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Hou L, Zheng B, Jiang Z, Hu Y, Shi L, Dong Y, Jiang Y. The dmsEFABGH operon encodes an essential and modular electron transfer pathway for extracellular iodate reduction by Shewanella oneidensis MR-1. Microbiol Spectr 2024:e0051224. [PMID: 38916364 DOI: 10.1128/spectrum.00512-24] [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: 02/27/2024] [Accepted: 06/03/2024] [Indexed: 06/26/2024] Open
Abstract
Extracellular iodate reduction by Shewanella spp. contributes to iodide generation in the biogeochemical cycling of iodine. However, there is a disagreement on whether Shewanella spp. use different extracellular electron transfer pathways with dependence on electron donors in iodate reduction. In this study, a series of gene deletion mutants of Shewanella oneidensis MR-1 were created to investigate the roles of dmsEFABGH, mtrCAB, and so4357-so4362 operons in iodate reduction. The iodate-reducing activity of the mutants was tested with lactate, formate, and H2 as the sole electron donors, respectively. In the absence of single-dms gene, iodate reduction efficiency of the mutants was only 12.9%-84.0% with lactate at 24 hours, 22.1%-85.9% with formate at 20 hours, and 19.6%-57.7% with H2 at 42 hours in comparison to complete reduction by the wild type. Progressive inhibition of iodate reduction was observed when the dms homolog from the so4357-so4362 operon was deleted in the single-dms gene mutants. This result revealed complementation of dmsEFABGH by so4357-so4362 at the single-gene level, indicating modularity of the extracellular electron transfer pathway encoded by dmsEFABGH operon. Under the conditions of all electron donors, significant inhibition of iodate reduction and accumulation of H2O2 were detected for ΔmtrCAB. Collectively, these results demonstrated that the dmsEFABGH operon encodes an essential and modular iodate-reducing pathway without electron donor dependence in S. oneidensis MR-1. The mtrCAB operon was involved in H2O2 elimination with all electron donors. The findings in this study improved the understanding of molecular mechanisms underlying extracellular iodate reduction.IMPORTANCEIodine is an essential trace element for human and animals. Recent studies revealed the contribution of microbial extracellular reduction of iodate in biogeochemical cycling of iodine. Multiple reduced substances can be utilized by microorganisms as energy source for iodate reduction. However, varied electron transfer pathways were proposed for iodate reduction with different electron donors in the model strain Shewanella oneidensis MR-1. Here, through a series of gene deletion and iodate reduction experiments, we discovered that the dmsEFABGH operon was essential for iodate reduction with at least three electron donors, including lactate, formate, and H2. The so4357-so4362 operon was first demonstrated to be capable of complementing the function of dmsEFABGH at single-gene level.
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Affiliation(s)
- Lingyu Hou
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
| | - Beiling Zheng
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
| | - Zhou Jiang
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
| | - Yidan Hu
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
| | - Liang Shi
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei, China
| | - Yiran Dong
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei, China
| | - Yongguang Jiang
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geosciences, Wuhan, Hubei, China
- Hubei Key Laboratory of Wetland Evolution & Eco-Restoration, Wuhan, Hubei, China
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Zhang J, Li F, Liu D, Liu Q, Song H. Engineering extracellular electron transfer pathways of electroactive microorganisms by synthetic biology for energy and chemicals production. Chem Soc Rev 2024; 53:1375-1446. [PMID: 38117181 DOI: 10.1039/d3cs00537b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The excessive consumption of fossil fuels causes massive emission of CO2, leading to climate deterioration and environmental pollution. The development of substitutes and sustainable energy sources to replace fossil fuels has become a worldwide priority. Bio-electrochemical systems (BESs), employing redox reactions of electroactive microorganisms (EAMs) on electrodes to achieve a meritorious combination of biocatalysis and electrocatalysis, provide a green and sustainable alternative approach for bioremediation, CO2 fixation, and energy and chemicals production. EAMs, including exoelectrogens and electrotrophs, perform extracellular electron transfer (EET) (i.e., outward and inward EET), respectively, to exchange energy with the environment, whose rate determines the efficiency and performance of BESs. Therefore, we review the synthetic biology strategies developed in the last decade for engineering EAMs to enhance the EET rate in cell-electrode interfaces for facilitating the production of electricity energy and value-added chemicals, which include (1) progress in genetic manipulation and editing tools to achieve the efficient regulation of gene expression, knockout, and knockdown of EAMs; (2) synthetic biological engineering strategies to enhance the outward EET of exoelectrogens to anodes for electricity power production and anodic electro-fermentation (AEF) for chemicals production, including (i) broadening and strengthening substrate utilization, (ii) increasing the intracellular releasable reducing equivalents, (iii) optimizing c-type cytochrome (c-Cyts) expression and maturation, (iv) enhancing conductive nanowire biosynthesis and modification, (v) promoting electron shuttle biosynthesis, secretion, and immobilization, (vi) engineering global regulators to promote EET rate, (vii) facilitating biofilm formation, and (viii) constructing cell-material hybrids; (3) the mechanisms of inward EET, CO2 fixation pathway, and engineering strategies for improving the inward EET of electrotrophic cells for CO2 reduction and chemical production, including (i) programming metabolic pathways of electrotrophs, (ii) rewiring bioelectrical circuits for enhancing inward EET, and (iii) constructing microbial (photo)electrosynthesis by cell-material hybridization; (4) perspectives on future challenges and opportunities for engineering EET to develop highly efficient BESs for sustainable energy and chemical production. We expect that this review will provide a theoretical basis for the future development of BESs in energy harvesting, CO2 fixation, and chemical synthesis.
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Affiliation(s)
- Junqi Zhang
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Feng Li
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Dingyuan Liu
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Qijing Liu
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
| | - Hao Song
- Frontier Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, and School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
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Li Y, Liu G, Shi H. Expansion of carbon source utilization range of Shewanella oneidensis for efficient azo dye wastewater treatment through co-culture with Lactobacillus plantarum. Arch Microbiol 2023; 205:297. [PMID: 37490061 DOI: 10.1007/s00203-023-03634-5] [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: 05/15/2023] [Revised: 06/15/2023] [Accepted: 07/10/2023] [Indexed: 07/26/2023]
Abstract
Shewanella oneidensis has demonstrated excellent potential for azo dye decolorization and degradation. However, in anaerobic environments, S. oneidensis has a narrow carbon source spectrum, which requires additional electron donors, such as sodium lactate. This increases the practical application costs for wastewater treatment. Here, we aimed to expand the carbon source utilization range of S. oneidensis FJAT-2478 by co-culturing it with Lactobacillus plantarum FJAT-7926, leveraging their commensalism relationship to develop a metabolic chain. Results showed that a 1:2 initial ratio of L. plantarum FJAT-7926 to S. oneidensis FJAT-2478 achieved a 97.16% decolorization rate of methyl orange when glucose served as the sole carbon source. This co-culture system achieved a decolorization rate comparable to that obtained using sodium lactate as an electron donor and was significantly higher than that achieved by L. plantarum FJAT-7926 (7.88%) or S. oneidensis FJAT-2478 (6.89%) alone. After undergoing five cycles, the co-culture system continued to exhibit effective decolorization. It was demonstrated that the co-culture system could use common and inexpensive carbon sources, such as starch, molasses, sucrose, and maltose, to decolorize azo dyes. For instance, 100 mg/L methyl orange could be degraded by over 98.05% within 24 h. The results indicated that the degradation rates of methyl orange were higher when L. plantarum was inoculated first, followed by a subsequent inoculation of S. oneidensis after 2 h. The co-culturing of L. plantarum FJAT-7926 and S. oneidensis FJAT-2478 proved to be an effective strategy in treating azo dye wastewater, expanding the potential practical applications of S. oneidensis.
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Affiliation(s)
- Yanbo Li
- Department of Biotechnology, Fujian Vocational College of Agriculture, Fuzhou, Fujian, 350119, People's Republic of China
| | - Guohong Liu
- Agricultural Bio-resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, 350003, People's Republic of China
| | - Huai Shi
- Agricultural Bio-resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, 350003, People's Republic of China.
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Bertling K, Banerjee A, Saffarini D. Aerobic Respiration and Its Regulation in the Metal Reducer Shewanella oneidensis. Front Microbiol 2021; 12:723835. [PMID: 34566926 PMCID: PMC8458880 DOI: 10.3389/fmicb.2021.723835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 07/26/2021] [Indexed: 11/23/2022] Open
Abstract
Shewanella oneidensis MR-1 is a facultative anaerobe known for its ability to reduce metal oxides. Anaerobic respiration, especially metal reduction, has been the subject of extensive research. In contrast, S. oneidensis aerobic respiration has received less attention. S. oneidensis expresses cbb3- and aa3-type cytochrome c oxidases and a bd-type quinol oxidase. The aa3-type oxidase, which in other bacteria is the major oxygen reductase under oxygen replete conditions, does not appear to contribute to aerobic respiration and growth in S. oneidensis. Our results indicated that although the aa3-type oxidase does not play a role in aerobic growth on lactate, the preferred carbon source for S. oneidensis, it is involved in growth on pyruvate or acetate. These results highlight the importance of testing multiple carbon and energy sources when attempting to identify enzyme activities and mutant phenotypes. Several regulatory proteins contribute to the regulation of aerobic growth in S. oneidensis including CRP and ArcA. The 3',5'-cAMP phosphodiesterase (CpdA) appears to play a more significant role in aerobic growth than either CRP or ArcA, yet the deficiency does not appear to be the result of reduced oxidase genes expression. Interestingly, the ∆cpdA mutant was more deficient in aerobic respiration with several carbon sources tested compared to ∆crp, which was moderately deficient only in the presence of lactate. To identify the reason for ∆cpdA aerobic growth deficiency, we isolated a suppressor mutant with transposon insertion in SO_3550. Inactivation of this gene, which encodes an anti-sigma factor, restored aerobic growth in the cpdA mutant to wild-type levels. Inactivation of SO_3550 in wild-type cells, however, did not affect aerobic growth. The S. oneidensis genome encodes two additional CRP-like proteins that we designated CrpB and CrpC. Mutants that lack crpB and crpC were deficient in aerobic growth, but this deficiency was not due to the loss of oxidase gene expression.
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Affiliation(s)
- Kristen Bertling
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Areen Banerjee
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
| | - Daad Saffarini
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, United States
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Shewanella oneidensis MR-1 as a bacterial platform for electro-biotechnology. Essays Biochem 2021; 65:355-364. [PMID: 33769488 PMCID: PMC8314016 DOI: 10.1042/ebc20200178] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 03/16/2021] [Accepted: 03/18/2021] [Indexed: 12/18/2022]
Abstract
The genus Shewanella comprises over 70 species of heterotrophic bacteria with versatile respiratory capacities. Some of these bacteria are known to be pathogens of fishes and animals, while many are non-pathogens considered to play important roles in the global carbon cycle. A representative strain is Shewanella oneidensis MR-1 that has been intensively studied for its ability to respire diverse electron acceptors, such as oxygen, nitrate, sulfur compounds, metals, and organics. In addition, studies have been focused on its ability as an electrochemically active bacterium that is capable of discharging electrons to and receiving electrons from electrodes in bioelectrochemical systems (BESs) for balancing intracellular redox states. This ability is expected to be applied to electro-fermentation (EF) for producing value-added chemicals that conventional fermentation technologies are difficult to produce efficiently. Researchers are also attempting to utilize its electrochemical ability for controlling gene expression, for which electro-genetics (EG) has been coined. Here we review fundamental knowledge on this bacterium and discuss future directions of studies on its applications to electro-biotechnology (EB).
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Kouzuma A. Molecular mechanisms regulating the catabolic and electrochemical activities of Shewanella oneidensis MR-1. Biosci Biotechnol Biochem 2021; 85:1572-1581. [PMID: 33998649 DOI: 10.1093/bbb/zbab088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 04/17/2021] [Indexed: 11/14/2022]
Abstract
Electrochemically active bacteria (EAB) interact electrochemically with electrodes via extracellular electron transfer (EET) pathways. These bacteria have attracted significant attention due to their utility in environmental-friendly bioelectrochemical systems (BESs), including microbial fuel cells and electrofermentation systems. The electrochemical activity of EAB is dependent on their carbon catabolism and respiration; thus, understanding how these processes are regulated will provide insights into the development of a more efficient BES. The process of biofilm formation by EAB on BES electrodes is also important for electric current generation because it facilitates physical and electrochemical interactions between EAB cells and electrodes. This article summarizes the current knowledge on EET-related metabolic and cellular functions of a model EAB, Shewanella oneidensis MR-1, focusing specifically on regulatory systems for carbon catabolism, EET pathways, and biofilm formation. Based on recent developments, the author also discusses potential uses of engineered S. oneidensis strains for various biotechnological applications.
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Affiliation(s)
- Atsushi Kouzuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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Hirose A, Kouzuma A, Watanabe K. Towards development of electrogenetics using electrochemically active bacteria. Biotechnol Adv 2019; 37:107351. [DOI: 10.1016/j.biotechadv.2019.02.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/09/2019] [Accepted: 02/15/2019] [Indexed: 12/20/2022]
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Singh K, Ainala SK, Kim Y, Park S. A novel D(-)-lactic acid-inducible promoter regulated by the GntR-family protein D-LldR of Pseudomonas fluorescens. Synth Syst Biotechnol 2019; 4:157-164. [PMID: 31517075 PMCID: PMC6731338 DOI: 10.1016/j.synbio.2019.08.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 08/23/2019] [Accepted: 08/26/2019] [Indexed: 11/26/2022] Open
Abstract
Lactic acid has two stereoisomers of D(-)- and L(+)-forms, both of which are important monomers of biodegradable plastic, poly-lactic acid. In this study, a novel d-lactate inducible system was identified in Pseudomonas fluorescens A506, partially characterized and tested as biosensor. The d-lactate catabolic operon (lldP-dld-II) was negatively regulated through the inversely transcribed D-lldR (encoding a GntR-type regulator), where the repression is relieved by addition of d-lactate. The derepression was specific to d-lactate and marginally affected by l-lactate. The D-LldR-responsive operator, showing dyad symmetry and separated by one base, was located between +11 and + 27 from the transcription start site of the lldP-dld-II operon. By site-directed mutagenesis, a motif with a dyad symmetry (AATTGGTAtTACCAATT), present in the upstream region of lldP, was identified as essential for the binding of LldR. d-lactate biosensors were developed by connecting the upregulation by d-lactate to a green fluorescent readout. About ~6.0-fold induction by 100 mM d-lactate was observed compared to l-lactate.
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Affiliation(s)
- Kalpana Singh
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Republic of Korea
| | - Satish Kumar Ainala
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Republic of Korea
| | - Yeonhee Kim
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Republic of Korea
- School of Chemical and Biomolecular Engineering, Pusan National University, Busan, 46241, Republic of Korea
| | - Sunghoon Park
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, Republic of Korea
- School of Chemical and Biomolecular Engineering, Pusan National University, Busan, 46241, Republic of Korea
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Kasai T, Tomioka Y, Kouzuma A, Watanabe K. Overexpression of the adenylate cyclase gene cyaC facilitates current generation by Shewanella oneidensis in bioelectrochemical systems. Bioelectrochemistry 2019; 129:100-105. [PMID: 31153124 DOI: 10.1016/j.bioelechem.2019.05.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/18/2019] [Accepted: 05/19/2019] [Indexed: 12/26/2022]
Abstract
Electrochemically active bacteria (EAB) are capable of electrochemical interactions with electrodes via extracellular electron transfer (EET) pathways and serve as essential components in bioelectrochemical systems. Previous studies have suggested that EAB, such as Shewanella oneidensis MR-1, use cyclic AMP (cAMP) receptor proteins to coordinately regulate the expression of catabolic and EET-related genes, prompting us to hypothesize that the intracellular cAMP concentration is an important factor determining the electrochemical activities of EAB. The present study constructed an MR-1 mutant, cyaC-OE, that overexpressed cyaC, a gene encoding a membrane-bound class III adenylate cyclase, and examined its electrochemical and transcriptomic characteristics. We show that the intracellular cAMP concentration in cyaC-OE is more than five times that in wild-type MR-1, and that cya-OE generates approximately two-fold higher current in BES than the wild-type strain. In addition, the expression of genes involved in EET and anaerobic carbon catabolism is up-regulated in cya-OE compared to that in the wild-type strain. These results suggest that increasing the intracellular cAMP level is a promising approach for constructing EAB with high catabolic and electrochemical activities.
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Affiliation(s)
- Takuya Kasai
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Yuki Tomioka
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Atsushi Kouzuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
| | - Kazuya Watanabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
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Hirose A, Kasai T, Koga R, Suzuki Y, Kouzuma A, Watanabe K. Understanding and engineering electrochemically active bacteria for sustainable biotechnology. BIORESOUR BIOPROCESS 2019. [DOI: 10.1186/s40643-019-0245-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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Roles of d-Lactate Dehydrogenases in the Anaerobic Growth of Shewanella oneidensis MR-1 on Sugars. Appl Environ Microbiol 2019; 85:AEM.02668-18. [PMID: 30504209 DOI: 10.1128/aem.02668-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 11/18/2018] [Indexed: 11/20/2022] Open
Abstract
Shewanella oneidensis MR-1 is a facultative anaerobe that respires using a variety of electron acceptors. Although this organism is incapable of fermentative growth in the absence of electron acceptors, its genome encodes LdhA (a putative fermentative NADH-dependent d-lactate dehydrogenase [d-LDH]) and Dld (a respiratory quinone-dependent d-LDH). However, the physiological roles of LdhA in MR-1 are unclear. Here, we examined the activity, transcriptional regulation, and traits of deletion mutants to gain insight into the roles of LdhA in the anaerobic growth of MR-1. Analyses of d-LDH activity in MR-1 and the ldhA deletion mutant confirmed that LdhA functions as an NADH-dependent d-LDH that catalyzes the reduction of pyruvate to d-lactate. In vivo and in vitro assays revealed that ldhA expression was positively regulated by the cyclic-AMP receptor protein, a global transcription factor that regulates anaerobic respiratory pathways in MR-1, suggesting that LdhA functions in coordination with anaerobic respiration. Notably, we found that a deletion mutant of all four NADH dehydrogenases (NDHs) in MR-1 (ΔNDH mutant) retained the ability to grow on N-acetylglucosamine under fumarate-respiring conditions, while an additional deletion of ldhA or dld deprived the ΔNDH mutant of this growth ability. These results indicate that LdhA-Dld serves as a bypass of NDH in electron transfer from NADH to quinones. Our findings suggest that the LdhA-Dld system manages intracellular redox balance by utilizing d-lactate as a temporal electron sink under electron acceptor-limited conditions.IMPORTANCE NADH-dependent LDHs are conserved among diverse organisms and contribute to NAD+ regeneration in lactic acid fermentation. However, this type of LDH is also present in nonfermentative bacteria, including members of the genus Shewanella, while their physiological roles in these bacteria remain unknown. Here, we show that LdhA (an NADH-dependent d-LDH) works in concert with Dld (a quinone-dependent d-LDH) to transfer electrons from NADH to quinones during sugar catabolism in S. oneidensis MR-1. Our results indicate that d-lactate acts as an intracellular electron mediator to transfer electrons from NADH to membrane quinones. In addition, d-lactate serves as a temporal electron sink when respiratory electron acceptors are not available. Our study suggests novel physiological roles for d-LDHs in providing nonfermentative bacteria with catabolic flexibility under electron acceptor-limited conditions.
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Beblawy S, Bursac T, Paquete C, Louro R, Clarke TA, Gescher J. Extracellular reduction of solid electron acceptors by Shewanella oneidensis. Mol Microbiol 2018; 109:571-583. [PMID: 29995975 DOI: 10.1111/mmi.14067] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2018] [Indexed: 12/11/2022]
Abstract
Shewanella oneidensis is the best understood model organism for the study of dissimilatory iron reduction. This review focuses on the current state of our knowledge regarding this extracellular respiratory process and highlights its physiologic, regulatory and biochemical requirements. It seems that we have widely understood how respiratory electrons can reach the cell surface and what the minimal set of electron transport proteins to the cell surface is. Nevertheless, even after decades of work in different research groups around the globe there are still several important questions that were not answered yet. In particular, the physiology of this organism, the possible evolutionary benefit of some responses to anoxic conditions, as well as the exact mechanism of electron transfer onto solid electron acceptors are yet to be addressed. The elucidation of these questions will be a great challenge for future work and important for the application of extracellular respiration in biotechnological processes.
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Affiliation(s)
- Sebastian Beblawy
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany
| | - Thea Bursac
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany
| | - Catarina Paquete
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, Oeiras, 2780-157, Portugal
| | - Ricardo Louro
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, Oeiras, 2780-157, Portugal
| | - Thomas A Clarke
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Johannes Gescher
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany.,Institute for Biological Interfaces, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
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Ueoka N, Kouzuma A, Watanabe K. Electrode plate-culture methods for colony isolation of exoelectrogens from anode microbiomes. Bioelectrochemistry 2018; 124:1-6. [PMID: 29990596 DOI: 10.1016/j.bioelechem.2018.06.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 06/19/2018] [Accepted: 06/19/2018] [Indexed: 11/17/2022]
Abstract
Exoelectrogens play central roles in microbial fuel cells and other bioelectrochemical systems (BESs), yet their physiological diversity remains largely elusive due to the lack of efficient methods for the isolation from naturally occurring microbiomes. The present study developed an electrode plate-culture (EPC) method that facilitates selective colony formation by exoelectrogens and used it for isolating them from an exoelectrogenic microbiome enriched from paddy-field soil. In an EPC device, the surface of solidified agarose medium was spread with a suspension of a microbiome and covered with a transparent fluorine doped tin oxide (FTO) electrode (poised at 0 V vs. the standard hydrogen electrode) that served as the sole electron acceptor. The medium contained acetate as the major growth substrate and Coomassie Brilliant Blue as a dye for visualizing colonies under FTO. It was shown that colonies successfully appeared under FTO in association with current generation. Analyses of 16S rRNA gene sequences of colonies indicated that they were affiliated with genera Citrobacter, Geobacter and others. Among them, Citrobacter and Geobacter isolates were found to be exoelectrogenic in pure-culture BESs. These results demonstrate the utility of the EPC method for colony isolation of exoelectrogens.
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Affiliation(s)
- N Ueoka
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, 192-0392 Tokyo, Japan
| | - A Kouzuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, 192-0392 Tokyo, Japan
| | - K Watanabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, 192-0392 Tokyo, Japan.
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Hirose A, Kasai T, Aoki M, Umemura T, Watanabe K, Kouzuma A. Electrochemically active bacteria sense electrode potentials for regulating catabolic pathways. Nat Commun 2018; 9:1083. [PMID: 29540717 PMCID: PMC5852097 DOI: 10.1038/s41467-018-03416-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 02/09/2018] [Indexed: 01/08/2023] Open
Abstract
Electrochemically active bacteria (EAB) receive considerable attention for their utility in bioelectrochemical processes. Although electrode potentials are known to affect the metabolic activity of EAB, it is unclear whether EAB are able to sense and respond to electrode potentials. Here, we show that, in the presence of a high-potential electrode, a model EAB Shewanella oneidensis MR-1 can utilize NADH-dependent catabolic pathways and a background formate-dependent pathway to achieve high growth yield. We also show that an Arc regulatory system is involved in sensing electrode potentials and regulating the expression of catabolic genes, including those for NADH dehydrogenase. We suggest that these findings may facilitate the use of EAB in biotechnological processes and offer the molecular bases for their ecological strategies in natural habitats.
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Affiliation(s)
- Atsumi Hirose
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Takuya Kasai
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Motohide Aoki
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Tomonari Umemura
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Kazuya Watanabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan
| | - Atsushi Kouzuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
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