1
|
Ortiz-Medina JF, Poole MR, Grunden AM, Call DF. Nitrogen Fixation and Ammonium Assimilation Pathway Expression of Geobacter sulfurreducens Changes in Response to the Anode Potential in Microbial Electrochemical Cells. Appl Environ Microbiol 2023; 89:e0207322. [PMID: 36975810 PMCID: PMC10132095 DOI: 10.1128/aem.02073-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 03/07/2023] [Indexed: 03/29/2023] Open
Abstract
Nitrogen gas (N2) fixation in the anode-respiring bacterium Geobacter sulfurreducens occurs through complex, multistep processes. Optimizing ammonium (NH4+) production from this bacterium in microbial electrochemical technologies (METs) requires an understanding of how those processes are regulated in response to electrical driving forces. In this study, we quantified gene expression levels (via RNA sequencing) of G. sulfurreducens growing on anodes fixed at two different potentials (-0.15 V and +0.15 V versus standard hydrogen electrode). The anode potential had a significant impact on the expression levels of N2 fixation genes. At -0.15 V, the expression of nitrogenase genes, such as nifH, nifD, and nifK, significantly increased relative to that at +0.15 V, as well as genes associated with NH4+ uptake and transformation, such as glutamine and glutamate synthetases. Metabolite analysis confirmed that both of these organic compounds were present in significantly higher intracellular concentrations at -0.15 V. N2 fixation rates (estimated using the acetylene reduction assay and normalized to total protein) were significantly larger at -0.15 V. Genes expressing flavin-based electron bifurcation complexes, such as electron-transferring flavoproteins (EtfAB) and the NADH-dependent ferredoxin:NADP reductase (NfnAB), were also significantly upregulated at -0.15 V, suggesting that these mechanisms may be involved in N2 fixation at that potential. Our results show that in energy-constrained situations (i.e., low anode potential), the cells increase per-cell respiration and N2 fixation rates. We hypothesize that at -0.15 V, they increase N2 fixation activity to help maintain redox homeostasis, and they leverage electron bifurcation as a strategy to optimize energy generation and use. IMPORTANCE Biological nitrogen fixation coupled with ammonium recovery provides a sustainable alternative to the carbon-, water-, and energy-intensive Haber-Bosch process. Aerobic biological nitrogen fixation technologies are hindered by oxygen gas inhibition of the nitrogenase enzyme. Electrically driving biological nitrogen fixation in anaerobic microbial electrochemical technologies overcomes this challenge. Using Geobacter sulfurreducens as a model exoelectrogenic diazotroph, we show that the anode potential in microbial electrochemical technologies has a significant impact on nitrogen gas fixation rates, ammonium assimilation pathways, and expression of genes associated with nitrogen gas fixation. These findings have important implications for understanding regulatory pathways of nitrogen gas fixation and will help identify target genes and operational strategies to enhance ammonium production in microbial electrochemical technologies.
Collapse
Affiliation(s)
- Juan F. Ortiz-Medina
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Mark R. Poole
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Amy M. Grunden
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, USA
| | - Douglas F. Call
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USA
| |
Collapse
|
2
|
Belleville P, Merlin G, Ramousse J, Deseure J. Characterization of spatiotemporal electroactive anodic biofilm activity distribution using 1D simulations. Sci Rep 2022; 12:5849. [PMID: 35393459 PMCID: PMC8990003 DOI: 10.1038/s41598-022-09596-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 03/14/2022] [Indexed: 11/17/2022] Open
Abstract
Activity distribution limitation in electroactive biofilm remains an unclear phenomenon. Some observations using confocal microscopy have shown notable difference between activity close to the anode and activity at the liquid interface. A numerical model is developed in this work to describe biofilm growth and local biomass segregation in electroactive biofilm. Under our model hypothesis, metabolic activity distribution in the biofilm results from the competition between two limiting factors: acetate diffusion and electronic conduction in the biofilm. Influence of inactive biomass fraction (i.e. non-growing biomass fraction) properties (such as conductivity and density) is simulated to show variation in local biomass distribution. Introducing a dependence of effective diffusion to local density leads to a drastic biomass fraction segregation. Increasing density of inactive fraction reduces significantly acetate diffusion in biofilm, enhances biomass activity on the outer layer (liquid/biofilm interface) and maintains inner core largely inactive. High inactive fraction conductivity enhances biomass activity in the outer layer and enhances current production. Hence, investment in extracellular polymer substance (EPS), anchoring redox components, is benefit for biofilm electroactivity. However, under our model hypothesis it means that conductivity should be two order lower than biofilm conductivity reported in order to observe inner core active biomass segregation.
Collapse
Affiliation(s)
- Pierre Belleville
- Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP Institute of Engineering, LEPMI, 38000, Grenoble, France.,Univ. Savoie Mont-Blanc, CNRS, LOCIE, UMR 5271, Polytech Annecy, Chambéry, bât. Helios, 60 rue du lac Léman, Savoie Technolac, 73370, Le Bourget du Lac, France
| | - Gerard Merlin
- Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP Institute of Engineering, LEPMI, 38000, Grenoble, France.,Univ. Savoie Mont-Blanc, CNRS, LOCIE, UMR 5271, Polytech Annecy, Chambéry, bât. Helios, 60 rue du lac Léman, Savoie Technolac, 73370, Le Bourget du Lac, France
| | - Julien Ramousse
- Univ. Savoie Mont-Blanc, CNRS, LOCIE, UMR 5271, Polytech Annecy, Chambéry, bât. Helios, 60 rue du lac Léman, Savoie Technolac, 73370, Le Bourget du Lac, France
| | - Jonathan Deseure
- Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP Institute of Engineering, LEPMI, 38000, Grenoble, France.
| |
Collapse
|
3
|
Scarabotti F, Rago L, Bühler K, Harnisch F. The electrode potential determines the yield coefficients of early-stage Geobacter sulfurreducens biofilm anodes. Bioelectrochemistry 2021; 140:107752. [PMID: 33618189 DOI: 10.1016/j.bioelechem.2021.107752] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/29/2021] [Accepted: 01/30/2021] [Indexed: 01/05/2023]
Abstract
Geobacter sulfurreducens is the model for electroactive microorganisms (EAM). EAM can use solid state terminal electron acceptors (TEA) including anodes via extracellular electron transfer (EET). Yield coefficients relate the produced cell number or biomass to the oxidized substrate or the reduced TEA. These data are not yet sufficiently available for EAM growing at anodes. Thus, this study provides information about kinetics as well as yield coefficients of early-stage G. sulfurreducens biofilms using anodes as TEA at the potentials of -200 mV, 0 mV and +200 mV (vs. Ag/AgCl sat. KCl). The selected microorganism was therefore cultivated in single and double chamber batch reactors on graphite or AuPd anodes. Interestingly, whereas the lag time and maximum current density within 12 days of growth differed, the anode potential does not influence the coulombic efficiency and the formal potential of the EET, which remains constant for all the experiments at ~ -300 to -350 mV. We demonstrated for the first time that the anode potential has a strong influence on single cell yield coefficients which ranged from 2.69 × 1012 cells mole--1 at -200 mV and 1.48 × 1012 cells mole--1 at 0 mV to 2.58 × 1011 cells mole--1 at +200 mV in single chamber reactors and from 1.15 × 1012 cells mole--1 at -200 mV to 8.98× 1011 cells mole--1 at 0 mV in double chamber reactors. This data can be useful for optimization and scaling-up of primary microbial electrochemical technologies.
Collapse
Affiliation(s)
- Francesco Scarabotti
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Laura Rago
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Katja Bühler
- Department Solar Materials, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Falk Harnisch
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany.
| |
Collapse
|
4
|
A chip-based 128-channel potentiostat for high-throughput studies of bioelectrochemical systems: Optimal electrode potentials for anodic biofilms. Biosens Bioelectron 2020; 174:112813. [PMID: 33303324 DOI: 10.1016/j.bios.2020.112813] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 11/04/2020] [Accepted: 11/08/2020] [Indexed: 11/21/2022]
Abstract
The presence of microorganisms performing extracellular electron transfer has been established in many environments. Research to determine their role is moving slowly due to the high cost of potentiostats and the variance of data with small number of replicates. Here, we present a 128-channel potentiostat, connected to a 128 gold electrode array. Whereas the system is able to perform simultaneously 128 (bio)electrochemical measurements with an independent electrical signal input, the present manufacturing of the array limited the number of effective channels for this study to 77. We assessed the impact of 11 electrode potentials ranging from -0.45V to +0.2V vs. Ag/AgCl (7 replicates per potential) on the growth and electrochemical characteristics of anodic electroactive biofilms (EABs) formed by acetate-fed microbial communities. After 7 days of growth, maximum current was reached for electrodes poised at -0.3V, closely followed by -0.25V and -0.1V to +0.1V, a range well-fitting the midpoint potential of minerals naturally reduced by electroactive bacteria such as Geobacter Sulfurreducens. There was no significant difference in apparent midpoint potential of the EABs (-0.35V), suggesting that the mechanism of heterogeneous electron transfer was not affected by the electrode potential. The EABs poised below current plateau potential (≤-0.3V) exhibited slower growth but higher charge transfer parameters. The high-throughput and high reproducibility provided by the array may have a major facilitating impact on the field of electromicrobiology. Key aspects to improve are data processing algorithms to deal with the vast amount of generated data, and manufacturing of the electrode array itself.
Collapse
|
5
|
Strategies for improving the electroactivity and specific metabolic functionality of microorganisms for various microbial electrochemical technologies. Biotechnol Adv 2019; 39:107468. [PMID: 31707076 DOI: 10.1016/j.biotechadv.2019.107468] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 11/02/2019] [Accepted: 11/04/2019] [Indexed: 01/31/2023]
Abstract
Electroactive microorganisms, which possess extracellular electron transfer (EET) capabilities, are the basis of microbial electrochemical technologies (METs) such as microbial fuel and electrolysis cells. These are considered for several applications ranging from the energy-efficient treatment of waste streams to the production of value-added chemicals and fuels, bioremediation, and biosensing. Various aspects related to the microorganisms, electrodes, separators, reactor design, and operational or process parameters influence the overall functioning of METs. The most fundamental and critical performance-determining factor is, however, the microorganism-electrode interactions. Modification of the electrode surfaces and microorganisms for optimizing their interactions has therefore been the major MET research focus area over the last decade. In the case of microorganisms, primarily their EET mechanisms and efficiencies along with the biofilm formation capabilities, collectively considered as microbial electroactivity, affect their interactions with the electrodes. In addition to electroactivity, the specific metabolic or biochemical functionality of microorganisms is equally crucial to the target MET application. In this article, we present the major strategies that are used to enhance the electroactivity and specific functionality of microorganisms pertaining to both anodic and cathodic processes of METs. These include simple physical methods based on the use of heat and magnetic field along with chemical, electrochemical, and growth media amendment approaches to the complex procedure-based microbial bioaugmentation, co-culture, and cell immobilization or entrapment, and advanced toolkit-based biofilm engineering, genetic modifications, and synthetic biology strategies. We further discuss the applicability and limitations of these strategies and possible future research directions for advancing the highly promising microbial electrochemistry-driven biotechnology.
Collapse
|
6
|
Li DB, Huang YX, Li J, Li LL, Tian LJ, Yu HQ. Electrochemical activities of Geobacter biofilms growing on electrodes with various potentials. Electrochim Acta 2017. [DOI: 10.1016/j.electacta.2016.12.146] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
7
|
Jain P, Sharma M, Dureja P, Sarma PM, Lal B. Bioelectrochemical approaches for removal of sulfate, hydrocarbon and salinity from produced water. CHEMOSPHERE 2017; 166:96-108. [PMID: 27689889 DOI: 10.1016/j.chemosphere.2016.09.081] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 09/18/2016] [Accepted: 09/19/2016] [Indexed: 05/07/2023]
Abstract
Produced water (PW) is the largest liquid waste stream generated during the exploration and drilling process of both the conventional hydrocarbon based resources like crude oil and natural gas, as well as the new fossil resources like shale gas and coal bed methane. Resource management, efficient utilization of the water resources, and water purification protocols are the conventionally used treatment methods applied to either treat or utilize the generated PW. This review provides a comprehensive overview of these conventional PW treatment strategies with special emphasises on electrochemical treatment. Key considerations associated with these approaches for efficient treatment of PW are also discussed. After a thorough assessment of the salient features of these treatment platforms, we propose a new strategy of uniquely integrating bioelectrochemical processes with biological system for more effective PW treatment and management.
Collapse
Affiliation(s)
- Pratiksha Jain
- TERI University, 10, Institutional Area, VasantKunj, New Delhi, India; The Energy and Resources Institute, India Habitat Centre, Lodhi Road, New Delhi, India
| | - Mohita Sharma
- The Energy and Resources Institute, India Habitat Centre, Lodhi Road, New Delhi, India
| | - Prem Dureja
- The Energy and Resources Institute, India Habitat Centre, Lodhi Road, New Delhi, India
| | | | - Banwari Lal
- TERI University, 10, Institutional Area, VasantKunj, New Delhi, India; The Energy and Resources Institute, India Habitat Centre, Lodhi Road, New Delhi, India.
| |
Collapse
|
8
|
Kokko ME, Mäkinen AE, Sulonen ML, Puhakka JA. Effects of anode potentials on bioelectrogenic conversion of xylose and microbial community compositions. Biochem Eng J 2015. [DOI: 10.1016/j.bej.2015.06.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|