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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] [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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2
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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] [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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Zhang X, Joyce GH, Leu AO, Zhao J, Rabiee H, Virdis B, Tyson GW, Yuan Z, McIlroy SJ, Hu S. Multi-heme cytochrome-mediated extracellular electron transfer by the anaerobic methanotroph 'Candidatus Methanoperedens nitroreducens'. Nat Commun 2023; 14:6118. [PMID: 37777538 PMCID: PMC10542353 DOI: 10.1038/s41467-023-41847-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 09/18/2023] [Indexed: 10/02/2023] Open
Abstract
Anaerobic methanotrophic archaea (ANME) carry out anaerobic oxidation of methane, thus playing a crucial role in the methane cycle. Previous genomic evidence indicates that multi-heme c-type cytochromes (MHCs) may facilitate the extracellular electron transfer (EET) from ANME to different electron sinks. Here, we provide experimental evidence supporting cytochrome-mediated EET for the reduction of metals and electrodes by 'Candidatus Methanoperedens nitroreducens', an ANME acclimated to nitrate reduction. Ferrous iron-targeted fluorescent assays, metatranscriptomics, and single-cell imaging suggest that 'Ca. M. nitroreducens' uses surface-localized redox-active cytochromes for metal reduction. Electrochemical and Raman spectroscopic analyses also support the involvement of c-type cytochrome-mediated EET for electrode reduction. Furthermore, several genes encoding menaquinone cytochrome type-c oxidoreductases and extracellular MHCs are differentially expressed when different electron acceptors are used.
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Affiliation(s)
- Xueqin Zhang
- Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, University of Queensland, Brisbane, Australia
| | - Georgina H Joyce
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, Australia
| | - Andy O Leu
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, Australia
| | - Jing Zhao
- Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, University of Queensland, Brisbane, Australia
- Ecological Engineering of Mine Wastes, Sustainable Minerals Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Hesamoddin Rabiee
- Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, University of Queensland, Brisbane, Australia
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD, Australia
- Centre for Future Materials, University of Southern Queensland, Springfield, QLD, Australia
| | - Bernardino Virdis
- Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, University of Queensland, Brisbane, Australia
| | - Gene W Tyson
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, Australia
| | - Zhiguo Yuan
- Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, University of Queensland, Brisbane, Australia
- School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China
| | - Simon J McIlroy
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, Australia
| | - Shihu Hu
- Australian Centre for Water and Environmental Biotechnology (ACWEB), Faculty of Engineering, Architecture and Information Technology, University of Queensland, Brisbane, Australia.
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Liu Y, Zhao Q, Liao C, Tian L, Yan X, Li N, Wang X. Anaerobic bioreduction of elemental sulfur improves bioavailability of Fe (III) oxides for bioremediation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 858:159794. [PMID: 36374751 DOI: 10.1016/j.scitotenv.2022.159794] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 10/04/2022] [Accepted: 10/24/2022] [Indexed: 06/16/2023]
Abstract
Fe(III) oxides are ubiquitous electron acceptors for anaerobic bioremediation, although their bioavailability was limited due to the passivation of secondary mineralization products. Here we found the solid S0 can be added to improve their bioavailability. Using lepidocrocite (γ-FeOOH), acetate and Geobacter sulfurreducens PCA as representatives of Fe(III) oxides, intermediate of pollutant degradation and microbes, a 6 times higher amount of FeOOH reduction in the presence of S0 was observed with a time needed for S0 reduction shortened by half. The bioreduction of S0 activated the reduction of FeOOH, while the product (conductive FeS) may have bridged electron transfer across the cell membrane and periplasm. The proportion of excessive Fe(II) produced from Fe(III) was quantified as a direct bioreduction (26 %), with an abiotic FeOOH reduction to FeS (20 %) and an FeS-conducted FeOOH bioreduction (54 %), which highlight the key role of gradually formed FeS from S0 in the bioreduction of FeOOH. Our results showed that S0 can be an effective additive for the bioremediation of environments with abundant Fe(III) oxides, which has broader implications for elemental biogeochemical cycling.
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Affiliation(s)
- Ying Liu
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Qian Zhao
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Chengmei Liao
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Lili Tian
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Xuejun Yan
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Nan Li
- School of Environmental Science and Engineering, Tianjin University, No. 135 Yaguan Road, Jinnan District, Tianjin 300350, China
| | - Xin Wang
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China.
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Singh KS, Paul D, Gupta A, Dhotre D, Klawonn F, Shouche Y. Indian sewage microbiome has unique community characteristics and potential for population-level disease predictions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 858:160178. [PMID: 36379333 DOI: 10.1016/j.scitotenv.2022.160178] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 10/31/2022] [Accepted: 11/10/2022] [Indexed: 06/16/2023]
Abstract
Sewage wastewater pollutes water and poses a public health issue but it could also prove useful in certain research domains. Sewage is a complex niche relevant for research concerning 'one-health', human health, pollution and antibiotic resistance. Indian gut microbiome is also understudied due to sampling constraints and sewage could be used to explore it. Ostensibly, Indian sewage needs to be studied and here, we performed a cross-sectional pan-India sewage sampling to generate the first comprehensive Indian sewage microbiome. Indian sewage showed predominance of Burkholderiaceae, Rhodocyclaceae, Veillonellaceae, Prevotellaceae, etc. and has high representation of gut microbes. The identified gut microbes have overrepresentation of Veillonellaceae, Rikenellaceae, Streptococcaceae, and Bacillaceae. Imputed metagenomics of sewage microbiome indicated dominance of transport, motility, peptidases, amino acid metabolism, and antibiotic resistance genes. Microbiome-disease associations drawn using simple decision tree and random forest analysis identified specific microbes as potential predictors of diabetes and obesity in a city. Altogether, we generated the first Indian sewage microbiome and our non-invasive, high-throughput workflow could be emulated for future research, wastewater-based epidemiology and designing policies concerning public health.
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Affiliation(s)
- Kumar Siddharth Singh
- National Centre for Microbial Resource - National Centre for Cell Science, Pune, India; Institute for Microbiology, Leibniz University, Hannover, Germany
| | - Dhiraj Paul
- National Centre for Microbial Resource - National Centre for Cell Science, Pune, India
| | - Abhishek Gupta
- National Centre for Microbial Resource - National Centre for Cell Science, Pune, India
| | - Dhiraj Dhotre
- National Centre for Microbial Resource - National Centre for Cell Science, Pune, India
| | - Frank Klawonn
- Biostatistics, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Yogesh Shouche
- National Centre for Microbial Resource - National Centre for Cell Science, Pune, India; Azim Premji University, Bengaluru, India.
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6
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Gutensohn M, Schaefer JK, Maas TJ, Skyllberg U, Björn E. Metabolic turnover of cysteine-related thiol compounds at environmentally relevant concentrations by Geobacter sulfurreducens. Front Microbiol 2023; 13:1085214. [PMID: 36713222 PMCID: PMC9874932 DOI: 10.3389/fmicb.2022.1085214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 12/22/2022] [Indexed: 01/12/2023] Open
Abstract
Low-molecular-mass (LMM) thiol compounds are known to be important for many biological processes in various organisms but LMM thiols are understudied in anaerobic bacteria. In this work, we examined the production and turnover of nanomolar concentrations of LMM thiols with a chemical structure related to cysteine by the model iron-reducing bacterium Geobacter sulfurreducens. Our results show that G. sulfurreducens tightly controls the production, excretion and intracellular concentration of thiols depending on cellular growth state and external conditions. The production and cellular export of endogenous cysteine was coupled to the extracellular supply of Fe(II), suggesting that cysteine excretion may play a role in cellular trafficking to iron proteins. Addition of excess exogenous cysteine resulted in a rapid and extensive conversion of cysteine to penicillamine by the cells. Experiments with added isotopically labeled cysteine confirmed that penicillamine was formed by a dimethylation of the C-3 atom of cysteine and not via indirect metabolic responses to cysteine exposure. This is the first report of de novo metabolic synthesis of this compound. Penicillamine formation increased with external exposure to cysteine but the compound did not accumulate intracellularly, which may suggest that it is part of G. sulfurreducens' metabolic strategy to maintain cysteine homeostasis. Our findings highlight and expand on processes mediating homeostasis of cysteine-like LMM thiols in strict anaerobic bacteria. The formation of penicillamine is particularly noteworthy and this compound warrants more attention in microbial metabolism studies.
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Affiliation(s)
| | - Jeffra K. Schaefer
- Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, United States
| | - Torben J. Maas
- Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstraße, Münster, Germany
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, Umeå, Sweden,*Correspondence: Erik Björn, ✉
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7
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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] [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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8
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Huang TY, Lim HL. Electrogenic Staphylococcus warneri in lactate-rich skin. Biochem Biophys Res Commun 2022; 618:67-72. [PMID: 35716597 DOI: 10.1016/j.bbrc.2022.06.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 06/01/2022] [Accepted: 06/08/2022] [Indexed: 11/02/2022]
Abstract
The electrogenicity of environmental bacteria has been thoroughly explored and has been known to have the unique capability of decomposing hazardous chemicals for environmental remediation. However, electrogenic bacteria in human skin in regards to their electrical properties and locations have not yet been determined. Here, electrodermal activities and metabolite compositions at different locations of arm skin were assessed. Compared to the uppermost part of arm, we found that the forearm elicited high electrodermal activity and carried abundant lactate and alpha-ketoglutarate, two components commonly present in sweat. Upon culturing bacteria from the forearm, an iron-resistant strain of Staphylococcus warneri (S. warneri) was identified through 16S ribosomal RNA sequencing. Voltage changes induced by S. warneri in the presence of glucose were detected by two voltmeters of different electrode materials, demonstrating the electrogenicity of skin bacteria. Furthermore, we discovered that S. warneri has the ability to metabolize lactate to generate electricity. The results of this study reveal changes in skin conductance caused by bacterial electricity that are mediated by skin endogenous molecules and may provide a novel method of monitoring environmental skin insults.
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Aguinaga OE, White KN, Dean AP, Pittman JK. Addition of organic acids to acid mine drainage polluted wetland sediment leads to microbial community structure and functional changes and improved water quality. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 290:118064. [PMID: 34481302 DOI: 10.1016/j.envpol.2021.118064] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/24/2021] [Accepted: 08/26/2021] [Indexed: 06/13/2023]
Abstract
Acid mine drainage (AMD) is a serious environmental problem worldwide that requires efficient and sustainable remediation technologies including the use of biological mechanisms. A key challenge for AMD bioremediation is to provide optimal conditions for microbial-mediated immobilisation of trace metals. Although organic carbon and oxygen can enhance treatment efficiency, the effect on microbial communities is unclear. In this study, surface sediments from a natural wetland with proven efficiency for AMD bioremediation were artificially exposed to oxygen (by aeration) and/or organic carbon (in the form of mixed organic acids) and incubated under laboratory conditions. In addition to measuring changes in water chemistry, a metagenomics approach was used to determine changes in sediment bacterial, archaeal and fungal community structure, and functional gene abundance. The addition of organic carbon produced major changes in the abundance of microorganisms related to iron and sulfur metabolism (including Geobacter and Pelobacter) and increased levels of particulate metals via sulfate reduction. Aeration resulted in an increase in Sideroxydans abundance but no significant changes in metal chemistry were observed. The study concludes that the utilisation of organic carbon by microorganisms is more important for achieving efficient AMD treatment than the availability of oxygen, yet the combination of oxygen with organic carbon addition did not inhibit the improvements to water quality.
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Affiliation(s)
- Oscar E Aguinaga
- Department of Earth and Environmental Sciences, School of Natural Sciences, Faculty of Science and Engineering, The University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK; Departamento de Ingeniería, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Keith N White
- Department of Earth and Environmental Sciences, School of Natural Sciences, Faculty of Science and Engineering, The University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
| | - Andrew P Dean
- Department of Natural Sciences, Faculty of Science and Engineering, Manchester Metropolitan University, Oxford Road, Manchester, M1 5GD, UK
| | - Jon K Pittman
- Department of Earth and Environmental Sciences, School of Natural Sciences, Faculty of Science and Engineering, The University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK.
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Marcos-Torres FJ, Maurer D, Juniar L, Griese JJ. The bacterial iron sensor IdeR recognizes its DNA targets by indirect readout. Nucleic Acids Res 2021; 49:10120-10135. [PMID: 34417623 PMCID: PMC8464063 DOI: 10.1093/nar/gkab711] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/19/2021] [Accepted: 08/02/2021] [Indexed: 01/11/2023] Open
Abstract
The iron-dependent regulator IdeR is the main transcriptional regulator controlling iron homeostasis genes in Actinobacteria, including species from the Corynebacterium, Mycobacterium and Streptomyces genera, as well as the erythromycin-producing bacterium Saccharopolyspora erythraea. Despite being a well-studied transcription factor since the identification of the Diphtheria toxin repressor DtxR three decades ago, the details of how IdeR proteins recognize their highly conserved 19-bp DNA target remain to be elucidated. IdeR makes few direct contacts with DNA bases in its target sequence, and we show here that these contacts are not required for target recognition. The results of our structural and mutational studies support a model wherein IdeR mainly uses an indirect readout mechanism, identifying its targets via the sequence-dependent DNA backbone structure rather than through specific contacts with the DNA bases. Furthermore, we show that IdeR efficiently recognizes a shorter palindromic sequence corresponding to a half binding site as compared to the full 19-bp target previously reported, expanding the number of potential target genes controlled by IdeR proteins.
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Affiliation(s)
| | - Dirk Maurer
- Department of Cell and Molecular Biology, Uppsala University, SE-751 24 Uppsala, Sweden
| | - Linda Juniar
- Department of Cell and Molecular Biology, Uppsala University, SE-751 24 Uppsala, Sweden
| | - Julia J Griese
- Department of Cell and Molecular Biology, Uppsala University, SE-751 24 Uppsala, Sweden
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11
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Madeira CL, Menezes O, Park D, Jog KV, Hatt JK, Gavazza S, Krzmarzick MJ, Sierra-Alvarez R, Spain JC, Konstantinidis KT, Field JA. Bacteria Make a Living Breathing the Nitroheterocyclic Insensitive Munitions Compound 3-Nitro-1,2,4-triazol-5-one (NTO). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:5806-5814. [PMID: 33835790 DOI: 10.1021/acs.est.0c07161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The nitroheterocyclic 3-nitro-1,2,4-triazol-5-one (NTO) is an ingredient of insensitive explosives increasingly used by the military, becoming an emergent environmental pollutant. Cometabolic biotransformation of NTO occurs in mixed microbial cultures in soils and sludges with excess electron-donating substrates. Herein, we present the unusual energy-yielding metabolic process of NTO respiration, in which the NTO reduction to 3-amino-1,2,4-triazol-5-one (ATO) is linked to the anoxic acetate oxidation to CO2 by a culture enriched from municipal anaerobic digester sludge. Cell growth was observed simultaneously with NTO reduction, whereas the culture was unable to grow in the presence of acetate only. Extremely low concentrations (0.06 mg L-1) of the uncoupler carbonyl cyanide m-chlorophenyl hydrazone inhibited NTO reduction, indicating that the process was linked to respiration. The ultimate evidence of NTO respiration was adenosine triphosphate production due to simultaneous exposure to NTO and acetate. Metagenome sequencing revealed that the main microorganisms (and relative abundances) were Geobacter anodireducens (89.3%) and Thauera sp. (5.5%). This study is the first description of a nitroheterocyclic compound being reduced by anaerobic respiration, shedding light on creative microbial processes that enable bacteria to make a living reducing NTO.
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Affiliation(s)
- Camila L Madeira
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721-0011, United States
| | - Osmar Menezes
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721-0011, United States
- Laboratório de Saneamento Ambiental, Departamento de Engenharia Civil e Ambiental, Universidade Federal de Pernambuco, Recife, Pernambuco 50740-530, Brazil
| | - Doyoung Park
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0355, United States
| | - Kalyani V Jog
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721-0011, United States
| | - Janet K Hatt
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0355, United States
| | - Savia Gavazza
- Laboratório de Saneamento Ambiental, Departamento de Engenharia Civil e Ambiental, Universidade Federal de Pernambuco, Recife, Pernambuco 50740-530, Brazil
| | - Mark J Krzmarzick
- School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Reyes Sierra-Alvarez
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721-0011, United States
| | - Jim C Spain
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0355, United States
- Center for Environmental Diagnostics & Bioremediation, University of West Florida, Pensacola, Florida 32514, United States
| | - Konstantinos T Konstantinidis
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0355, United States
| | - Jim A Field
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721-0011, United States
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12
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Xu Y, Yang S, You G, Hou J. Antibiotic resistance genes attenuation in anaerobic microorganisms during iron uptake from zero valent iron: An iron-dependent form of homeostasis and roles as regulators. WATER RESEARCH 2021; 195:116979. [PMID: 33690012 DOI: 10.1016/j.watres.2021.116979] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 02/17/2021] [Accepted: 02/24/2021] [Indexed: 06/12/2023]
Abstract
Zero valent iron (ZVI) has been previously documented to attenuate the propagation of antibiotic resistance genes (ARGs) in microbes, while how ZVI affects the evolution of ARGs remains unclear. Herein, we investigated the influences of ZVI on ARGs dissemination in anaerobic bioreactor treating oxytetracycline (tet) containing wastewater, by deciphering the roles of iron homeostasis and regulatory effects. A net reduction of tet gene targets ranging from 0.75 to 1.88 and 0.67 to 2.08 log unit in intracellular and extracellular DNA was achieved at the optimal dosage of 5 g/L ZVI, whereas 20 g/L ZVI made no effects on ARGs reduction. The reduced ARGs abundance by ZVI was directly related to the inhibited horizontal transfer of ARGs and decreased proliferation of resistant strains (mainly Paludibacter and WCHB1-32). The potential mechanisms included the increased antioxidant capacity, the depressed efflux pump system and the weakened energy driving force by Fur regulon in microbes (especially for Cloacibacterium and Dechloromonas). The negligible influence of 20 g/L ZVI on ARGs reduction was ascribed to the iron-catalyzed oxidative damage and reduced physiological activity. This study firstly illustrated the potential relationships among activation of iron uptake regulator leading to protection against oxidative stress, alternation of physiological metabolisms and reduction of ARGs dissemination. This work extents our understanding about the priority of ZVI in mitigating ARGs proliferation and sheds light on its potential application in wastewater treatment plants.
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Affiliation(s)
- Yi Xu
- College of Agricultural Engineering, Hohai University, Nanjing, 210098, PR China; Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, 1 Xikang Road, Nanjing 210098, PR China
| | - Shihong Yang
- College of Agricultural Engineering, Hohai University, Nanjing, 210098, PR China
| | - Guoxiang You
- Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, 1 Xikang Road, Nanjing 210098, PR China
| | - Jun Hou
- Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, 1 Xikang Road, Nanjing 210098, PR China.
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13
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Bradley JM, Svistunenko DA, Wilson MT, Hemmings AM, Moore GR, Le Brun NE. Bacterial iron detoxification at the molecular level. J Biol Chem 2021; 295:17602-17623. [PMID: 33454001 PMCID: PMC7762939 DOI: 10.1074/jbc.rev120.007746] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 10/07/2020] [Indexed: 01/18/2023] Open
Abstract
Iron is an essential micronutrient, and, in the case of bacteria, its availability is commonly a growth-limiting factor. However, correct functioning of cells requires that the labile pool of chelatable "free" iron be tightly regulated. Correct metalation of proteins requiring iron as a cofactor demands that such a readily accessible source of iron exist, but overaccumulation results in an oxidative burden that, if unchecked, would lead to cell death. The toxicity of iron stems from its potential to catalyze formation of reactive oxygen species that, in addition to causing damage to biological molecules, can also lead to the formation of reactive nitrogen species. To avoid iron-mediated oxidative stress, bacteria utilize iron-dependent global regulators to sense the iron status of the cell and regulate the expression of proteins involved in the acquisition, storage, and efflux of iron accordingly. Here, we survey the current understanding of the structure and mechanism of the important members of each of these classes of protein. Diversity in the details of iron homeostasis mechanisms reflect the differing nutritional stresses resulting from the wide variety of ecological niches that bacteria inhabit. However, in this review, we seek to highlight the similarities of iron homeostasis between different bacteria, while acknowledging important variations. In this way, we hope to illustrate how bacteria have evolved common approaches to overcome the dual problems of the insolubility and potential toxicity of iron.
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Affiliation(s)
- Justin M Bradley
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom.
| | | | - Michael T Wilson
- School of Life Sciences, University of Essex, Colchester, United Kingdom
| | - Andrew M Hemmings
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom; Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Geoffrey R Moore
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich, United Kingdom.
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14
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Dulay H, Tabares M, Kashefi K, Reguera G. Cobalt Resistance via Detoxification and Mineralization in the Iron-Reducing Bacterium Geobacter sulfurreducens. Front Microbiol 2020; 11:600463. [PMID: 33324382 PMCID: PMC7726332 DOI: 10.3389/fmicb.2020.600463] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 11/03/2020] [Indexed: 12/18/2022] Open
Abstract
Bacteria in the genus Geobacter thrive in iron- and manganese-rich environments where the divalent cobalt cation (CoII) accumulates to potentially toxic concentrations. Consistent with selective pressure from environmental exposure, the model laboratory representative Geobacter sulfurreducens grew with CoCl2 concentrations (1 mM) typically used to enrich for metal-resistant bacteria from contaminated sites. We reconstructed from genomic data canonical pathways for CoII import and assimilation into cofactors (cobamides) that support the growth of numerous syntrophic partners. We also identified several metal efflux pumps, including one that was specifically upregulated by CoII. Cells acclimated to metal stress by downregulating non-essential proteins with metals and thiol groups that CoII preferentially targets. They also activated sensory and regulatory proteins involved in detoxification as well as pathways for protein and DNA repair. In addition, G. sulfurreducens upregulated respiratory chains that could have contributed to the reductive mineralization of the metal on the cell surface. Transcriptomic evidence also revealed pathways for cell envelope modification that increased metal resistance and promoted cell-cell aggregation and biofilm formation in stationary phase. These complex adaptive responses confer on Geobacter a competitive advantage for growth in metal-rich environments that are essential to the sustainability of cobamide-dependent microbiomes and the sequestration of the metal in hitherto unknown biomineralization reactions.
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Affiliation(s)
- Hunter Dulay
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, United States
| | - Marcela Tabares
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, United States
| | - Kazem Kashefi
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, United States
| | - Gemma Reguera
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, United States
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15
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Adediran GA, Liem-Nguyen V, Song Y, Schaefer JK, Skyllberg U, Björn E. Microbial Biosynthesis of Thiol Compounds: Implications for Speciation, Cellular Uptake, and Methylation of Hg(II). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8187-8196. [PMID: 31257868 DOI: 10.1021/acs.est.9b01502] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Cellular uptake of inorganic divalent mercury (Hg(II)) is a key step in microbial formation of neurotoxic methylmercury (MeHg), but the mechanisms remain largely unidentified. We show that the iron reducing bacterium Geobacter sulfurreducens produces and exports appreciable amounts of low molecular mass thiol (LMM-RSH) compounds reaching concentrations of about 100 nM in the assay medium. These compounds largely control the chemical speciation and bioavailability of Hg(II) by the formation of Hg(LMM-RS)2 complexes (primarily with cysteine) in assays without added thiols. By characterizing these effects, we show that the thermodynamic stability of Hg(II)-complexes is a principal controlling factor for Hg(II) methylation by this bacterium such that less stable complexes with mixed ligation involving LMM-RSH, OH-, and Cl- are methylated at higher rates than the more stable Hg(LMM-RS)2 complexes. The Hg(II) methylation rate across different Hg(LMM-RS)2 compounds is also influenced by the chemical structure of the complexes. In contrast to the current perception of microbial uptake of Hg, our results adhere to generalized theories for metal biouptake based on metal complexation with cell surface ligands and refine the mechanistic understanding of Hg(II) availability for microbial methylation.
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Affiliation(s)
| | - Van Liem-Nguyen
- Department of Chemistry , Umeå University , SE- 90187 Umeå , Sweden
- School of Science and Technology , Örebro University , SE-70182 Örebro , Sweden
| | - Yu Song
- Department of Forest Ecology and Management , Swedish University of Agricultural Sciences , SE-901 83 Umeå , Sweden
| | - Jeffra K Schaefer
- Department of Environmental Sciences , Rutgers University , 14 College Farm Road , New Brunswick , New Jersey 08901 , United States
| | - Ulf Skyllberg
- Department of Forest Ecology and Management , Swedish University of Agricultural Sciences , SE-901 83 Umeå , Sweden
| | - Erik Björn
- Department of Chemistry , Umeå University , SE- 90187 Umeå , Sweden
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16
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IdeR, a DtxR Family Iron Response Regulator, Controls Iron Homeostasis, Morphological Differentiation, Secondary Metabolism, and the Oxidative Stress Response in Streptomyces avermitilis. Appl Environ Microbiol 2018; 84:AEM.01503-18. [PMID: 30194099 DOI: 10.1128/aem.01503-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 08/29/2018] [Indexed: 01/29/2023] Open
Abstract
Iron, an essential element for microorganisms, functions as a vital cofactor in a wide variety of key metabolic processes. On the other hand, excess iron may have toxic effects on bacteria by catalyzing the formation of reactive oxygen species through the Fenton reaction. The prevention of iron toxicity requires the precise control of intracellular iron levels in bacteria. Mechanisms of iron homeostasis in the genus Streptomyces (the producers of various antibiotics) are poorly understood. Streptomyces avermitilis is the industrial producer of avermectins, which are potent anthelmintic agents widely used in medicine, agriculture, and animal husbandry. We investigated the regulatory role of IdeR, a DtxR family regulator, in S. avermitilis In the presence of iron, IdeR binds to a specific palindromic consensus sequence in promoters and regulates 14 targets involved in iron metabolism (e.g., iron acquisition, iron storage, heme metabolism, and Fe-S assembly). IdeR also directly regulates 12 targets involved in other biological processes, including morphological differentiation, secondary metabolism, carbohydrate metabolism, and the tricarboxylic acid (TCA) cycle. ideR transcription is positively regulated by the peroxide-sensing transcriptional regulator OxyR. A newly constructed ideR deletion mutant (DideR) was found to be less responsive to iron levels and more sensitive to H2O2 treatment than the wild-type strain, indicating that ideR is essential for oxidative stress responses. Our findings, taken together, demonstrate that IdeR plays a pleiotropic role in the overall coordination of metabolism in Streptomyces spp. in response to iron levels.IMPORTANCE Iron is essential to almost all organisms, but in the presence of oxygen, iron is both poorly available and potentially toxic. Streptomyces species are predominantly present in soil where the environment is complex and fluctuating. So far, the mechanism of iron homeostasis in Streptomyces spp. remains to be elucidated. Here, we characterized the regulatory role of IdeR in the avermectin-producing organism S. avermitilis IdeR maintains intracellular iron levels by regulating genes involved in iron absorption and storage. IdeR also directly regulates morphological differentiation, secondary metabolism, and central metabolism. ideR is under the positive control of OxyR and is indispensable for an efficient response to oxidative stress. This investigation uncovered that IdeR acts as a global regulator coordinating iron homeostasis, morphological differentiation, secondary metabolism, and oxidative stress response in Streptomyces species. Elucidation of the pleiotropic regulation function of IdeR provides new insights into the mechanisms of how Streptomyces spp. adapt to the complex environment.
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17
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Latorre M, Quenti D, Travisany D, Singh KV, Murray BE, Maass A, Cambiazo V. The Role of Fur in the Transcriptional and Iron Homeostatic Response of Enterococcus faecalis. Front Microbiol 2018; 9:1580. [PMID: 30065712 PMCID: PMC6056675 DOI: 10.3389/fmicb.2018.01580] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 06/25/2018] [Indexed: 01/23/2023] Open
Abstract
The ferric uptake regulator (Fur) plays a major role in controlling the expression of iron homeostasis genes in bacterial organisms. In this work, we fully characterized the capacity of Fur to reconfigure the global transcriptional network and influence iron homeostasis in Enterococcus faecalis. The characterization of the Fur regulon from E. faecalis indicated that this protein (Fur) regulated the expression of genes involved in iron uptake systems, conferring to the system a high level of efficiency and specificity to respond under different iron exposure conditions. An RNAseq assay coupled with a systems biology approach allowed us to identify the first global transcriptional network activated by different iron treatments (excess and limited), with and without the presence of Fur. The results showed that changes in iron availability activated a complex network of transcriptional factors in E. faecalis, among them global regulators such as LysR, ArgR, GalRS, and local regulators, LexA and CopY, which were also stimulated by copper and zinc treatments. The deletion of Fur impacted the expression of genes encoding for ABC transporters, energy production and [Fe-S] proteins, which optimized detoxification and iron uptake under iron excess and limitation, respectively. Finally, considering the close relationship between iron homeostasis and pathogenesis, our data showed that the absence of Fur increased the internal concentration of iron in the bacterium and also affected its ability to produce biofilm. These results open new alternatives in the field of infection mechanisms of E. faecalis.
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Affiliation(s)
- Mauricio Latorre
- Laboratorio de Bioinformática y Expresión Génica, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, Santiago, Chile.,Mathomics, Center for Mathematical Modeling, Universidad de Chile, Santiago, Chile.,Center for Genome Regulation (Fondap 15090007), Universidad de Chile, Santiago, Chile.,Instituto de Ciencias de la Ingeniería, Universidad de O'Higgins, Rancagua, Chile
| | - Daniela Quenti
- Laboratorio de Bioinformática y Expresión Génica, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, Santiago, Chile
| | - Dante Travisany
- Mathomics, Center for Mathematical Modeling, Universidad de Chile, Santiago, Chile.,Center for Genome Regulation (Fondap 15090007), Universidad de Chile, Santiago, Chile
| | - Kavindra V Singh
- Division of Infectious Diseases, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, TX, United States.,Center for Antimicrobial Resistance and Microbial Genomics, McGovern Medical School, University of Texas Health Science Center at Houston (UTHealth), Houston, TX, United States
| | - Barbara E Murray
- Division of Infectious Diseases, Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, TX, United States.,Center for Antimicrobial Resistance and Microbial Genomics, McGovern Medical School, University of Texas Health Science Center at Houston (UTHealth), Houston, TX, United States
| | - Alejandro Maass
- Mathomics, Center for Mathematical Modeling, Universidad de Chile, Santiago, Chile.,Center for Genome Regulation (Fondap 15090007), Universidad de Chile, Santiago, Chile.,Department of Mathematical Engineering, Universidad de Chile, Santiago, Chile
| | - Verónica Cambiazo
- Laboratorio de Bioinformática y Expresión Génica, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, Santiago, Chile.,Center for Genome Regulation (Fondap 15090007), Universidad de Chile, Santiago, Chile
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18
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Abstract
Enterococci are important human commensals and significant opportunistic pathogens. Biofilm-related enterococcal infections, such as endocarditis, urinary tract infections, wound and surgical site infections, and medical device-associated infections, often become chronic upon the formation of biofilm. The biofilm matrix establishes properties that distinguish this state from free-living bacterial cells and increase tolerance to antimicrobial interventions. The metabolic versatility of the enterococci is reflected in the diversity and complexity of environments and communities in which they thrive. Understanding metabolic factors governing colonization and persistence in different host niches can reveal factors influencing the transition to biofilm pathogenicity. Here, we report a form of iron-dependent metabolism for Enterococcus faecalis where, in the absence of heme, extracellular electron transfer (EET) and increased ATP production augment biofilm growth. We observe alterations in biofilm matrix depth and composition during iron-augmented biofilm growth. We show that the ldh gene encoding l-lactate dehydrogenase is required for iron-augmented energy production and biofilm formation and promotes EET. Bacterial metabolic versatility can often influence the outcome of host-pathogen interactions, yet causes of metabolic shifts are difficult to resolve. The bacterial biofilm matrix provides the structural and functional support that distinguishes this state from free-living bacterial cells. Here, we show that the biofilm matrix can immobilize iron, providing access to this growth-promoting resource which is otherwise inaccessible in the planktonic state. Our data show that in the absence of heme, Enterococcus faecalisl-lactate dehydrogenase promotes EET and uses matrix-associated iron to carry out EET. Therefore, the presence of iron within the biofilm matrix leads to enhanced biofilm growth.
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19
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Ueki T, Nevin KP, Woodard TL, Lovley DR. Genetic switches and related tools for controlling gene expression and electrical outputs of Geobacter sulfurreducens. J Ind Microbiol Biotechnol 2016; 43:1561-1575. [PMID: 27659960 DOI: 10.1007/s10295-016-1836-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 09/11/2016] [Indexed: 01/04/2023]
Abstract
Physiological studies and biotechnology applications of Geobacter species have been limited by a lack of genetic tools. Therefore, potential additional molecular strategies for controlling metabolism were explored. When the gene for citrate synthase, or acetyl-CoA transferase, was placed under the control of a LacI/IPTG regulator/inducer system, cells grew on acetate only in the presence of IPTG. The TetR/AT system could also be used to control citrate synthase gene expression and acetate metabolism. A strain that required IPTG for growth on D-lactate was constructed by placing the gene for D-lactate dehydrogenase under the control of the LacI/IPTG system. D-Lactate served as an inducer in a strain in which a D-lactate responsive promoter and transcription repressor were used to control citrate synthase expression. Iron- and potassium-responsive systems were successfully incorporated to regulate citrate synthase expression and growth on acetate. Linking the appropriate degradation tags on the citrate synthase protein made it possible to control acetate metabolism with either the endogenous ClpXP or exogenous Lon protease and tag system. The ability to control current output from Geobacter biofilms and the construction of an AND logic gate for acetate metabolism suggested that the tools developed may be applicable for biosensor and biocomputing applications.
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Affiliation(s)
- Toshiyuki Ueki
- Department of Microbiology, University of Massachusetts, Morrill Science Center IV North, 639 North Pleasant Street, Amherst, MA, 01003, USA.
| | - Kelly P Nevin
- Department of Microbiology, University of Massachusetts, Morrill Science Center IV North, 639 North Pleasant Street, Amherst, MA, 01003, USA
| | - Trevor L Woodard
- Department of Microbiology, University of Massachusetts, Morrill Science Center IV North, 639 North Pleasant Street, Amherst, MA, 01003, USA
| | - Derek R Lovley
- Department of Microbiology, University of Massachusetts, Morrill Science Center IV North, 639 North Pleasant Street, Amherst, MA, 01003, USA
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20
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Ding D, Li L, Shu C, Sun X. K-shell Analysis Reveals Distinct Functional Parts in an Electron Transfer Network and Its Implications for Extracellular Electron Transfer. Front Microbiol 2016; 7:530. [PMID: 27148219 PMCID: PMC4837345 DOI: 10.3389/fmicb.2016.00530] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/31/2016] [Indexed: 01/17/2023] Open
Abstract
Shewanella oneidensis MR-1 is capable of extracellular electron transfer (EET) and hence has attracted considerable attention. The EET pathways mainly consist of c-type cytochromes, along with some other proteins involved in electron transfer processes. By whole genome study and protein interactions inquisition, we constructed a large-scale electron transfer network containing 2276 interactions among 454 electron transfer related proteins in S. oneidensis MR-1. Using the k-shell decomposition method, we identified and analyzed distinct parts of the electron transfer network. We found that there was a negative correlation between the k s (k-shell values) and the average DR_100 (disordered regions per 100 amino acids) in every shell, which suggested that disordered regions of proteins played an important role during the formation and extension of the electron transfer network. Furthermore, proteins in the top three shells of the network are mainly located in the cytoplasm and inner membrane; these proteins can be responsible for transfer of electrons into the quinone pool in a wide variety of environmental conditions. In most of the other shells, proteins are broadly located throughout the five cellular compartments (cytoplasm, inner membrane, periplasm, outer membrane, and extracellular), which ensures the important EET ability of S. oneidensis MR-1. Specifically, the fourth shell was responsible for EET and the c-type cytochromes in the remaining shells of the electron transfer network were involved in aiding EET. Taken together, these results show that there are distinct functional parts in the electron transfer network of S. oneidensis MR-1, and the EET processes could achieve high efficiency through cooperation through such an electron transfer network.
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Affiliation(s)
- Dewu Ding
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast UniversityNanjing, China; Department of Mathematics and Computer Science, Chizhou CollegeChizhou, China
| | - Ling Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University Nanjing, China
| | - Chuanjun Shu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University Nanjing, China
| | - Xiao Sun
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University Nanjing, China
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21
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Hu YH, Sun L. The global regulatory effect of Edwardsiella tarda Fur on iron acquisition, stress resistance, and host infection: A proteomics-based interpretation. J Proteomics 2016; 140:100-10. [PMID: 27102497 DOI: 10.1016/j.jprot.2016.04.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/27/2016] [Accepted: 04/07/2016] [Indexed: 02/01/2023]
Abstract
UNLABELLED Ferric uptake regulator (Fur) is an important transcriptional regulator of Gram-negative bacteria. Edwardsiella tarda is a severe fish bacterial pathogen with a broad host range that includes humans. In this study, we examined the regulatory function of Fur in E. tarda via a proteomic approach. Compared to the wild type TX01, the fur mutant TX01Δfur exhibited (i) retarded growth, (ii) enhanced siderophore production, (iii) increased acid tolerance, which is in contrast to observations in other bacterial species, (iv) decreased survival against oxidative stress and host serum, (v) impaired ability to inhibit host immune response, (vi) attenuated tissue infectivity and overall virulence. The deficiency of TX01Δfur was rescued by introduction of an exogenous fur gene. iTRAQ-based comparative proteomic analysis of TX01Δfur and TX01 identified 89 differentially expressed proteins that cover a wide range of functional categories including those affected by fur mutation. In addition, 16 proteins were identified for the first time to be regulated by Fur in Gram-negative bacteria. These results provide the first protein-based interpretation of the global impact of Fur on the physiology and infectivity of E. tarda. SIGNIFICANCE This study demonstrates that in E. tarda, Fur controls multiple aspects of bacterial life, including growth, metabolism, iron acquisition, stress response, and host infection. In line with these observations, proteomics analysis identified a large amount of proteins affected in expression by Fur, which are involved in bacterial physiology and infectivity. Hence, these results link for the first time the pleiotropic effect of Fur with global protein expression and shed new light on the function and regulatory mechanism of Fur in pathogenic bacteria.
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Affiliation(s)
- Yong-Hua Hu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - Li Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
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22
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Iron management and production of electricity by microorganisms. Appl Microbiol Biotechnol 2015; 99:8329-36. [DOI: 10.1007/s00253-015-6897-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 07/27/2015] [Accepted: 07/30/2015] [Indexed: 10/23/2022]
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23
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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. ENVIRONMENTAL MICROBIOLOGY REPORTS 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] [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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24
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Seo SW, Kim D, Latif H, O'Brien EJ, Szubin R, Palsson BO. Deciphering Fur transcriptional regulatory network highlights its complex role beyond iron metabolism in Escherichia coli. Nat Commun 2014; 5:4910. [PMID: 25222563 PMCID: PMC4167408 DOI: 10.1038/ncomms5910] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 08/05/2014] [Indexed: 02/07/2023] Open
Abstract
The ferric uptake regulator (Fur) plays a critical role in the transcriptional regulation of iron metabolism. However, the full regulatory potential of Fur remains undefined. Here we comprehensively reconstruct the Fur transcriptional regulatory network in Escherichia coli K-12 MG1655 in response to iron availability using genome-wide measurements (ChIP-exo and RNA-seq). Integrative data analysis reveals that a total of 81 genes in 42 transcription units are directly regulated by three different modes of Fur regulation, including apo- and holo-Fur activation and holo-Fur repression. We show that Fur connects iron transport and utilization enzymes with negative-feedback loop pairs for iron homeostasis. In addition, direct involvement of Fur in the regulation of DNA synthesis, energy metabolism, and biofilm development is found. These results show how Fur exhibits a comprehensive regulatory role affecting many fundamental cellular processes linked to iron metabolism in order to coordinate the overall response of E. coli to iron availability.
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Affiliation(s)
- Sang Woo Seo
- 1] Department of Bioengineering, University of California San Diego, La Jolla, California 92093-0412, USA [2]
| | - Donghyuk Kim
- 1] Department of Bioengineering, University of California San Diego, La Jolla, California 92093-0412, USA [2]
| | - Haythem Latif
- 1] Department of Bioengineering, University of California San Diego, La Jolla, California 92093-0412, USA [2]
| | - Edward J O'Brien
- Department of Bioengineering, University of California San Diego, La Jolla, California 92093-0412, USA
| | - Richard Szubin
- Department of Bioengineering, University of California San Diego, La Jolla, California 92093-0412, USA
| | - Bernhard O Palsson
- 1] Department of Bioengineering, University of California San Diego, La Jolla, California 92093-0412, USA [2] Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Lyngby, Denmark
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