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Bird LJ, Leary DH, Hervey J, Compton J, Phillips D, Tender LM, Voigt CA, Glaven SM. Marine Biofilm Engineered to Produce Current in Response to Small Molecules. ACS Synth Biol 2023; 12:1007-1020. [PMID: 36926839 DOI: 10.1021/acssynbio.2c00417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
Engineered electroactive bacteria have potential applications ranging from sensing to biosynthesis. In order to advance the use of engineered electroactive bacteria, it is important to demonstrate functional expression of electron transfer modules in chassis adapted to operationally relevant conditions, such as non-freshwater environments. Here, we use the Shewanella oneidensis electron transfer pathway to induce current production in a marine bacterium, Marinobacter atlanticus, during biofilm growth in artificial seawater. Genetically encoded sensors optimized for use in Escherichia coli were used to control protein expression in planktonic and biofilm attached cells. Significant current production required the addition of menaquinone, which M. atlanticus does not produce, for electron transfer from the inner membrane to the expressed electron transfer pathway. Current through the S. oneidensis pathway in M. atlanticus was observed when inducing molecules were present during biofilm formation. Electron transfer was also reversible, indicating that electron transfer into M. atlanticus could be controlled. These results show that an operationally relevant marine bacterium can be genetically engineered for environmental sensing and response using an electrical signal.
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Affiliation(s)
- Lina J Bird
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Dagmar H Leary
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Judson Hervey
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Jaimee Compton
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Daniel Phillips
- Biochemistry Branch, Oak Ridge Institute for Science and Education/US Army DEVCOM Chemical Biological Center, Aberdeen Proving Grounds, Maryland 21005, United States
| | - Leonard M Tender
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Christopher A Voigt
- Department of Biological Engineering and the Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sarah M Glaven
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States
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Bird LJ, Mickol RL, Eddie BJ, Thakur M, Yates MD, Glaven SM. Marinobacter: A case study in bioelectrochemical chassis evaluation. Microb Biotechnol 2023; 16:494-506. [PMID: 36464922 PMCID: PMC9948230 DOI: 10.1111/1751-7915.14170] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 10/28/2022] [Accepted: 11/03/2022] [Indexed: 12/08/2022] Open
Abstract
The junction of bioelectrochemical systems and synthetic biology opens the door to many potentially groundbreaking technologies. When developing these possibilities, choosing the correct chassis organism can save a great deal of engineering effort and, indeed, can mean the difference between success and failure. Choosing the correct chassis for a specific application requires a knowledge of the metabolic potential of the candidate organisms, as well as a clear delineation of the traits, required in the application. In this review, we will explore the metabolic and electrochemical potential of a single genus, Marinobacter. We will cover its strengths, (salt tolerance, biofilm formation and electrochemical potential) and weaknesses (insufficient characterization of many strains and a less developed toolbox for genetic manipulation) in potential synthetic electromicrobiology applications. In doing so, we will provide a roadmap for choosing a chassis organism for bioelectrochemical systems.
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Affiliation(s)
- Lina J. Bird
- Center for Bio/Molecular Science and Engineering, Naval Research LaboratoryWashingtonDistrict of ColumbiaUSA
| | - Rebecca L. Mickol
- Center for Bio/Molecular Science and Engineering, Naval Research LaboratoryWashingtonDistrict of ColumbiaUSA
| | - Brian J. Eddie
- Center for Bio/Molecular Science and Engineering, Naval Research LaboratoryWashingtonDistrict of ColumbiaUSA
| | - Meghna Thakur
- Center for Bio/Molecular Science and Engineering, Naval Research LaboratoryWashingtonDistrict of ColumbiaUSA
- College of Science, George Mason UniversityFairfaxVirginiaUSA
| | - Matthew D. Yates
- Center for Bio/Molecular Science and Engineering, Naval Research LaboratoryWashingtonDistrict of ColumbiaUSA
| | - Sarah M. Glaven
- Center for Bio/Molecular Science and Engineering, Naval Research LaboratoryWashingtonDistrict of ColumbiaUSA
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Eddie BJ, Malanoski AP, Onderko EL, Phillips DA, Glaven SM. Marinobacter atlanticus electrode biofilms differentially regulate gene expression depending on electrode potential and lifestyle. Biofilm 2021; 3:100051. [PMID: 34195607 PMCID: PMC8233155 DOI: 10.1016/j.bioflm.2021.100051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/13/2021] [Accepted: 06/07/2021] [Indexed: 11/18/2022] Open
Abstract
Marinobacter spp. are opportunitrophs with a broad metabolic range including interactions with metals and electrodes. Marinobacter atlanticus strain CP1 was previously isolated from a cathode biofilm microbial community enriched from a sediment microbial fuel cell. Like other Marinobacter spp., M. atlanticus generates small amounts of electrical current when grown as a biofilm on an electrode, which is enhanced by the addition of redox mediators. However, the molecular mechanism resulting in extracellular electron transfer is unknown. Here, RNA-sequencing was used to determine changes in gene expression in electrode-attached and planktonic cells of M. atlanticus when grown at electrode potentials that enable current production (310 and 510 mV vs. SHE) compared to a potential that enables electron uptake (160 mV). Cells grown at current-producing potentials had increased expression of genes for molybdate transport, regardless of planktonic or attached lifestyle. Electrode-attached cells at current-producing potentials showed increased expression of the major export protein for the type VI secretion system. Growth at 160 mV resulted in an increase in expression of genes related to stress response and DNA repair including both RecBCD and the LexA/RecA regulatory network, as well as genes for copper homeostasis. Changes in expression of proteins with PEP C-terminal extracellular export motifs suggests that M. atlanticus is remodeling the biofilm matrix in response to electrode potential. These results improve our understanding of the physiological adaptations required for M. atlanticus growth on electrodes, and suggest a role for metal acquisition, either as a requirement for metal cofactors of redox proteins or as a possible electron shuttling mechanism.
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Affiliation(s)
- Brian J. Eddie
- Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC, 20375, USA
| | | | | | - Daniel A. Phillips
- Oak Ridge Institute for Science and Education / US Army DEVCOM Chemical Biological Center, Biochemistry Branch, Aberdeen Proving Grounds, MD, 21010 USA
| | - Sarah M. Glaven
- Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC, 20375, USA
- Corresponding author. 4555 Overlook Ave, Washington, DC, 20375.
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Evidence for Horizontal and Vertical Transmission of Mtr-Mediated Extracellular Electron Transfer among the Bacteria. mBio 2021; 13:e0290421. [PMID: 35100867 PMCID: PMC8805035 DOI: 10.1128/mbio.02904-21] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some bacteria and archaea have evolved the means to use extracellular electron donors and acceptors for energy metabolism, a phenomenon broadly known as extracellular electron transfer (EET). One such EET mechanism is the transmembrane electron conduit MtrCAB, which has been shown to transfer electrons derived from metabolic substrates to electron acceptors, like Fe(III) and Mn(IV) oxides, outside the cell. Although most studies of MtrCAB-mediated EET have been conducted in Shewanella oneidensis MR-1, recent investigations in Vibrio and Aeromonas species have revealed that the electron-donating proteins that support MtrCAB in Shewanella are not as representative as previously thought. This begs the question of how widespread the capacity for MtrCAB-mediated EET is, the changes it has accrued in different lineages, and where these lineages persist today. Here, we employed a phylogenetic and comparative genomics approach to identify the MtrCAB system across all domains of life. We found mtrCAB in the genomes of numerous diverse Bacteria from a wide range of environments, and the patterns therein strongly suggest that mtrCAB was distributed through both horizontal and subsequent vertical transmission, and with some cases indicating downstream modular diversification of both its core and accessory components. Our data point to an emerging evolutionary story about metal-oxidizing and -reducing metabolism, demonstrates that this capacity for EET has broad relevance to a diversity of taxa and the biogeochemical cycles they drive, and lays the foundation for further studies to shed light on how this mechanism may have coevolved with Earth's redox landscape. IMPORTANCE While many metabolisms make use of soluble, cell-permeable substrates like oxygen or hydrogen, there are other substrates, like iron or manganese, that cannot be brought into the cell. Some bacteria and archaea have evolved the means to directly "plug in" to such environmental electron reservoirs in a process known as extracellular electron transfer (EET), making them powerful agents of biogeochemical change and promising vehicles for bioremediation and alternative energy. Yet the diversity, distribution, and evolution of EET mechanisms are poorly constrained. Here, we present findings showing that the genes encoding one such EET system (mtrCAB) are present in a broad diversity of bacteria found in a wide range of environments, emphasizing the ubiquity and potential impact of EET in our biosphere. Our results suggest that these genes have been disseminated largely through horizontal transfer, and the changes they have accrued in these lineages potentially reflect adaptations to changing environments.
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Electrochemical and phylogenetic comparisons of oxygen-reducing electroautotrophic communities. Biosens Bioelectron 2021; 171:112700. [PMID: 33096434 DOI: 10.1016/j.bios.2020.112700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 10/05/2020] [Accepted: 10/06/2020] [Indexed: 11/21/2022]
Abstract
The mechanisms of extracellular electron transfer and the microbial taxa associated with the observed electroactivity are fundamental to oxygen-reducing microbial cathodes. Here we confirmed the apparent 'electroautotrophic' behavior of electroactive biofilms (EABs) grown on carbon electrodes at + 0.20V vs. Ag/AgCl under air. The EABs catalyzed O2 electroreduction into water ─ as demonstrated by a rotating ring disc experiment ─ and performed quasi-reversible heterogeneous electron transfer (HET). By using electrodes of low surface capacitance, we report for the first time nonturnover redox peaks that are very likely intrinsic to the redox protein(s) performing the HET. Because the formal potential of redox proteins is pH-dependent, we investigated the evolution of characteristic potentials of the EABs with the solution pH: (i) open circuit potential, (ii) half-wave potential, and (iii) averaged peak potential of nonturnover cyclic voltammograms, which is presumably the formal potential of the primary electron acceptor(s) for the community. In addition to describing the redox thermodynamics behind HET, we suggest that the corresponding data provides an electrochemical fingerprint that could help in comparing the electroactivity of diverse microbial communities. The taxon with the highest relative abundance in our EABs was an unclassified member of the Gammaproteobacteria that was phylogenetically closely related to most other abundant unclassified Gammaproteobacteria commonly reported in EABs reducing O2 at high potentials, further suggesting that those taxa are responsible for the bioelectroactivity. Phylogenetic and electrochemical similarities between reported EABs jointly support the hypothesis that similar biomolecular mechanisms may be responsible for this highly probable electroautotrophic metabolism.
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Rimboud M, Barakat M, Achouak W, Bergel A, Délia ML. Oxygen-reducing microbial cathodes in hypersaline electrolyte. BIORESOURCE TECHNOLOGY 2021; 319:124165. [PMID: 33039843 DOI: 10.1016/j.biortech.2020.124165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/16/2020] [Accepted: 09/19/2020] [Indexed: 06/11/2023]
Abstract
Hypersaline electrolytes offer a way to boost the development of microbial fuel cells by overcoming the issue due to the low conductivity of the usual media. Efficient halotolerant bioanodes have already been designed but O2-reducing cathodes remain a strong bottleneck. Here, O2-reducing biocathodes were designed by using salt marsh sediment as the inoculum and a hypersaline media (45 g/L NaCl) of high conductivity (10.4 S m-1). Current density up to 2.2 A m-2 was reached from potential of +0.2 V/SCE. The efficiency of the biocathodes was correlated to the presence of Gammaproteobacteria strain(s) related to Thiohalobacter thiocyanaticus, which were considerably enriched in the best performing biocathodes. This work opens up new perspectives to overcome the O2 reduction issue in hypersaline MFCs by designing efficient halotolerant microbial cathodes and pointing out the strains that should now be focused to improve them.
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Affiliation(s)
- Mickaël Rimboud
- Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Allée Emile Monso, 31432 Toulouse, France
| | - Mohamed Barakat
- Laboratoire d'Ecologie Microbienne de la Rhizosphère et des Environnements Extrêmes (LEMIRE), BIAM, UMR 7265, CEA-CNRS-Aix Marseille Université, CEA Cadarache, 13108 Saint Paul Lez Durance, France
| | - Wafa Achouak
- Laboratoire d'Ecologie Microbienne de la Rhizosphère et des Environnements Extrêmes (LEMIRE), BIAM, UMR 7265, CEA-CNRS-Aix Marseille Université, CEA Cadarache, 13108 Saint Paul Lez Durance, France
| | - Alain Bergel
- Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Allée Emile Monso, 31432 Toulouse, France
| | - Marie-Line Délia
- Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Allée Emile Monso, 31432 Toulouse, France.
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Rimboud M, Achouak W. Electroautotrophy of Thioalkalivibrio nitratireducens. Bioelectrochemistry 2019; 126:48-55. [DOI: 10.1016/j.bioelechem.2018.11.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 11/05/2018] [Accepted: 11/05/2018] [Indexed: 10/27/2022]
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Bird LJ, Wang Z, Malanoski AP, Onderko EL, Johnson BJ, Moore MH, Phillips DA, Chu BJ, Doyle JF, Eddie BJ, Glaven SM. Development of a Genetic System for Marinobacter atlanticus CP1 ( sp. nov.), a Wax Ester Producing Strain Isolated From an Autotrophic Biocathode. Front Microbiol 2018; 9:3176. [PMID: 30622527 PMCID: PMC6308636 DOI: 10.3389/fmicb.2018.03176] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 12/07/2018] [Indexed: 11/13/2022] Open
Abstract
Here, we report on the development of a genetic system for Marinobacter sp. strain CP1, previously isolated from the Biocathode MCL community and shown to oxidize iron and grow as a cathodic biofilm. Sequence analysis of the small and large subunits of the 16S rRNA gene of CP1, as well as comparison of select conserved proteins, indicate that it is most closely related to Marinobacter adhaerens HP15 and Marinobacter sp. ES.042. In silico DNA–DNA hybridization using the genome-to-genome distance calculator (GGDC) predicts CP1 to be a new species of Marinobacter described here as Marinobacter atlanticus. CP1 is competent for transformation with plasmid DNA using conjugation with Escherichia coli donor strain WM3064 and constitutive expression of green fluorescent protein (GFP) is stable in the absence of antibiotic selection. Targeted double deletion mutagenesis of homologs for the M. aquaeoli fatty acyl-CoA reductase (acrB) and fatty aldehyde reductase (farA) genes resulted in a loss of production of wax esters; however, single deletion mutants for either gene resulted in an increase in total wax esters recovered. Genetic tools presented here for CP1 will enable further exploration of wax ester synthesis for biotechnological applications, as well as furthering our efforts to understand the role of CP1 within the Biocathode MCL community.
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Affiliation(s)
- Lina J Bird
- National Research Council, Washington, DC, United States
| | - Zheng Wang
- Center for Biomolecular Science and Engineering, United States Naval Research Laboratory, Washington, DC, United States
| | - Anthony P Malanoski
- Center for Biomolecular Science and Engineering, United States Naval Research Laboratory, Washington, DC, United States
| | | | - Brandy J Johnson
- Center for Biomolecular Science and Engineering, United States Naval Research Laboratory, Washington, DC, United States
| | - Martin H Moore
- Center for Biomolecular Science and Engineering, United States Naval Research Laboratory, Washington, DC, United States
| | - Daniel A Phillips
- American Society For Engineering Education, Washington, DC, United States
| | - Brandon J Chu
- Fischell Department of Bioengineering, University of Maryland, College Park, College Park, MD, United States
| | | | - Brian J Eddie
- Center for Biomolecular Science and Engineering, United States Naval Research Laboratory, Washington, DC, United States
| | - Sarah M Glaven
- Center for Biomolecular Science and Engineering, United States Naval Research Laboratory, Washington, DC, United States
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Malanoski AP, Lin B, Eddie BJ, Wang Z, Hervey WJ, Glaven SM. Relative abundance of 'Candidatus Tenderia electrophaga' is linked to cathodic current in an aerobic biocathode community. Microb Biotechnol 2017; 11:98-111. [PMID: 28696003 PMCID: PMC5743799 DOI: 10.1111/1751-7915.12757] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 06/01/2017] [Accepted: 06/02/2017] [Indexed: 01/18/2023] Open
Abstract
Biocathode microbial communities are proposed to catalyse a range of useful reactions. Unlike bioanodes, model biocathode organisms have not yet been successfully cultivated in isolation highlighting the need for culture‐independent approaches to characterization. Biocathode MCL (Marinobacter, Chromatiaceae, Labrenzia) is a microbial community proposed to couple CO2 fixation to extracellular electron transfer and O2 reduction. Previous metagenomic analysis of a single MCL bioelectrochemical system (BES) resulted in resolution of 16 bin genomes. To further resolve bin genomes and compare community composition across replicate MCL BES, we performed shotgun metagenomic and 16S rRNA gene (16S) sequencing at steady‐state current. Clustering pooled reads from replicate BES increased the number of resolved bin genomes to 20, over half of which were > 90% complete. Direct comparison of unassembled metagenomic reads and 16S operational taxonomic units (OTUs) predicted higher community diversity than the assembled/clustered metagenome and the predicted relative abundances did not match. However, when 16S OTUs were mapped to bin genomes and genome abundance was scaled by 16S gene copy number, estimated relative abundance was more similar to metagenomic analysis. The relative abundance of the bin genome representing ‘Ca. Tenderia electrophaga’ was correlated with increasing current, further supporting the hypothesis that this organism is the electroautotroph.
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Affiliation(s)
- Anthony P Malanoski
- United States Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC, 20375, USA
| | - Baochuan Lin
- Defense Threat Reduction Agency, 8725 John J Kingman Rd #6201, Fort Belvoir, VA, 22060, USA
| | - Brian J Eddie
- United States Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC, 20375, USA
| | - Zheng Wang
- United States Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC, 20375, USA
| | - W Judson Hervey
- United States Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC, 20375, USA
| | - Sarah M Glaven
- United States Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC, 20375, USA
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