaca, N. L, México
| | - Dalia Alejandra Mazón-Montijo
- Centro de Investigación en Materiales Avanzados S. C., Subsede Monterrey, Grupo de Investigación DORA-Lab, 66628, Apodaca, N. L, México
- Centro de Investigación e Innovación Tecnológica (CIIT), Grupo de Investigación DORA-Lab, Tecnológico Nacional de México Campus Nuevo León (TECNL), 66629, Apodaca, N. L, México
- Investigadores Por México, CONAHCYT, Ciudad de México, México
| | - Alberto Hernández-Eligio
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001. Col. Chamilpa, 62210, Cuernavaca, Morelos, México
- Investigadores Por México, CONAHCYT, Ciudad de México, México
| | - Margarita Miranda-Hernández
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Priv. Xochicalco, 62580, Temixco, Morelos, México
| | - Katy Juárez
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001. Col. Chamilpa, 62210, Cuernavaca, Morelos, México.
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Yunda E, Phan Le QN, Björn E, Ramstedt M. Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate. Biofilm 2023; 6:100144. [PMID: 37583615 PMCID: PMC10424081 DOI: 10.1016/j.bioflm.2023.100144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/03/2023] [Accepted: 07/24/2023] [Indexed: 08/17/2023] Open
Abstract
Geobacter species are common in iron-rich environments and can contribute to formation of methylmercury (MeHg), a neurotoxic compound with high bioaccumulation potential formed as a result of bacterial and archaeal physiological activity. Geobacter sulfurreducens can utilize various electron acceptors for growth including iron hydroxides or fumarate. However, it remains poorly understood how the growth on these compounds affects physiological properties of bacterial cells in biofilms, including the capacity to produce MeHg. The purpose of this study was to determine changes in the biochemical composition of G. sulfurreducens during biofilm cultivation in media containing iron hydroxide or fumarate, and to quantify mercury (Hg) methylation capacity of the formed biofilms. Biofilms were characterized by Fourier-transform infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR), Resonance Raman spectroscopy and confocal laser scanning microscopy. MeHg formation was quantified by mass spectrometry after incubation of biofilms with 100 nM Hg. The results of ATR-FTIR experiments showed that in presence of fumarate, G. sulfurreducens biofilm formation was accompanied by variation in content of the energy-reserve polymer glycogen over time, which could be cancelled by the addition of supplementary nutrients (yeast extract). In contrast, biofilms cultivated on Fe(III) hydroxide did not accumulate glycogen. The ATR-FTIR results further suggested that Fe(III) hydroxide surfaces bind cells via phosphate and carboxylate groups of bacteria that form complexes with iron. Furthermore, biofilms grown on Fe(III) hydroxide had higher fraction of oxidized cytochromes and produced two to three times less biomass compared to conditions with fumarate. Normalized to biofilm volume, the content of MeHg was similar in assays with biofilms grown on Fe(III) hydroxide and on fumarate (with yeast extract and without). These results suggest that G. sulfurreducens biofilms produce MeHg irrespectively from glycogen content and cytochrome redox state in the cells, and warrant further investigation of the mechanisms controlling this process.
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Affiliation(s)
- Elena Yunda
- Department of Chemistry, Umeå University, Sweden
| | | | - Erik Björn
- Department of Chemistry, Umeå University, Sweden
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Jaramillo-Rodríguez JB, Vega-Alvarado L, Rodríguez-Torres LM, Huerta-Miranda GA, Hernández-Eligio A, Juarez K. Global transcriptional analysis of Geobacter sulfurreducens gsu1771 mutant biofilm grown on two different support structures. PLoS One 2023; 18:e0293359. [PMID: 37878651 PMCID: PMC10599522 DOI: 10.1371/journal.pone.0293359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 09/28/2023] [Indexed: 10/27/2023] Open
Abstract
Electroactive biofilms formation by the metal-reducing bacterium Geobacter sulfurreducens is a step crucial for bioelectricity generation and bioremediation. The transcriptional regulator GSU1771 controls the expression of essential genes involved in electron transfer and biofilm formation in G. sulfurreducens, with GSU1771-deficient producing thicker and more electroactive biofilms. Here, RNA-seq analyses were conducted to compare the global gene expression patterns of wild-type and Δgsu1771 mutant biofilms grown on non-conductive (glass) and conductive (graphite electrode) materials. The Δgsu1771 biofilm grown on the glass surface exhibited 467 differentially expressed (DE) genes (167 upregulated and 300 downregulated) versus the wild-type biofilm. In contrast, the Δgsu1771 biofilm grown on the graphite electrode exhibited 119 DE genes (79 upregulated and 40 downregulated) versus the wild-type biofilm. Among these DE genes, 67 were also differentially expressed in the Δgsu1771 biofilm grown on glass (56 with the same regulation and 11 exhibiting counter-regulation). Among the upregulated genes in the Δgsu1771 biofilms, we identified potential target genes involved in exopolysaccharide synthesis (gsu1961-63, gsu1959, gsu1972-73, gsu1976-77). RT-qPCR analyses were then conducted to confirm the differential expression of a selection of genes of interest. DNA-protein binding assays demonstrated the direct binding of the GSU1771 regulator to the promoter region of pgcA, pulF, relA, and gsu3356. Furthermore, heme-staining and western blotting revealed an increase in c-type cytochromes including OmcS and OmcZ in Δgsu1771 biofilms. Collectively, our findings demonstrated that GSU1771 is a global regulator that controls extracellular electron transfer and exopolysaccharide synthesis in G. sulfurreducens, which is crucial for electroconductive biofilm development.
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Affiliation(s)
- Juan B. Jaramillo-Rodríguez
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Leticia Vega-Alvarado
- Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, México
| | - Luis M. Rodríguez-Torres
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Guillermo A. Huerta-Miranda
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Alberto Hernández-Eligio
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- Investigador por México, Consejo Nacional de Ciencia y Tecnología, Ciudad de México, México
| | - Katy Juarez
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
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Chen C, Zhang Z, Xu P, Hu H, Tang H. Anaerobic biodegradation of polycyclic aromatic hydrocarbons. Environ Res 2023; 223:115472. [PMID: 36773640 DOI: 10.1016/j.envres.2023.115472] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/25/2023] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
Although many anaerobic microorganisms that can degrade PAHs have been harnessed, there is still a large gap between laboratory achievements and practical applications. Here, we review the recent advances in the biodegradation of PAHs under anoxic conditions and highlight the mechanistic insights into the metabolic pathways and functional genes. Achievements of practical application and enhancing strategies of anaerobic PAHs bioremediation in soil were summarized. Based on the concerned issues during research, perspectives of further development were proposed including time-consuming enrichment, byproducts with unknown toxicity, and activity inhibition with low temperatures. In addition, meta-omics, synthetic biology and engineering microbiome of developing microbial inoculum for anaerobic bioremediation applications are discussed. We anticipate that integrating the theoretical research on PAHs anaerobic biodegradation and its successful application will advance the development of anaerobic bioremediation.
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Affiliation(s)
- Chao Chen
- College of Life Science, Dalian Minzu University, Dalian, 116600, Liaoning, China; State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhan Zhang
- China Tobacco Henan Industrial Co. Ltd., Zhengzhou, 450000, China
| | - Ping Xu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Haiyang Hu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
| | - Hongzhi Tang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
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5
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Karavaeva V, Sousa FL. Modular structure of complex II: An evolutionary perspective. Biochim Biophys Acta Bioenerg 2023; 1864:148916. [PMID: 36084748 DOI: 10.1016/j.bbabio.2022.148916] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 07/21/2022] [Accepted: 09/02/2022] [Indexed: 11/25/2022]
Abstract
Succinate dehydrogenases (SDHs) and fumarate reductases (FRDs) catalyse the interconversion of succinate and fumarate, a reaction highly conserved in all domains of life. The current classification of SDH/FRDs is based on the structure of the membrane anchor subunits and their cofactors. It is, however, unknown whether this classification would hold in the context of evolution. In this work, a large-scale comparative genomic analysis of complex II addresses the questions of its taxonomic distribution and phylogeny. Our findings report that for types C, D, and F, structural classification and phylogeny go hand in hand, while for types A, B and E the situation is more complex, highlighting the possibility for their classification into subgroups. Based on these findings, we proposed a revised version of the evolutionary scenario for these enzymes in which a primordial soluble module, corresponding to the cytoplasmatic subunits, would give rise to the current diversity via several independent membrane anchor attachment events.
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Affiliation(s)
- Val Karavaeva
- Department of Functional and Evolutionary Ecology, University of Vienna, Djerassiplatz 1, 1030 Wien, Austria
| | - Filipa L Sousa
- Department of Functional and Evolutionary Ecology, University of Vienna, Djerassiplatz 1, 1030 Wien, Austria.
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Frühauf‐Wyllie HM, Holtmann D. Geobacter sulfurreducens
metabolism at different donor/acceptor ratios. Microbiologyopen 2022; 11:e1322. [PMID: 36314758 PMCID: PMC9494351 DOI: 10.1002/mbo3.1322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 11/11/2022] Open
Abstract
Geobacter species have great application potential in remediation processes and electrobiotechnology. In all applications, understanding the metabolism will enable target‐oriented optimization of the processes. The typical electron donor and carbon source of the Geobacter species is acetate, while fumarate is the usual electron acceptor. Here, we could show that depending on the donor/acceptor ratio in batch cultivation of Geobacter sulfurreducens different product patterns occur. With a donor/acceptor ratio of 1:2.5 malate accumulated as an intermediate product but was metabolized to succinate subsequently. At the end of the cultivation, the ratio of fumarate consumed and succinate produced was approximately 1:1. When fumarate was added in excess, malate accumulated in the fermentation broth without further metabolization. After the addition of acetate to stationary cells, malate concentration decreased immediately and additional succinate was synthesized. Finally, it was shown that also resting cells of G. sulfurreducens could efficiently convert fumarate to malate without an additional electron donor. Overall, it was demonstrated that by altering the donor/acceptor ratio, targeted optimization of the metabolite conversion by G. sulfurreducens can be realized.
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Affiliation(s)
- Hanna Marianne Frühauf‐Wyllie
- Department of Chemical Technology DECHEMA Forschungsinstitut Frankfurt am Main Germany
- Technische Hochschule Mittelhessen, Institut für Bioverfahrenstechnik und Pharmazeutische Technologie Gießen Germany
| | - Dirk Holtmann
- Technische Hochschule Mittelhessen, Institut für Bioverfahrenstechnik und Pharmazeutische Technologie Gießen Germany
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Shi XC, Tremblay PL, Xue M, Song X, Zhang T. Fumarate disproportionation by Geobacter sulfurreducens and its involvement in biocorrosion and interspecies electron transfer. Sci Total Environ 2022; 827:154251. [PMID: 35245554 DOI: 10.1016/j.scitotenv.2022.154251] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 02/14/2022] [Accepted: 02/26/2022] [Indexed: 06/14/2023]
Abstract
The model electroactive bacterium Geobacter sulfurreducens can acquire electrons directly from solid donors including metals and other species. Reports on this physiology concluding that solid donors are the only electron sources were conducted with fumarate believed to serve exclusively as the terminal electron acceptor (TEA). Here, G. sulfurreducens was repeatedly transferred for adaptation within a growth medium containing only fumarate and no other solid or soluble substrate. The resulting evolved strain grew efficiently with either the C4-dicarboxylate fumarate or malate acting simultaneously as electron donor, carbon source, and electron acceptor via disproportionation. Whole-genome sequencing identified 38 mutations including one in the regulator PilR known to repress the expression of the C4-dicarboxylate antiporter DcuB essential to G. sulfurreducens when growing with fumarate. Futhermore, the PilR mutation was identical to the sole mutation previously reported in an evolved G. sulfurreducens grown in a co-culture assumed to derive energy solely from direct interspecies electron transfer, but cultivated with fumarate as the TEA. When cultivating the fumarate-adapted strain in the presence of stainless steel and fumarate, biocorrosion was observed and bacterial growth was accelerated 2.3 times. These results suggest that G. sulfurreducens can conserve energy concomitantly from C4-dicarboxylate disproportionation and the oxidation of a solid electron donor. This co-metabolic capacity confers an advantage to Geobacter for survival and colonization and explains in part why these microbes are omnipresent in different anaerobic ecosystems.
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Affiliation(s)
- Xiao-Chen Shi
- School of Chemistry, Chemical Engineering, and Life Science, Wuhan University of Technology, Wuhan 430070, PR China; School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, PR China; Wuhan University of Technology Advanced Engineering Technology Research Institute of Zhongshan City, Zhongshan 528437, PR China
| | - Pier-Luc Tremblay
- School of Chemistry, Chemical Engineering, and Life Science, Wuhan University of Technology, Wuhan 430070, PR China; State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, PR China; Sanya Science and Education Innovation Park, Wuhan University of Technology, Sanya 572024, PR China
| | - Miao Xue
- Institut WUT-AMU, Wuhan University of Technology, Wuhan 430070, PR China
| | - Xinyi Song
- Institut WUT-AMU, Wuhan University of Technology, Wuhan 430070, PR China
| | - Tian Zhang
- School of Chemistry, Chemical Engineering, and Life Science, Wuhan University of Technology, Wuhan 430070, PR China; School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, PR China; Institut WUT-AMU, Wuhan University of Technology, Wuhan 430070, PR China; State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, PR China; Sanya Science and Education Innovation Park, Wuhan University of Technology, Sanya 572024, PR China.
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Karamash M, Stumpe M, Dengjel J, Salgueiro CA, Giese B, Fromm KM. Reduction Kinetic of Water Soluble Metal Salts by Geobacter sulfurreducens: Fe2+/Hemes Stabilize and Regulate Electron Flux Rates. Front Microbiol 2022; 13:909109. [PMID: 35783399 PMCID: PMC9248073 DOI: 10.3389/fmicb.2022.909109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/20/2022] [Indexed: 01/17/2023] Open
Abstract
Geobacter sulfurreducens is a widely applied microorganism for the reduction of toxic metal salts, as an electron source for bioelectrochemical devices, and as a reagent for the synthesis of nanoparticles. In order to understand the influence of metal salts, and of electron transporting, multiheme c-cytochromes on the electron flux during respiration of G. sulfurreducens, the reduction kinetic of Fe3+, Co3+, V5+, Cr6+, and Mn7+ containing complexes were measured. Starting from the resting phase, each G. sulfurreducens cell produced an electron flux of 3.7 × 105 electrons per second during the respiration process. Reduction rates were within ± 30% the same for the 6 different metal salts, and reaction kinetics were of zero order. Decrease of c-cytochrome concentrations by downregulation and mutation demonstrated that c-cytochromes stabilized respiration rates by variation of their redox states. Increasing Fe2+/heme levels increased electron flux rates, and induced respiration flexibility. The kinetic effects parallel electrochemical results of G. sulfurreducens biofilms on electrodes, and might help to optimize bioelectrochemical devices.
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Affiliation(s)
- Maksym Karamash
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
| | - Michael Stumpe
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Carlos A. Salgueiro
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, School of Science and Technology, NOVA University Lisbon, Costa da Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, Chemistry Department, School of Science and Technology, NOVA University Lisbon, Costa da Caparica, Portugal
| | - Bernd Giese
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
- *Correspondence: Bernd Giese,
| | - Katharina M. Fromm
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
- Katharina M. Fromm,
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Spring S, Rohde M, Bunk B, Spröer C, Will SE, Neumann-Schaal M. New insights into the energy metabolism and taxonomy of Deferribacteres revealed by the characterization of a new isolate from a hypersaline microbial mat. Environ Microbiol 2022; 24:2543-2575. [PMID: 35415868 DOI: 10.1111/1462-2920.15999] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/04/2022] [Indexed: 12/13/2022]
Abstract
Strain L21-Ace-BEST , isolated from a lithifying cyanobacterial mat, could be assigned to a novel species and genus within the Deferribacteres. It is an important model organism for the study of anaerobic acetate degradation under hypersaline conditions. The metabolism of strain L21-Ace-BEST was characterized by biochemical studies, comparative genome analyses, and the evaluation of gene expression patterns. The central metabolic pathway is the citric acid cycle, which is mainly controlled by the enzyme succinyl-CoA:acetate-CoA transferase. The potential use of a reversed oxidative citric acid cycle to fix CO2 has been revealed through genome analysis. However, no autotrophic growth was detected in this strain, whereas sulfide and H2 can be used mixotrophically. Preferred electron acceptors for the anaerobic oxidation of acetate are nitrate, fumarate and DMSO, while oxygen can be utilized only under microoxic conditions. Aerotolerant growth by fermentation was observed at higher oxygen concentrations. The redox cycling of sulfur/sulfide enables the generation of reducing power for the assimilation of acetate during growth and could prevent the over-reduction of cells in stationary phase. Extracellular electron transfer appears to be an essential component of the respiratory metabolism in this clade of Deferribacteres and may be involved in the reduction of nitrite to ammonium. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Stefan Spring
- Department Microorganisms, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Manfred Rohde
- Central Facility for Microscopy, Helmholtz Centre for Infection Research, HZI, Braunschweig, Germany
| | - Boyke Bunk
- Department Bioinformatics, Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Cathrin Spröer
- Department Bioinformatics, Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Sabine Eva Will
- Research Group Metabolomics, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Meina Neumann-Schaal
- Research Group Metabolomics, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
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Hernández-Eligio A, Huerta-Miranda GA, Martínez-Bahena S, Castrejón-López D, Miranda-Hernández M, Juárez K. GSU1771 regulates extracellular electron transfer and electroactive biofilm formation in Geobacter sulfurreducens: Genetic and electrochemical characterization. Bioelectrochemistry 2022; 145:108101. [PMID: 35334296 DOI: 10.1016/j.bioelechem.2022.108101] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 03/15/2022] [Accepted: 03/16/2022] [Indexed: 11/21/2022]
Abstract
Type IV pili and the >100c-type cytochromes in Geobacter sulfurreducens are essential for extracellular electron transfer (EET) towards metal oxides and electrodes. A previous report about a mutation in the gsu1771 gene indicated an enhanced reduction of insoluble Fe(III) oxides coupled with increased pilA expression. Herein, a marker-free gsu1771-deficient mutant was constructed and characterized to assess the role of this regulator in EET and the formation of electroactive biofilms. Deleting this gene delayed microbial growth in the acetate/fumarate media (electron donor and acceptor, respectively). However, this mutant reduced soluble and insoluble Fe(III) oxides more efficiently. Heme staining, western blot, and RT-qPCR analyses demonstrated that GSU1771 regulates the transcription of several genes (including pilA) and many c-type cytochromes involved in EET, suggesting the broad regulatory role of this protein. DNA-protein binding assays indicated that GSU1771 directly regulates the transcription of pilA, omcE, omcS, and omcZ. Additionally, gsu1771-deficient mutant biofilms are thicker than wild-type strains. Electrochemical studies revealed that the current produced by this biofilm was markedly higher than the wild-type strains (approximately 100-fold). Thus, demonstrating the role of GSU1771 in the EET pathway and establishing a methodology to develop highly electroactive G. sulfurreducens mutants.
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Krige A, Ramser K, Sjöblom M, Christakopoulos P, Rova U. A New Approach for Evaluating Electron Transfer Dynamics by Using In Situ Resonance Raman Microscopy and Chronoamperometry in Conjunction with a Dynamic Model. Appl Environ Microbiol 2020; 86:e01535-20. [PMID: 32826217 DOI: 10.1128/AEM.01535-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 08/09/2020] [Indexed: 01/30/2023] Open
Abstract
Bioelectrochemical systems can fill a vast array of application niches, due to the control of redox reactions that it offers. Although native microorganisms are preferred for applications such as bioremediation, more control is required for applications such as biosensors or biocomputing. The development of a chassis organism, in which the EET is well defined and readily controllable, is therefore essential. The combined approach in this work offers a unique way of monitoring and describing the reaction kinetics of a G. sulfurreducens biofilm, as well as offering a dynamic model that can be used in conjunction with applications such as biosensors. Geobacter sulfurreducens is a good candidate as a chassis organism due to its ability to form thick, conductive biofilms, enabling long-distance extracellular electron transfer (EET). Due to the complexity of EET pathways in G. sulfurreducens, a dynamic approach is required to study genetically modified EET rates in the biofilm. By coupling online resonance Raman microscopy with chronoamperometry, we were able to observe the dynamic discharge response in the biofilm’s cytochromes to an increase in anode voltage. Measuring the heme redox state alongside the current allows for the fitting of a dynamic model using the current response and a subsequent validation of the model via the value of a reduced cytochrome c Raman peak. The modeled reduced cytochromes closely fitted the Raman response data from the G. sulfurreducens wild-type strain, showing the oxidation of heme groups in cytochromes until a new steady state was achieved. Furthermore, the use of a dynamic model also allows for the calculation of internal rates, such as acetate and NADH consumption rates. The Raman response of a mutant lacking OmcS showed a higher initial oxidation rate than predicted, followed by an almost linear decrease of the reduced mediators. The increased initial rate could be attributed to an increase in biofilm conductivity, previously observed in biofilms lacking OmcS. One explanation for this is that OmcS acts as a conduit between cytochromes; therefore, deleting the gene restricts the rate of electron transfer to the extracellular matrix. This could, however, be modeled assuming a linear oxidation rate of intercellular mediators. IMPORTANCE Bioelectrochemical systems can fill a vast array of application niches, due to the control of redox reactions that it offers. Although native microorganisms are preferred for applications such as bioremediation, more control is required for applications such as biosensors or biocomputing. The development of a chassis organism, in which the EET is well defined and readily controllable, is therefore essential. The combined approach in this work offers a unique way of monitoring and describing the reaction kinetics of a G. sulfurreducens biofilm, as well as offering a dynamic model that can be used in conjunction with applications such as biosensors.
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Zhang T, Shi XC, Ding R, Xu K, Tremblay PL. The hidden chemolithoautotrophic metabolism of Geobacter sulfurreducens uncovered by adaptation to formate. ISME J 2020; 14:2078-2089. [PMID: 32398660 DOI: 10.1038/s41396-020-0673-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 04/24/2020] [Accepted: 04/29/2020] [Indexed: 02/01/2023]
Abstract
Multiple Fe(III)-reducing Geobacter species including the model Geobacter sulfurreducens are thought to be incapable of carbon dioxide fixation. The discovery of the reversed oxidative tricarboxylic acid cycle (roTCA) for CO2 reduction with citrate synthase as key enzyme raises the possibility that G. sulfurreducens harbors the metabolic potential for chemolithoautotrophic growth. We investigate this hypothesis by transferring G. sulfurreducens PCA serially with Fe(III) as electron acceptor and formate as electron donor and carbon source. The evolved strain T17-3 grew chemolithoautotrophically with a 2.7-fold population increase over 48 h and a Fe(III) reduction rate of 417.5 μM h-1. T17-3 also grew with CO2 as carbon source. Mutations in T17-3 and enzymatic assays point to an adaptation process where the succinyl-CoA synthetase, which is inactive in the wild-type, became active to complete the roTCA cycle. Deletion of the genes coding for the succinyl-CoA synthetase in T17-3 prevented growth with formate as substrate. Enzymatic assays also showed that the citrate synthase can perform the necessary cleavage of citrate for the functional roTCA cycle. These results demonstrate that G. sulfurreducens after adaptation reduced CO2 via the roTCA cycle. This previously hidden metabolism can be harnessed for biotechnological applications and suggests hidden ecological functions for Geobacter.
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Affiliation(s)
- Tian Zhang
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, 430070, PR China. .,School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, PR China. .,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, 430070, PR China.
| | - Xiao-Chen Shi
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, 430070, PR China.,School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, 430070, PR China.,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Ran Ding
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, 430070, PR China.,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Kai Xu
- Center for Material Research and Analysis, Wuhan University of Technology, Wuhan, 430070, PR China
| | - Pier-Luc Tremblay
- State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, 430070, PR China. .,School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, 430070, PR China.
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Engel CEA, Vorländer D, Biedendieck R, Krull R, Dohnt K. Quantification of microaerobic growth of Geobacter sulfurreducens. PLoS One 2020; 15:e0215341. [PMID: 31945063 DOI: 10.1371/journal.pone.0215341] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 12/30/2019] [Indexed: 12/22/2022] Open
Abstract
Geobacter sulfurreducens was originally considered a strict anaerobe. However, this bacterium was later shown to not only tolerate exposure to oxygen but also to use it as terminal electron acceptor. Research performed has so far only revealed the general ability of G. sulfurreducens to reduce oxygen, but the oxygen uptake rate has not been quantified yet, nor has evidence been provided as to how the bacterium achieves oxygen reduction. Therefore, microaerobic growth of G. sulfurreducens was investigated here with better defined operating conditions as previously performed and a transcriptome analysis was performed to elucidate possible metabolic mechanisms important for oxygen reduction in G. sulfurreducens. The investigations revealed that cell growth with oxygen is possible to the same extent as with fumarate if the maximum specific oxygen uptake rate (sOUR) of 95 mgO2 gCDW-1 h-1 is not surpassed. Hereby, the entire amount of introduced oxygen is reduced. When oxygen concentrations are too high, cell growth is completely inhibited and there is no partial oxygen consumption. Transcriptome analysis suggests a menaquinol oxidase to be the enzyme responsible for oxygen reduction. Transcriptome analysis has further revealed three different survival strategies, depending on the oxygen concentration present. When prompted with small amounts of oxygen, G. sulfurreducens will try to escape the microaerobic area; if oxygen concentrations are higher, cells will focus on rapid and complete oxygen reduction coupled to cell growth; and ultimately cells will form protective layers if a complete reduction becomes impossible. The results presented here have important implications for understanding how G. sulfurreducens survives exposure to oxygen.
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Semenec L, Vergara IA, Laloo AE, Mathews ER, Bond PL, Franks AE. Enhanced Growth of Pilin-Deficient Geobacter sulfurreducens Mutants in Carbon Poor and Electron Donor Limiting Conditions. Microb Ecol 2019; 78:618-630. [PMID: 30759269 DOI: 10.1007/s00248-019-01316-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 01/01/2019] [Indexed: 06/09/2023]
Abstract
Geobacter sulfurreducens pili enable extracellular electron transfer and play a role in secretion of c-type cytochromes such as OmcZ. PilA-deficient mutants of G. sulfurreducens have previously been shown to accumulate cytochromes within their membranes. This cytochrome retaining phenotype allowed for enhanced growth of PilA-deficient mutants in electron donor and carbon-limited conditions where formate and fumarate are provided as the sole electron donor and acceptor with no supplementary carbon source. Conversely, wild-type G. sulfurreducens, which has normal secretion of cytochromes, has comparative limited growth in these conditions. This growth is further impeded for OmcZ-deficient and OmcS-deficient mutants. A PilB-deficient mutant which prevents pilin production but allows for secretion of OmcZ had moderate growth in these conditions, indicating a role for cytochrome localization to enabling survival in the electron donor and carbon-limited conditions. To determine which pathways enhanced growth using formate, Sequential Window Acquisition of all Theoretical Mass Spectra mass spectrometry (SWATH-MS) proteomics of formate adapted PilA-deficient mutants and acetate grown wild type was performed. PilA-deficient mutants had an overall decrease in tricarboxylic acid (TCA) cycle enzymes and significant upregulation of electron transport chain associated proteins including many c-type cytochromes and [NiFe]-hydrogenases. Whole genome sequencing of the mutants shows strong convergent evolution and emergence of genetic subpopulations during adaptation to growth on formate. The results described here suggest a role for membrane constrained c-type cytochromes to the enhancement of survival and growth in electron donor and carbon-limited conditions.
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Affiliation(s)
- Lucie Semenec
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia
| | - Ismael A Vergara
- Bioinformatics and Cancer Genomics, Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Andrew E Laloo
- Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Elizabeth R Mathews
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia
| | - Philip L Bond
- Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Ashley E Franks
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia.
- Centre for Future Landscapes, La Trobe University, Melbourne, Australia.
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Sun D, Wan X, Liu W, Xia X, Huang F, Wang A, Smith JA, Dang Y, Holmes DE. Characterization of the genome from Geobacter anodireducens, a strain with enhanced current production in bioelectrochemical systems. RSC Adv 2019; 9:25890-25899. [PMID: 35530078 PMCID: PMC9070056 DOI: 10.1039/c9ra02343g] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 07/20/2019] [Indexed: 11/21/2022] Open
Abstract
Geobacter anodireducens is unique in that it can generate high current densities in bioelectrochemical systems (BES) operating under high salt conditions. This ability is important for the development of BES treating high salt wastewater and microbial desalination cells. Therefore, the genome of G. anodireducens was characterized to identify proteins that might allow this strain to survive in high salt BES. Comparison to other Geobacter species revealed that 81 of its 87 c-type cytochromes had homologs in G. soli and G. sulfurreducens. Genes coding for many extracellular electron transfer proteins were also detected, including the outer membrane c-type cytochromes OmcS and OmcZ and the soluble c-type cytochrome PgcA. G. anodireducens also appears to have numerous membrane complexes involved in the translocation of protons and sodium ions and channels that provide protection against osmotic shock. In addition, it has more DNA repair genes than most Geobacter species, suggesting that it might be able to more rapidly repair DNA damage caused in high salt and low pH anode environments. Although this genomic analysis provides invaluable insight into mechanisms used by G. anodireducens to survive in high salt BES, genetic, transcriptomic, and proteomic studies will need to be done to validate their roles.
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Affiliation(s)
- Dan Sun
- Ocean College, Zhejiang University Zhoushan 316021 P. R. China
| | - Xinyuan Wan
- Ocean College, Zhejiang University Zhoushan 316021 P. R. China
| | - Wenzong Liu
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences Beijing 100084 P. R. China
| | - Xue Xia
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences Beijing 100084 P. R. China
| | - Fangliang Huang
- College of Life Sciences, Zhejiang University Hangzhou 310058 P. R. China
| | - Aijie Wang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences Beijing 100084 P. R. China
| | - Jessica A Smith
- Department of Biomolecular Sciences, Central Connecticut State University 1615 Stanley Street New Britain CT 06050 USA
| | - Yan Dang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science & Engineering, Beijing Forestry University 35 Tsinghua East Road Beijing 100083 China
| | - Dawn E Holmes
- Department of Physical and Biological Sciences, Western New England University 1215 Wilbraham Rd Springfield MA 01190 USA
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Abstract
The family Geobacteraceae, with its only valid genus Geobacter, comprises deltaproteobacteria ubiquitous in soil, sediments, and subsurface environments where metal reduction is an active process. Research for almost three decades has provided novel insights into environmental processes and biogeochemical reactions not previously known to be carried out by microorganisms. At the heart of the environmental roles played by Geobacter bacteria is their ability to integrate redox pathways and regulatory checkpoints that maximize growth efficiency with electron donors derived from the decomposition of organic matter while respiring metal oxides, particularly the often abundant oxides of ferric iron. This metabolic specialization is complemented by versatile metabolic reactions, respiratory chains, and sensory networks that allow specific members to adaptively respond to environmental cues to integrate organic and inorganic contaminants in their oxidative and reductive metabolism, respectively. Thus, Geobacteraceae are important members of the microbial communities that degrade hydrocarbon contaminants under iron-reducing conditions and that contribute, directly or indirectly, to the reduction of radionuclides, toxic metals, and oxidized species of nitrogen. Their ability to produce conductive pili as nanowires for discharging respiratory electrons to solid-phase electron acceptors and radionuclides, or for wiring cells in current-harvesting biofilms highlights the unique physiological traits that make these organisms attractive biological platforms for bioremediation, bioenergy, and bioelectronics application. Here we review some of the most notable physiological features described in Geobacter species since the first model representatives were recovered in pure culture. We provide a historical account of the environmental research that has set the foundation for numerous physiological studies and the laboratory tools that had provided novel insights into the role of Geobacter in the functioning of microbial communities from pristine and contaminated environments. We pay particular attention to latest research, both basic and applied, that has served to expand the field into new directions and to advance interdisciplinary knowledge. The electrifying physiology of Geobacter, it seems, is alive and well 30 years on.
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Shi Z. Methylome and Metabolome Analyses Reveal Adaptive Mechanisms in Geobacter sulfurreducens Grown on Different Terminal Electron Acceptors. J Proteome Res 2019; 18:1494-1502. [DOI: 10.1021/acs.jproteome.8b00763] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Zhenhua Shi
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
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18
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Jahan MI, Tobe R, Mihara H. Characterization of a Novel Porin-Like Protein, ExtI, from Geobacter sulfurreducens and Its Implication in the Reduction of Selenite and Tellurite. Int J Mol Sci 2018. [PMID: 29534491 PMCID: PMC5877670 DOI: 10.3390/ijms19030809] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The extI gene in Geobacter sulfurreducens encodes a putative outer membrane channel porin, which resides within a cluster of extHIJKLMNOPQS genes. This cluster is highly conserved across the Geobacteraceae and includes multiple putative c-type cytochromes. In silico analyses of the ExtI sequence, together with Western blot analysis and proteinase protection assays, showed that it is an outer membrane protein. The expression level of ExtI did not respond to changes in osmolality and phosphate starvation. An extI-deficient mutant did not show any significant impact on fumarate or Fe(III) citrate reduction or sensitivity to β-lactam antibiotics, as compared with those of the wild-type strain. However, extI deficiency resulted in a decreased ability to reduce selenite and tellurite. Heme staining analysis revealed that extI deficiency affects certain heme-containing proteins in the outer and inner membranes, which may cause a decrease in the ability to reduce selenite and tellurite. Based on these observations, we discuss possible roles for ExtI in selenite and tellurite reduction in G. sulfurreducens.
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Affiliation(s)
- Mst Ishrat Jahan
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
| | - Ryuta Tobe
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
| | - Hisaaki Mihara
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
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Tejedor-Sanz S, Quejigo JR, Berná A, Esteve-Núñez A. The Planktonic Relationship Between Fluid-Like Electrodes and Bacteria: Wiring in Motion. ChemSusChem 2017; 10:693-700. [PMID: 27860438 DOI: 10.1002/cssc.201601329] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 11/01/2016] [Indexed: 06/06/2023]
Abstract
We have explored a new concept in bacteria-electrode interaction based on the use of fluid-like electrodes and planktonic living cells. We show for the first time that living in a biofilm is not a strict requirement for Geobacter sulfurreducens to exchange electrons with an electrode. The growth of planktonic electroactive G. sulfurreducens could be supported by a fluid-like anode as soluble electron acceptors and with electron transfer rates similar to those reported for electroactive biofilms. This growth was maintained by uncoupling the charge (catabolism) and discharge (extracellular respiration) processes of the cells. Our results reveal a novel method to culture electroactive bacteria in which every single cell in the medium could be instantaneously wired to a fluid-like electrode. Direct extracellular electron transfer is occurring but with a new paradigm behind the bacteria-electrode interaction.
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Affiliation(s)
- Sara Tejedor-Sanz
- Department of Chemical Engineering, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
- Innovation and Technology Department, FCC Aqualia, S.A., Madrid, Spain
| | - Jose Rodrigo Quejigo
- Department of Chemical Engineering, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
| | - Antonio Berná
- IMDEA Water, Parque Tecnológico de Alcalá, Alcalá de Henares, Madrid, Spain
| | - Abraham Esteve-Núñez
- Department of Chemical Engineering, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
- IMDEA Water, Parque Tecnológico de Alcalá, Alcalá de Henares, Madrid, Spain
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Lancaster CRD, Betz YM, Heit S, Lafontaine MA. Transmembrane Electron and Proton Transfer in Diheme-Containing Succinate : Quinone Oxidoreductases. Isr J Chem 2017. [DOI: 10.1002/ijch.201600139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- C. Roy D. Lancaster
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
| | - Yamila M. Betz
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
| | - Sabine Heit
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
| | - Michael A. Lafontaine
- Department of Structural Biology; Center of Human and Molecular Biology (ZHMB); Saarland University; Faculty of Medicine Building 60 D-66421 Homburg (Saar) Germany
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Abstract
This study shows that Geobacter sulfurreducens grows on carbon monoxide (CO) as electron donor with fumarate as electron acceptor. Geobacter sulfurreducens was tolerant to high CO levels, with up to 150 kPa in the headspace tested. During growth, hydrogen was detected in very slight amounts (∼5 Pa). In assays with cell-free extract of cells grown with CO and fumarate, production of hydrogen from CO was not observed, and hydrogenase activity with benzyl viologen as electron acceptor was very low. Taken together, this suggested that CO is not utilized via hydrogen as intermediate. In the presence of CO, reduction of NADP+ was observed at a rate comparable to CO oxidation coupled to fumarate reduction in vivo. The G. sulfurreducens genome contains a single putative carbon monoxide dehydrogenase-encoding gene. The gene is part of a predicted operon also comprising a putative Fe–S cluster-binding subunit (CooF) and a FAD–NAD(P) oxidoreductase and is preceded by a putative CO-sensing transcription factor. This cluster may be involved in a novel pathway for CO oxidation, but further studies are necessary to ascertain this. Similar gene clusters are present in several other species belonging to the Deltaproteobacteria and Firmicutes, for which CO utilization is currently not known.
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Affiliation(s)
- Jeanine S Geelhoed
- Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, The Netherlands.
- NIOZ Royal Netherlands Institute for Sea Research, Korringaweg 7, 4401 NT, Yerseke, The Netherlands.
| | - Anne M Henstra
- Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, The Netherlands
- Centre for Biomolecular Sciences, University of Nottingham, University Park, NG7 2EF, Nottingham, UK
| | - Alfons J M Stams
- Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB, Wageningen, The Netherlands
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Estevez-Canales M, Kuzume A, Borjas Z, Füeg M, Lovley D, Wandlowski T, Esteve-Núñez A. A severe reduction in the cytochrome C content of Geobacter sulfurreducens eliminates its capacity for extracellular electron transfer. Environ Microbiol Rep 2015; 7:219-226. [PMID: 25348891 DOI: 10.1111/1758-2229.12230] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 09/23/2014] [Indexed: 06/04/2023]
Abstract
The ability of Geobacter species to transfer electrons outside the cell enables them to play an important role in a number of biogeochemical and bioenergy processes. Gene deletion studies have implicated periplasmic and outer-surface c-type cytochromes in this extracellular electron transfer. However, even when as many as five c-type cytochrome genes have been deleted, some capacity for extracellular electron transfer remains. In order to evaluate the role of c-type cytochromes in extracellular electron transfer, Geobacter sulfurreducens was grown in a low-iron medium that included the iron chelator (2,2'-bipyridine) to further sequester iron. Haem-staining revealed that the cytochrome content of cells grown in this manner was 15-fold lower than in cells exposed to a standard iron-containing medium. The low cytochrome abundance was confirmed by in situ nanoparticle-enhanced Raman spectroscopy (NERS). The cytochrome-depleted cells reduced fumarate to succinate as well as the cytochrome-replete cells do, but were unable to reduce Fe(III) citrate or to exchange electrons with a graphite electrode. These results demonstrate that c-type cytochromes are essential for extracellular electron transfer by G. sulfurreducens. The strategy for growing cytochrome-depleted G. sulfurreducens will also greatly aid future physiological studies of Geobacter species and other microorganisms capable of extracellular electron transfer.
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Affiliation(s)
- Marta Estevez-Canales
- Department of Chemical Engineering, University of Alcalá, Alcalá de Henares, Madrid, Spain
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Rose ND, Regan JM. Changes in phosphorylation of adenosine phosphate and redox state of nicotinamide-adenine dinucleotide (phosphate) in Geobacter sulfurreducens in response to electron acceptor and anode potential variation. Bioelectrochemistry 2015; 106:213-20. [PMID: 25857596 DOI: 10.1016/j.bioelechem.2015.03.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/03/2015] [Accepted: 03/16/2015] [Indexed: 01/28/2023]
Abstract
Geobacter sulfurreducens is one of the dominant bacterial species found in biofilms growing on anodes in bioelectrochemical systems. The intracellular concentrations of reduced and oxidized forms of nicotinamide-adenine dinucleotide (NADH and NAD(+), respectively) and nicotinamide-adenine dinucleotide phosphate (NADPH and NADP(+), respectively) as well as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) were measured in G. sulfurreducens using fumarate, Fe(III)-citrate, or anodes poised at different potentials (110, 10, -90, and -190 mV (vs. SHE)) as the electron acceptor. The ratios of CNADH/CNAD+ (0.088±0.022) and CNADPH/CNADP+ (0.268±0.098) were similar under all anode potentials tested and with Fe(III)-citrate (reduced extracellularly). Both ratios significantly increased with fumarate as the electron acceptor (0.331±0.094 for NAD and 1.96±0.37 for NADP). The adenylate energy charge (the fraction of phosphorylation in intracellular adenosine phosphates) was maintained near 0.47 under almost all conditions. Anode-growing biofilms demonstrated a significantly higher molar ratio of ATP/ADP relative to suspended cultures grown on fumarate or Fe(III)-citrate. These results provide evidence that the cellular location of reduction and not the redox potential of the electron acceptor controls the intracellular redox potential in G. sulfurreducens and that biofilm growth alters adenylate phosphorylation.
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Affiliation(s)
- Nicholas D Rose
- College of Engineering, Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, State College, PA 16802, USA.
| | - John M Regan
- College of Engineering, Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, State College, PA 16802, USA.
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Muhamadali H, Xu Y, Ellis DI, Allwood JW, Rattray NJ, Correa E, Alrabiah H, Lloyd JR, Goodacre R. Metabolic Profiling of Geobacter sulfurreducens during Industrial Bioprocess Scale-Up. Appl Environ Microbiol 2015; 81:3288-98. [PMID: 25746987 DOI: 10.1128/AEM.00294-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 02/24/2015] [Indexed: 11/20/2022] Open
Abstract
During the industrial scale-up of bioprocesses it is important to establish that the biological system has not changed significantly when moving from small laboratory-scale shake flasks or culturing bottles to an industrially relevant production level. Therefore, during upscaling of biomass production for a range of metal transformations, including the production of biogenic magnetite nanoparticles by Geobacter sulfurreducens, from 100-ml bench-scale to 5-liter fermentors, we applied Fourier transform infrared (FTIR) spectroscopy as a metabolic fingerprinting approach followed by the analysis of bacterial cell extracts by gas chromatography-mass spectrometry (GC-MS) for metabolic profiling. FTIR results clearly differentiated between the phenotypic changes associated with different growth phases as well as the two culturing conditions. Furthermore, the clustering patterns displayed by multivariate analysis were in agreement with the turbidimetric measurements, which displayed an extended lag phase for cells grown in a 5-liter bioreactor (24 h) compared to those grown in 100-ml serum bottles (6 h). GC-MS analysis of the cell extracts demonstrated an overall accumulation of fumarate during the lag phase under both culturing conditions, coinciding with the detected concentrations of oxaloacetate, pyruvate, nicotinamide, and glycerol-3-phosphate being at their lowest levels compared to other growth phases. These metabolites were overlaid onto a metabolic network of G. sulfurreducens, and taking into account the levels of these metabolites throughout the fermentation process, the limited availability of oxaloacetate and nicotinamide would seem to be the main metabolic bottleneck resulting from this scale-up process. Additional metabolite-feeding experiments were carried out to validate the above hypothesis. Nicotinamide supplementation (1 mM) did not display any significant effects on the lag phase of G. sulfurreducens cells grown in the 100-ml serum bottles. However, it significantly improved the growth behavior of cells grown in the 5-liter bioreactor by reducing the lag phase from 24 h to 6 h, while providing higher yield than in the 100-ml serum bottles.
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Feist AM, Nagarajan H, Rotaru AE, Tremblay PL, Zhang T, Nevin KP, Lovley DR, Zengler K. Constraint-based modeling of carbon fixation and the energetics of electron transfer in Geobacter metallireducens. PLoS Comput Biol 2014; 10:e1003575. [PMID: 24762737 PMCID: PMC3998878 DOI: 10.1371/journal.pcbi.1003575] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 03/05/2014] [Indexed: 11/18/2022] Open
Abstract
Geobacter species are of great interest for environmental and biotechnology applications as they can carry out direct electron transfer to insoluble metals or other microorganisms and have the ability to assimilate inorganic carbon. Here, we report on the capability and key enabling metabolic machinery of Geobacter metallireducens GS-15 to carry out CO2 fixation and direct electron transfer to iron. An updated metabolic reconstruction was generated, growth screens on targeted conditions of interest were performed, and constraint-based analysis was utilized to characterize and evaluate critical pathways and reactions in G. metallireducens. The novel capability of G. metallireducens to grow autotrophically with formate and Fe(III) was predicted and subsequently validated in vivo. Additionally, the energetic cost of transferring electrons to an external electron acceptor was determined through analysis of growth experiments carried out using three different electron acceptors (Fe(III), nitrate, and fumarate) by systematically isolating and examining different parts of the electron transport chain. The updated reconstruction will serve as a knowledgebase for understanding and engineering Geobacter and similar species.
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Affiliation(s)
- Adam M. Feist
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
- * E-mail: (AMF); (KZ)
| | - Harish Nagarajan
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Amelia-Elena Rotaru
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Pier-Luc Tremblay
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Tian Zhang
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Kelly P. Nevin
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Derek R. Lovley
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Karsten Zengler
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
- * E-mail: (AMF); (KZ)
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Kim SJ, Park SJ, Cha IT, Min D, Kim JS, Chung WH, Chae JC, Jeon CO, Rhee SK. Metabolic versatility of toluene-degrading, iron-reducing bacteria in tidal flat sediment, characterized by stable isotope probing-based metagenomic analysis. Environ Microbiol 2013; 16:189-204. [DOI: 10.1111/1462-2920.12277] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 09/04/2013] [Accepted: 09/06/2013] [Indexed: 11/28/2022]
Affiliation(s)
- So-Jeong Kim
- Department of Microbiology; Chungbuk National University; Cheongju 361-763 Korea
| | - Soo-Je Park
- Department of Biology; Jeju National University; Jeju 690-756 Korea
| | - In-Tae Cha
- Department of Microbiology; Chungbuk National University; Cheongju 361-763 Korea
| | - Deullae Min
- Center for Gas Analysis; Korea Research Institute of Standards and Science; 267 Gajeong-ro, Yuseong-gu Daejeon 305-340 Korea
| | - Jin-Seog Kim
- Center for Gas Analysis; Korea Research Institute of Standards and Science; 267 Gajeong-ro, Yuseong-gu Daejeon 305-340 Korea
| | - Won-Hyung Chung
- Korean Bioinformation Center; Korean Research Institute of Bioscience and Bioengineering; Daejeon 305-806 Korea
| | - Jong-Chan Chae
- Division of Biotechnology; Chonbuk National University; Iksan 570-752 Korea
| | - Che Ok Jeon
- School of Biological Sciences; Chung-Ang University; Seoul 156-756 Korea
| | - Sung-Keun Rhee
- Department of Microbiology; Chungbuk National University; Cheongju 361-763 Korea
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Prakash D, Gabani P, Chandel AK, Ronen Z, Singh OV. Bioremediation: a genuine technology to remediate radionuclides from the environment. Microb Biotechnol 2013; 6:349-60. [PMID: 23617701 PMCID: PMC3917470 DOI: 10.1111/1751-7915.12059] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 03/19/2013] [Accepted: 03/25/2013] [Indexed: 12/01/2022] Open
Abstract
Radionuclides in the environment are a major human and environmental health concern. Like the Chernobyl disaster of 1986, the Fukushima Daiichi nuclear disaster in 2011 is once again causing damage to the environment: a large quantity of radioactive waste is being generated and dumped into the environment, and if the general population is exposed to it, may cause serious life-threatening disorders. Bioremediation has been viewed as the ecologically responsible alternative to environmentally destructive physical remediation. Microorganisms carry endogenous genetic, biochemical and physiological properties that make them ideal agents for pollutant remediation in soil and groundwater. Attempts have been made to develop native or genetically engineered (GE) microbes for the remediation of environmental contaminants including radionuclides. Microorganism-mediated bioremediation can affect the solubility, bioavailability and mobility of radionuclides. Therefore, we aim to unveil the microbial-mediated mechanisms for biotransformation of radionuclides under various environmental conditions as developing strategies for waste management of radionuclides. A discussion follows of '-omics'-integrated genomics and proteomics technologies, which can be used to trace the genes and proteins of interest in a given microorganism towards a cell-free bioremediation strategy.
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Affiliation(s)
- Dhan Prakash
- Institute of Microbial Technology (CSIR), Sector 39-A, Chandigarh, 160036, India
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Lancaster CRD. The di-heme family of respiratory complex II enzymes. Biochim Biophys Acta 2013; 1827:679-87. [PMID: 23466335 DOI: 10.1016/j.bbabio.2013.02.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 02/22/2013] [Accepted: 02/22/2013] [Indexed: 01/28/2023]
Abstract
The di-heme family of succinate:quinone oxidoreductases is of particular interest, because its members support electron transfer across the biological membranes in which they are embedded. In the case of the di-heme-containing succinate:menaquinone reductase (SQR) from Gram-positive bacteria and other menaquinone-containing bacteria, this results in an electrogenic reaction. This is physiologically relevant in that it allows the transmembrane electrochemical proton potential Δp to drive the endergonic oxidation of succinate by menaquinone. In the case of the reverse reaction, menaquinol oxidation by fumarate, catalysed by the di-heme-containing quinol:fumarate reductase (QFR), evidence has been obtained that this electrogenic electron transfer reaction is compensated by proton transfer via a both novel and essential transmembrane proton transfer pathway ("E-pathway"). Although the reduction of fumarate by menaquinol is exergonic, it is obviously not exergonic enough to support the generation of a Δp. This compensatory "E-pathway" appears to be required by all di-heme-containing QFR enzymes and results in the overall reaction being electroneutral. In addition to giving a brief overview of progress in the characterization of other members of this diverse family, this contribution summarizes key evidence and progress in identifying constituents of the "E-pathway" within the framework of the crystal structure of the QFR from the anaerobic epsilon-proteobacterium Wolinella succinogenes at 1.78Å resolution. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.
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Affiliation(s)
- C Roy D Lancaster
- Department of Structural Biology, Saarland University, Homburg, Germany.
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Aklujkar M, Coppi MV, Leang C, Kim BC, Chavan MA, Perpetua LA, Giloteaux L, Liu A, Holmes DE. Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens. Microbiology (Reading) 2013; 159:515-535. [PMID: 23306674 DOI: 10.1099/mic.0.064089-0] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Whole-genome microarray analysis of Geobacter sulfurreducens grown on insoluble Fe(III) oxide or Mn(IV) oxide versus soluble Fe(III) citrate revealed significantly different expression patterns. The most upregulated genes, omcS and omcT, encode cell-surface c-type cytochromes, OmcS being required for Fe(III) and Mn(IV) oxide reduction. Other electron transport genes upregulated on both metal oxides included genes encoding putative menaquinol : ferricytochrome c oxidoreductase complexes Cbc4 and Cbc5, periplasmic c-type cytochromes Dhc2 and PccF, outer membrane c-type cytochromes OmcC, OmcG and OmcV, multicopper oxidase OmpB, the structural components of electrically conductive pili, PilA-N and PilA-C, and enzymes that detoxify reactive oxygen/nitrogen species. Genes upregulated on Fe(III) oxide encode putative menaquinol : ferricytochrome c oxidoreductase complexes Cbc3 and Cbc6, periplasmic c-type cytochromes, including PccG and PccJ, and outer membrane c-type cytochromes, including OmcA, OmcE, OmcH, OmcL, OmcN, OmcO and OmcP. Electron transport genes upregulated on Mn(IV) oxide encode periplasmic c-type cytochromes PccR, PgcA, PpcA and PpcD, outer membrane c-type cytochromes OmaB/OmaC, OmcB and OmcZ, multicopper oxidase OmpC and menaquinone-reducing enzymes. Genetic studies indicated that MacA, OmcB, OmcF, OmcG, OmcH, OmcI, OmcJ, OmcM, OmcV and PccH, the putative Cbc5 complex subunit CbcC and the putative Cbc3 complex subunit CbcV are important for reduction of Fe(III) oxide but not essential for Mn(IV) oxide reduction. Gene expression patterns for Geobacter uraniireducens were similar. These results demonstrate that the physiology of Fe(III)-reducing bacteria differs significantly during growth on different insoluble and soluble electron acceptors and emphasize the importance of c-type cytochromes for extracellular electron transfer in G. sulfurreducens.
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Affiliation(s)
- M Aklujkar
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - M V Coppi
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - C Leang
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - B C Kim
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - M A Chavan
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - L A Perpetua
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - L Giloteaux
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - A Liu
- Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - D E Holmes
- Department of Physical and Biological Sciences, Western New England University, Springfield, MA 01119, USA
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Aklujkar M, Haveman SA, DiDonato R, Chertkov O, Han CS, Land ML, Brown P, Lovley DR. The genome of Pelobacter carbinolicus reveals surprising metabolic capabilities and physiological features. BMC Genomics 2012; 13:690. [PMID: 23227809 PMCID: PMC3543383 DOI: 10.1186/1471-2164-13-690] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 11/22/2012] [Indexed: 11/24/2022] Open
Abstract
Background The bacterium Pelobacter carbinolicus is able to grow by fermentation, syntrophic hydrogen/formate transfer, or electron transfer to sulfur from short-chain alcohols, hydrogen or formate; it does not oxidize acetate and is not known to ferment any sugars or grow autotrophically. The genome of P. carbinolicus was sequenced in order to understand its metabolic capabilities and physiological features in comparison with its relatives, acetate-oxidizing Geobacter species. Results Pathways were predicted for catabolism of known substrates: 2,3-butanediol, acetoin, glycerol, 1,2-ethanediol, ethanolamine, choline and ethanol. Multiple isozymes of 2,3-butanediol dehydrogenase, ATP synthase and [FeFe]-hydrogenase were differentiated and assigned roles according to their structural properties and genomic contexts. The absence of asparagine synthetase and the presence of a mutant tRNA for asparagine encoded among RNA-active enzymes suggest that P. carbinolicus may make asparaginyl-tRNA in a novel way. Catabolic glutamate dehydrogenases were discovered, implying that the tricarboxylic acid (TCA) cycle can function catabolically. A phosphotransferase system for uptake of sugars was discovered, along with enzymes that function in 2,3-butanediol production. Pyruvate:ferredoxin/flavodoxin oxidoreductase was identified as a potential bottleneck in both the supply of oxaloacetate for oxidation of acetate by the TCA cycle and the connection of glycolysis to production of ethanol. The P. carbinolicus genome was found to encode autotransporters and various appendages, including three proteins with similarity to the geopilin of electroconductive nanowires. Conclusions Several surprising metabolic capabilities and physiological features were predicted from the genome of P. carbinolicus, suggesting that it is more versatile than anticipated.
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Affiliation(s)
- Muktak Aklujkar
- University of Massachusetts Amherst, Amherst, MA 01003, USA.
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Tremblay PL, Aklujkar M, Leang C, Nevin KP, Lovley D. A genetic system for Geobacter metallireducens: role of the flagellin and pilin in the reduction of Fe(III) oxide. Environ Microbiol Rep 2012; 4:82-88. [PMID: 23757233 DOI: 10.1111/j.1758-2229.2011.00305.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Geobacter metallireducens is an important model organism for many novel aspects of extracellular electron exchange and the anaerobic degradation of aromatic compounds, but studies of its physiology have been limited by a lack of techniques for gene deletion and replacement. Therefore, a genetic system was developed for G. metallireducens by making a number of modifications in the previously described approach for homologous recombination in Geobacter sulfurreducens. Critical modifications included, among others, a 3.5-fold increased in the quantity of electrotransformed linear DNA and the harvesting of cells at early-log. The Cre-lox recombination system was used to remove an antibiotic resistance cassette from the G. metallireducens chromosome permitting the generation of multiple mutations in the same strain. Deletion of the gene fliC, which encodes the flagellin protein, resulted in a strain that did not produce flagella, was non-motile, and was defective for the reduction of insoluble Fe(III). Deletion of pilA, which encodes the structural protein of the type IV pili, inhibited the production of lateral pili as well as Fe(III) oxide reduction and electron transfer to an electrode. These results demonstrate the importance of flagella and pili in the reduction of insoluble Fe(III) by G. metallireducens and provide methods for additional genetic-based approaches for the study of G. metallireducens.
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Affiliation(s)
- Pier-Luc Tremblay
- Department of Microbiology, University of Massachusetts, Amherst, MA, USA
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Tremblay PL, Summers ZM, Glaven RH, Nevin KP, Zengler K, Barrett CL, Qiu Y, Palsson BO, Lovley DR. A c-type cytochrome and a transcriptional regulator responsible for enhanced extracellular electron transfer in Geobacter sulfurreducens revealed by adaptive evolution. Environ Microbiol 2011; 13:13-23. [PMID: 20636372 DOI: 10.1111/j.1462-2920.2010.02302.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The stimulation of subsurface microbial metabolism often associated with engineered bioremediation of groundwater contaminants presents subsurface microorganisms, which are adapted for slow growth and metabolism in the subsurface, with new selective pressures. In order to better understand how Geobacter species might adapt to selective pressure for faster metal reduction in the subsurface, Geobacter sulfurreducens was put under selective pressure for rapid Fe(III) oxide reduction. The genomes of two resultant strains with rates of Fe(III) oxide reduction that were 10-fold higher than those of the parent strain were resequenced. Both strains contain either a single base-pair change or a 1 nucleotide insertion in a GEMM riboswitch upstream of GSU1761, a gene coding for the periplasmic c-type cytochrome designated PgcA. GSU1771, a gene coding for a SARP regulator, was also mutated in both strains. Introduction of either of the GEMM riboswitch mutations upstream of pgcA in the wild-type increased the abundance of pgcA transcripts, consistent with increased expression of pgcA in the adapted strains. One of the mutations doubled the rate of Fe(III) oxide reduction. Interruption of GSU1771 doubled the Fe(III) oxide reduction rate. This was associated with an increased in expression of pilA, the gene encoding the structural protein for the pili thought to function as microbial nanowires. The combination of the GSU1771 interruption with either of the pgcA mutations resulted in a strain that reduced Fe(III) as fast as the comparable adapted strain. These results suggest that the accumulation of a small number of beneficial mutations under selective pressure, similar to that potentially present during bioremediation, can greatly enhance the capacity for Fe(III) oxide reduction in G. sulfurreducens. Furthermore, the results emphasize the importance of the c-type cytochrome PgcA and pili in Fe(III) oxide reduction and demonstrate how adaptive evolution studies can aid in the elucidation of complex mechanisms, such as extracellular electron transfer.
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Affiliation(s)
- Pier-Luc Tremblay
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Zarath M Summers
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Richard H Glaven
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Kelly P Nevin
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Karsten Zengler
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Christian L Barrett
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Yu Qiu
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Bernhard O Palsson
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Derek R Lovley
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
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Pons L, Délia ML, Bergel A. Effect of surface roughness, biofilm coverage and biofilm structure on the electrochemical efficiency of microbial cathodes. Bioresour Technol 2011; 102:2678-2683. [PMID: 21131196 DOI: 10.1016/j.biortech.2010.10.138] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 10/26/2010] [Accepted: 10/29/2010] [Indexed: 05/30/2023]
Abstract
Biofilms of Geobacter sulfurreducens were formed under chronoamperometry at -0.5 V and -0.6 V vs. Ag/AgCl on stainless steel cathodes and tested for fumarate reduction. Increasing the surface roughness Ra from 2.0 μm to 4.0 μm increased currents by a factor of 1.6. The overall current density increased with biofilm coverage. When the current density was calculated with respect to the biofilm-coated area only, values up to 280 A/m(2) were derived. These values decreased with biofilm coverage and indicated that isolated cells or small colonies locally provide higher current density than dense colonies. Steel composition affected the current values because of differences in biofilm structure and electron transfer rates. Biofilms formed under polarisation revealed better electrochemical characteristics than biofilm developed at open circuit. This work opens up new guidelines for the design of microbial cathodes: a uniform carpet of isolated bacteria or small colonies should be targeted, avoiding the formation of large colonies.
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Affiliation(s)
- L Pons
- Laboratoire de Génie Chimique, CNRS-Université de Toulouse, Toulouse, France
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Lovley DR, Ueki T, Zhang T, Malvankar NS, Shrestha PM, Flanagan KA, Aklujkar M, Butler JE, Giloteaux L, Rotaru AE, Holmes DE, Franks AE, Orellana R, Risso C, Nevin KP. Geobacter: the microbe electric's physiology, ecology, and practical applications. Adv Microb Physiol 2011; 59:1-100. [PMID: 22114840 DOI: 10.1016/b978-0-12-387661-4.00004-5] [Citation(s) in RCA: 380] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Geobacter species specialize in making electrical contacts with extracellular electron acceptors and other organisms. This permits Geobacter species to fill important niches in a diversity of anaerobic environments. Geobacter species appear to be the primary agents for coupling the oxidation of organic compounds to the reduction of insoluble Fe(III) and Mn(IV) oxides in many soils and sediments, a process of global biogeochemical significance. Some Geobacter species can anaerobically oxidize aromatic hydrocarbons and play an important role in aromatic hydrocarbon removal from contaminated aquifers. The ability of Geobacter species to reductively precipitate uranium and related contaminants has led to the development of bioremediation strategies for contaminated environments. Geobacter species produce higher current densities than any other known organism in microbial fuel cells and are common colonizers of electrodes harvesting electricity from organic wastes and aquatic sediments. Direct interspecies electron exchange between Geobacter species and syntrophic partners appears to be an important process in anaerobic wastewater digesters. Functional and comparative genomic studies have begun to reveal important aspects of Geobacter physiology and regulation, but much remains unexplored. Quantifying key gene transcripts and proteins of subsurface Geobacter communities has proven to be a powerful approach to diagnose the in situ physiological status of Geobacter species during groundwater bioremediation. The growth and activity of Geobacter species in the subsurface and their biogeochemical impact under different environmental conditions can be predicted with a systems biology approach in which genome-scale metabolic models are coupled with appropriate physical/chemical models. The proficiency of Geobacter species in transferring electrons to insoluble minerals, electrodes, and possibly other microorganisms can be attributed to their unique "microbial nanowires," pili that conduct electrons along their length with metallic-like conductivity. Surprisingly, the abundant c-type cytochromes of Geobacter species do not contribute to this long-range electron transport, but cytochromes are important for making the terminal electrical connections with Fe(III) oxides and electrodes and also function as capacitors, storing charge to permit continued respiration when extracellular electron acceptors are temporarily unavailable. The high conductivity of Geobacter pili and biofilms and the ability of biofilms to function as supercapacitors are novel properties that might contribute to the field of bioelectronics. The study of Geobacter species has revealed a remarkable number of microbial physiological properties that had not previously been described in any microorganism. Further investigation of these environmentally relevant and physiologically unique organisms is warranted.
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Affiliation(s)
- Derek R Lovley
- Department of Microbiology and Environmental Biotechnology Center, University of Massachusetts, Amherst, Massachusetts, USA
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Yang TH, Coppi MV, Lovley DR, Sun J. Metabolic response of Geobacter sulfurreducens towards electron donor/acceptor variation. Microb Cell Fact 2010; 9:90. [PMID: 21092215 PMCID: PMC3002917 DOI: 10.1186/1475-2859-9-90] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 11/22/2010] [Indexed: 11/15/2022] Open
Abstract
Background Geobacter sulfurreducens is capable of coupling the complete oxidation of organic compounds to iron reduction. The metabolic response of G. sulfurreducens towards variations in electron donors (acetate, hydrogen) and acceptors (Fe(III), fumarate) was investigated via 13C-based metabolic flux analysis. We examined the 13C-labeling patterns of proteinogenic amino acids obtained from G. sulfurreducens cultured with 13C-acetate. Results Using 13C-based metabolic flux analysis, we observed that donor and acceptor variations gave rise to differences in gluconeogenetic initiation, tricarboxylic acid cycle activity, and amino acid biosynthesis pathways. Culturing G. sulfurreducens cells with Fe(III) as the electron acceptor and acetate as the electron donor resulted in pyruvate as the primary carbon source for gluconeogenesis. When fumarate was provided as the electron acceptor and acetate as the electron donor, the flux analysis suggested that fumarate served as both an electron acceptor and, in conjunction with acetate, a carbon source. Growth on fumarate and acetate resulted in the initiation of gluconeogenesis by phosphoenolpyruvate carboxykinase and a slightly elevated flux through the oxidative tricarboxylic acid cycle as compared to growth with Fe(III) as the electron acceptor. In addition, the direction of net flux between acetyl-CoA and pyruvate was reversed during growth on fumarate relative to Fe(III), while growth in the presence of Fe(III) and acetate which provided hydrogen as an electron donor, resulted in decreased flux through the tricarboxylic acid cycle. Conclusions We gained detailed insight into the metabolism of G. sulfurreducens cells under various electron donor/acceptor conditions using 13C-based metabolic flux analysis. Our results can be used for the development of G. sulfurreducens as a chassis for a variety of applications including bioremediation and renewable biofuel production.
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Affiliation(s)
- Tae Hoon Yang
- Genomatica, Inc., 10520 Wateridge Circle, San Diego, CA 92121, USA.
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Aklujkar M, Lovley DR. Interference with histidyl-tRNA synthetase by a CRISPR spacer sequence as a factor in the evolution of Pelobacter carbinolicus. BMC Evol Biol 2010; 10:230. [PMID: 20667132 PMCID: PMC2923632 DOI: 10.1186/1471-2148-10-230] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 07/28/2010] [Indexed: 11/21/2022] Open
Abstract
Background Pelobacter carbinolicus, a bacterium of the family Geobacteraceae, cannot reduce Fe(III) directly or produce electricity like its relatives. How P. carbinolicus evolved is an intriguing problem. The genome of P. carbinolicus contains clustered regularly interspaced short palindromic repeats (CRISPR) separated by unique spacer sequences, which recent studies have shown to produce RNA molecules that interfere with genes containing identical sequences. Results CRISPR spacer #1, which matches a sequence within hisS, the histidyl-tRNA synthetase gene of P. carbinolicus, was shown to be expressed. Phylogenetic analysis and genetics demonstrated that a gene paralogous to hisS in the genomes of Geobacteraceae is unlikely to compensate for interference with hisS. Spacer #1 inhibited growth of a transgenic strain of Geobacter sulfurreducens in which the native hisS was replaced with that of P. carbinolicus. The prediction that interference with hisS would result in an attenuated histidyl-tRNA pool insufficient for translation of proteins with multiple closely spaced histidines, predisposing them to mutation and elimination during evolution, was investigated by comparative genomics of P. carbinolicus and related species. Several ancestral genes with high histidine demand have been lost or modified in the P. carbinolicus lineage, providing an explanation for its physiological differences from other Geobacteraceae. Conclusions The disappearance of multiheme c-type cytochromes and other genes typical of a metal-respiring ancestor from the P. carbinolicus lineage may be the consequence of spacer #1 interfering with hisS, a condition that can be reproduced in a heterologous host. This is the first successful co-introduction of an active CRISPR spacer and its target in the same cell, the first application of a chimeric CRISPR construct consisting of a spacer from one species in the context of repeats of another species, and the first report of a potential impact of CRISPR on genome-scale evolution by interference with an essential gene.
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Affiliation(s)
- Muktak Aklujkar
- University of Massachusetts Amherst, Amherst, MA 01003, USA.
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Miller LD, Mosher JJ, Venkateswaran A, Yang ZK, Palumbo AV, Phelps TJ, Podar M, Schadt CW, Keller M. Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments. BMC Microbiol 2010; 10:149. [PMID: 20497531 PMCID: PMC2906461 DOI: 10.1186/1471-2180-10-149] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 05/24/2010] [Indexed: 01/03/2023] Open
Abstract
Background Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes. For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. The three species microbial community was comprised of Clostridium cellulolyticum, Desulfovibrio vulgaris Hildenborough, and Geobacter sulfurreducens and was grown under continuous culture conditions. Cellobiose served as the carbon and energy source for C. cellulolyticum, whereas D. vulgaris and G. sulfurreducens derived carbon and energy from the metabolic products of cellobiose fermentation and were provided with sulfate and fumarate respectively as electron acceptors. Results qPCR monitoring of the culture revealed C. cellulolyticum to be dominant as expected and confirmed the presence of D. vulgaris and G. sulfurreducens. Proposed metabolic modeling of carbon and electron flow of the three-species community indicated that the growth of C. cellulolyticum and D. vulgaris were electron donor limited whereas G. sulfurreducens was electron acceptor limited. Conclusions The results demonstrate that C. cellulolyticum, D. vulgaris, and G. sulfurreducens can be grown in coculture in a continuous culture system in which D. vulgaris and G. sulfurreducens are dependent upon the metabolic byproducts of C. cellulolyticum for nutrients. This represents a step towards developing a tractable model ecosystem comprised of members representing the functional groups of a trophic network.
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Affiliation(s)
- Lance D Miller
- Biosciences and Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Busalmen JP, Esteve-Nuñez A, Berná A, Feliu JM. ATR-SEIRAs characterization of surface redox processes in G. sulfurreducens. Bioelectrochemistry 2010; 78:25-9. [DOI: 10.1016/j.bioelechem.2009.04.011] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 04/20/2009] [Accepted: 04/30/2009] [Indexed: 10/20/2022]
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Guccione E, Hitchcock A, Hall SJ, Mulholland F, Shearer N, van Vliet AHM, Kelly DJ. Reduction of fumarate, mesaconate and crotonate by Mfr, a novel oxygen-regulated periplasmic reductase inCampylobacter jejuni. Environ Microbiol 2010; 12:576-91. [DOI: 10.1111/j.1462-2920.2009.02096.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Srinivasan K, Mahadevan R. Characterization of proton production and consumption associated with microbial metabolism. BMC Biotechnol 2010; 10:2. [PMID: 20089195 PMCID: PMC2831035 DOI: 10.1186/1472-6750-10-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 01/20/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Production or consumption of protons in growth medium during microbial metabolism plays an important role in determining the pH of the environment. Such pH changes resulting from microbial metabolism may influence the geochemical speciation of many elements in subsurface environments. Protons produced or consumed during microbial growth were measured by determining the amount of acid or base added in a 5 L batch bioreactor equipped with pH control for different species including Escherichia coli, Geobacter sulfurreducens, and Geobacter metallireducens. RESULTS An in silico model was used to predict the proton secretion or consumption rates and the results were compared with the data. The data was found to confirm predictions of proton consumption during aerobic growth of E. coli with acetate as the carbon source. However, in contrast to proton consumption observed during aerobic growth of E. coli with acetate, proton secretion was observed during growth of Geobacter species with acetate as the donor and Fe(III) as the extracellular electron acceptor. CONCLUSIONS In this study, we have also shown that the final pH of the medium can be either acidic or basic depending on the choice of the electron acceptor for the same electron donor. In all cases, the in silico model could predict qualitatively the proton production/consumption rates obtained from the experimental data. Therefore, measurements of pH equivalents generated or consumed during growth can help characterize the microbial physiology further and can be valuable for optimizing practical applications such as microbial fuel cells, where growth associated pH changes can limit current generation rates.
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Affiliation(s)
- Karthikeyan Srinivasan
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S3E5, Canada
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Butler JE, Young ND, Lovley DR. Evolution of electron transfer out of the cell: comparative genomics of six Geobacter genomes. BMC Genomics 2010; 11:40. [PMID: 20078895 DOI: 10.1186/1471-2164-11-40] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 01/17/2010] [Indexed: 12/14/2022] Open
Abstract
Background Geobacter species grow by transferring electrons out of the cell - either to Fe(III)-oxides or to man-made substances like energy-harvesting electrodes. Study of Geobacter sulfurreducens has shown that TCA cycle enzymes, inner-membrane respiratory enzymes, and periplasmic and outer-membrane cytochromes are required. Here we present comparative analysis of six Geobacter genomes, including species from the clade that predominates in the subsurface. Conservation of proteins across the genomes was determined to better understand the evolution of Geobacter species and to create a metabolic model applicable to subsurface environments. Results The results showed that enzymes for acetate transport and oxidation, and for proton transport across the inner membrane were well conserved. An NADH dehydrogenase, the ATP synthase, and several TCA cycle enzymes were among the best conserved in the genomes. However, most of the cytochromes required for Fe(III)-reduction were not, including many of the outer-membrane cytochromes. While conservation of cytochromes was poor, an abundance and diversity of cytochromes were found in every genome, with duplications apparent in several species. Conclusions These results indicate there is a common pathway for acetate oxidation and energy generation across the family and in the last common ancestor. They also suggest that while cytochromes are important for extracellular electron transport, the path of electrons across the periplasm and outer membrane is variable. This combination of abundant cytochromes with weak sequence conservation suggests they may not be specific terminal reductases, but rather may be important in their heme-bearing capacity, as sinks for electrons between the inner-membrane electron transport chain and the extracellular acceptor.
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Ueki T, Lovley DR. Genome-wide gene regulation of biosynthesis and energy generation by a novel transcriptional repressor in Geobacter species. Nucleic Acids Res 2009; 38:810-21. [PMID: 19939938 PMCID: PMC2817479 DOI: 10.1093/nar/gkp1085] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Geobacter species play important roles in bioremediation of contaminated environments and in electricity production from waste organic matter in microbial fuel cells. To better understand physiology of Geobacter species, expression and function of citrate synthase, a key enzyme in the TCA cycle that is important for organic acid oxidation in Geobacter species, was investigated. Geobacter sulfurreducens did not require citrate synthase for growth with hydrogen as the electron donor and fumarate as the electron acceptor. Expression of the citrate synthase gene, gltA, was repressed by a transcription factor under this growth condition. Functional and comparative genomics approaches, coupled with genetic and biochemical assays, identified a novel transcription factor termed HgtR that acts as a repressor for gltA. Further analysis revealed that HgtR is a global regulator for genes involved in biosynthesis and energy generation in Geobacter species. The hgtR gene was essential for growth with hydrogen, during which hgtR expression was induced. These findings provide important new insights into the mechanisms by which Geobacter species regulate their central metabolism under different environmental conditions.
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Affiliation(s)
- Toshiyuki Ueki
- Department of Microbiology, University of Massachusetts Amherst, North, Amherst, MA 01003-9298, USA.
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Schuetz B, Schicklberger M, Kuermann J, Spormann AM, Gescher J. Periplasmic electron transfer via the c-type cytochromes MtrA and FccA of Shewanella oneidensis MR-1. Appl Environ Microbiol 2009; 75:7789-96. [PMID: 19837833 DOI: 10.1128/AEM.01834-09] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dissimilatory microbial reduction of insoluble Fe(III) oxides is a geochemically and ecologically important process which involves the transfer of cellular, respiratory electrons from the cytoplasmic membrane to insoluble, extracellular, mineral-phase electron acceptors. In this paper evidence is provided for the function of the periplasmic fumarate reductase FccA and the decaheme c-type cytochrome MtrA in periplasmic electron transfer reactions in the gammaproteobacterium Shewanella oneidensis. Both proteins are abundant in the periplasm of ferric citrate-reducing S. oneidensis cells. In vitro fumarate reductase FccA and c-type cytochrome MtrA were reduced by the cytoplasmic membrane-bound protein CymA. Electron transfer between CymA and MtrA was 1.4-fold faster than the CymA-catalyzed reduction of FccA. Further experiments showing a bidirectional electron transfer between FccA and MtrA provided evidence for an electron transfer network in the periplasmic space of S. oneidensis. Hence, FccA could function in both the electron transport to fumarate and via MtrA to mineral-phase Fe(III). Growth experiments with a DeltafccA deletion mutant suggest a role of FccA as a transient electron storage protein.
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Leang C, Krushkal J, Ueki T, Puljic M, Sun J, Juárez K, Núñez C, Reguera G, DiDonato R, Postier B, Adkins RM, Lovley DR. Genome-wide analysis of the RpoN regulon in Geobacter sulfurreducens. BMC Genomics 2009; 10:331. [PMID: 19624843 DOI: 10.1186/1471-2164-10-331] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 07/22/2009] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The role of the RNA polymerase sigma factor RpoN in regulation of gene expression in Geobacter sulfurreducens was investigated to better understand transcriptional regulatory networks as part of an effort to develop regulatory modules for genome-scale in silico models, which can predict the physiological responses of Geobacter species during groundwater bioremediation or electricity production. RESULTS An rpoN deletion mutant could not be obtained under all conditions tested. In order to investigate the regulon of the G. sulfurreducens RpoN, an RpoN over-expression strain was made in which an extra copy of the rpoN gene was under the control of a taclac promoter. Combining both the microarray transcriptome analysis and the computational prediction revealed that the G. sulfurreducens RpoN controls genes involved in a wide range of cellular functions. Most importantly, RpoN controls the expression of the dcuB gene encoding the fumarate/succinate exchanger, which is essential for cell growth with fumarate as the terminal electron acceptor in G. sulfurreducens. RpoN also controls genes, which encode enzymes for both pathways of ammonia assimilation that is predicted to be essential under all growth conditions in G. sulfurreducens. Other genes that were identified as part of the RpoN regulon using either the computational prediction or the microarray transcriptome analysis included genes involved in flagella biosynthesis, pili biosynthesis and genes involved in central metabolism enzymes and cytochromes involved in extracellular electron transfer to Fe(III), which are known to be important for growth in subsurface environment or electricity production in microbial fuel cells. The consensus sequence for the predicted RpoN-regulated promoter elements is TTGGCACGGTTTTTGCT. CONCLUSION The G. sulfurreducens RpoN is an essential sigma factor and a global regulator involved in a complex transcriptional network controlling a variety of cellular processes.
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Weingarten RA, Taveirne ME, Olson JW. The dual-functioning fumarate reductase is the sole succinate:quinone reductase in Campylobacter jejuni and is required for full host colonization. J Bacteriol 2009; 191:5293-300. [PMID: 19525346 DOI: 10.1128/JB.00166-09] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Campylobacter jejuni encodes all the enzymes necessary for a complete oxidative tricarboxylic acid (TCA) cycle. Because of its inability to utilize glucose, C. jejuni relies exclusively on amino acids as the source of reduced carbon, and they are incorporated into central carbon metabolism. The oxidation of succinate to fumarate is a key step in the oxidative TCA cycle. C. jejuni encodes enzymes annotated as a fumarate reductase (Cj0408 to Cj0410) and a succinate dehydrogenase (Cj0437 to Cj0439). Null alleles in the genes encoding each enzyme were constructed. Both enzymes contributed to the total fumarate reductase activity in vitro. The frdA::cat(+) strain was completely deficient in succinate dehydrogenase activity in vitro and was unable to perform whole-cell succinate-dependent respiration. The sdhA::cat(+) strain exhibited wild-type levels of succinate dehydrogenase activity both in vivo and in vitro. These data indicate that Frd is the only succinate dehydrogenase in C. jejuni and that the protein annotated as a succinate dehydrogenase has been misannotated. The frdA::cat(+) strain was also unable to grow with the characteristic wild-type biphasic growth pattern and exhibited only the first growth phase, which is marked by the consumption of aspartate, serine, and associated organic acids. Substrates consumed in the second growth phase (glutamate, proline, and associated organic acids) were not catabolized by the the frdA::cat(+) strain, indicating that the oxidation of succinate is a crucial step in metabolism of these substrates. Chicken colonization trials confirmed the in vivo importance of succinate oxidation, as the frdA::cat(+) strain colonized chickens at significantly lower levels than the wild type, while the sdhA::cat(+) strain colonized chickens at wild-type levels.
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Aklujkar M, Krushkal J, DiBartolo G, Lapidus A, Land ML, Lovley DR. The genome sequence of Geobacter metallireducens: features of metabolism, physiology and regulation common and dissimilar to Geobacter sulfurreducens. BMC Microbiol 2009; 9:109. [PMID: 19473543 PMCID: PMC2700814 DOI: 10.1186/1471-2180-9-109] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 05/27/2009] [Indexed: 12/12/2022] Open
Abstract
Background The genome sequence of Geobacter metallireducens is the second to be completed from the metal-respiring genus Geobacter, and is compared in this report to that of Geobacter sulfurreducens in order to understand their metabolic, physiological and regulatory similarities and differences. Results The experimentally observed greater metabolic versatility of G. metallireducens versus G. sulfurreducens is borne out by the presence of more numerous genes for metabolism of organic acids including acetate, propionate, and pyruvate. Although G. metallireducens lacks a dicarboxylic acid transporter, it has acquired a second putative succinate dehydrogenase/fumarate reductase complex, suggesting that respiration of fumarate was important until recently in its evolutionary history. Vestiges of the molybdate (ModE) regulon of G. sulfurreducens can be detected in G. metallireducens, which has lost the global regulatory protein ModE but retained some putative ModE-binding sites and multiplied certain genes of molybdenum cofactor biosynthesis. Several enzymes of amino acid metabolism are of different origin in the two species, but significant patterns of gene organization are conserved. Whereas most Geobacteraceae are predicted to obtain biosynthetic reducing equivalents from electron transfer pathways via a ferredoxin oxidoreductase, G. metallireducens can derive them from the oxidative pentose phosphate pathway. In addition to the evidence of greater metabolic versatility, the G. metallireducens genome is also remarkable for the abundance of multicopy nucleotide sequences found in intergenic regions and even within genes. Conclusion The genomic evidence suggests that metabolism, physiology and regulation of gene expression in G. metallireducens may be dramatically different from other Geobacteraceae.
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Affiliation(s)
- Muktak Aklujkar
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA, USA.
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Nevin KP, Kim BC, Glaven RH, Johnson JP, Woodard TL, Methé BA, Didonato RJ, Covalla SF, Franks AE, Liu A, Lovley DR. Anode biofilm transcriptomics reveals outer surface components essential for high density current production in Geobacter sulfurreducens fuel cells. PLoS One 2009; 4:e5628. [PMID: 19461962 PMCID: PMC2680965 DOI: 10.1371/journal.pone.0005628] [Citation(s) in RCA: 326] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 04/10/2009] [Indexed: 11/19/2022] Open
Abstract
The mechanisms by which Geobacter sulfurreducens transfers electrons through relatively thick (>50 microm) biofilms to electrodes acting as a sole electron acceptor were investigated. Biofilms of Geobacter sulfurreducens were grown either in flow-through systems with graphite anodes as the electron acceptor or on the same graphite surface, but with fumarate as the sole electron acceptor. Fumarate-grown biofilms were not immediately capable of significant current production, suggesting substantial physiological differences from current-producing biofilms. Microarray analysis revealed 13 genes in current-harvesting biofilms that had significantly higher transcript levels. The greatest increases were for pilA, the gene immediately downstream of pilA, and the genes for two outer c-type membrane cytochromes, OmcB and OmcZ. Down-regulated genes included the genes for the outer-membrane c-type cytochromes, OmcS and OmcT. Results of quantitative RT-PCR of gene transcript levels during biofilm growth were consistent with microarray results. OmcZ and the outer-surface c-type cytochrome, OmcE, were more abundant and OmcS was less abundant in current-harvesting cells. Strains in which pilA, the gene immediately downstream from pilA, omcB, omcS, omcE, or omcZ was deleted demonstrated that only deletion of pilA or omcZ severely inhibited current production and biofilm formation in current-harvesting mode. In contrast, these gene deletions had no impact on biofilm formation on graphite surfaces when fumarate served as the electron acceptor. These results suggest that biofilms grown harvesting current are specifically poised for electron transfer to electrodes and that, in addition to pili, OmcZ is a key component in electron transfer through differentiated G. sulfurreducens biofilms to electrodes.
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Affiliation(s)
- Kelly P Nevin
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA.
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Butler JE, Young ND, Lovley DR. Evolution from a respiratory ancestor to fill syntrophic and fermentative niches: comparative fenomics of six Geobacteraceae species. BMC Genomics 2009; 10:103. [PMID: 19284579 PMCID: PMC2669807 DOI: 10.1186/1471-2164-10-103] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 03/11/2009] [Indexed: 11/26/2022] Open
Abstract
Background The anaerobic degradation of organic matter in natural environments, and the biotechnical use of anaerobes in energy production and remediation of subsurface environments, both require the cooperative activity of a diversity of microorganisms in different metabolic niches. The Geobacteraceae family contains members with three important anaerobic metabolisms: fermentation, syntrophic degradation of fermentation intermediates, and anaerobic respiration. Results In order to learn more about the evolution of anaerobic microbial communities, the genome sequences of six Geobacteraceae species were analyzed. The results indicate that the last common Geobacteraceae ancestor contained sufficient genes for anaerobic respiration, completely oxidizing organic compounds with the reduction of external electron acceptors, features that are still retained in modern Geobacter and Desulfuromonas species. Evolution of specialization for fermentative growth arose twice, via distinct lateral gene transfer events, in Pelobacter carbinolicus and Pelobacter propionicus. Furthermore, P. carbinolicus gained hydrogenase genes and genes for ferredoxin reduction that appear to permit syntrophic growth via hydrogen production. The gain of new physiological capabilities in the Pelobacter species were accompanied by the loss of several key genes necessary for the complete oxidation of organic compounds and the genes for the c-type cytochromes required for extracellular electron transfer. Conclusion The results suggest that Pelobacter species evolved parallel strategies to enhance their ability to compete in environments in which electron acceptors for anaerobic respiration were limiting. More generally, these results demonstrate how relatively few gene changes can dramatically transform metabolic capabilities and expand the range of environments in which microorganisms can compete.
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Affiliation(s)
- Jessica E Butler
- Department of Microbiology, 203 Morrill Science Center IVN, University of Massachusetts, Amherst, MA 01003, USA.
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Sun J, Sayyar B, Butler JE, Pharkya P, Fahland TR, Famili I, Schilling CH, Lovley DR, Mahadevan R. Genome-scale constraint-based modeling of Geobacter metallireducens. BMC Syst Biol 2009; 3:15. [PMID: 19175927 PMCID: PMC2640342 DOI: 10.1186/1752-0509-3-15] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Accepted: 01/28/2009] [Indexed: 11/17/2022]
Abstract
Background Geobacter metallireducens was the first organism that can be grown in pure culture to completely oxidize organic compounds with Fe(III) oxide serving as electron acceptor. Geobacter species, including G. sulfurreducens and G. metallireducens, are used for bioremediation and electricity generation from waste organic matter and renewable biomass. The constraint-based modeling approach enables the development of genome-scale in silico models that can predict the behavior of complex biological systems and their responses to the environments. Such a modeling approach was applied to provide physiological and ecological insights on the metabolism of G. metallireducens. Results The genome-scale metabolic model of G. metallireducens was constructed to include 747 genes and 697 reactions. Compared to the G. sulfurreducens model, the G. metallireducens metabolic model contains 118 unique reactions that reflect many of G. metallireducens' specific metabolic capabilities. Detailed examination of the G. metallireducens model suggests that its central metabolism contains several energy-inefficient reactions that are not present in the G. sulfurreducens model. Experimental biomass yield of G. metallireducens growing on pyruvate was lower than the predicted optimal biomass yield. Microarray data of G. metallireducens growing with benzoate and acetate indicated that genes encoding these energy-inefficient reactions were up-regulated by benzoate. These results suggested that the energy-inefficient reactions were likely turned off during G. metallireducens growth with acetate for optimal biomass yield, but were up-regulated during growth with complex electron donors such as benzoate for rapid energy generation. Furthermore, several computational modeling approaches were applied to accelerate G. metallireducens research. For example, growth of G. metallireducens with different electron donors and electron acceptors were studied using the genome-scale metabolic model, which provided a fast and cost-effective way to understand the metabolism of G. metallireducens. Conclusion We have developed a genome-scale metabolic model for G. metallireducens that features both metabolic similarities and differences to the published model for its close relative, G. sulfurreducens. Together these metabolic models provide an important resource for improving strategies on bioremediation and bioenergy generation.
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Affiliation(s)
- Jun Sun
- Genomatica Inc, San Diego, CA, USA.
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Xin Y, Lu YK, Fromme R, Fromme P, Blankenship RE. Purification, characterization and crystallization of menaquinol:fumarate oxidoreductase from the green filamentous photosynthetic bacterium Chloroflexus aurantiacus. Biochim Biophys Acta 2008; 1787:86-96. [PMID: 19103151 DOI: 10.1016/j.bbabio.2008.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Revised: 11/20/2008] [Accepted: 11/21/2008] [Indexed: 11/17/2022]
Abstract
The integral membrane protein complex, menaquinol:fumarate oxidoreductase (mQFR) has been purified, identified and characterized from the thermophilic green filamentous anoxygenic photosynthetic bacterium Chloroflexus aurantiacus. The complex is composed of three subunits: a 74 kDa flavoprotein that contains a covalently bound flavin adenine dinucleotide, a 28 kDa iron-sulfur cluster-containing polypeptide, and a 27 kDa transmembrane polypeptide, which is also the binding site of two b-type hemes and two menaquinones. The purified complex has an apparent molecular mass of 260 kDa by blue-native PAGE, which is indicative of a native homodimeric form. The isolated complex is active in vitro in both fumarate reduction and succinate oxidation. It has been analyzed by visible absorption, redox titration, chemical analysis and EPR spectroscopy. In addition, phylogenetic analysis shows that the QFR of both C. aurantiacus and Chlorobium tepidum are most closely related to those found in the delta-proteobacteria. The purified enzyme was crystallized and X-ray diffraction data obtained up to 3.2 A resolution.
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Affiliation(s)
- Yueyong Xin
- Departments of Biology and Chemistry, Washington University, Campus Box 1137, One Brooking Drive, St. Louis, MO 63130, USA
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