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Ahmadi F, Lackner M. Recent findings in methanotrophs: genetics, molecular ecology, and biopotential. Appl Microbiol Biotechnol 2024; 108:60. [PMID: 38183483 DOI: 10.1007/s00253-023-12978-3] [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: 08/30/2023] [Revised: 09/08/2023] [Accepted: 10/01/2023] [Indexed: 01/08/2024]
Abstract
The potential consequences for mankind could be disastrous due to global warming, which arises from an increase in the average temperature on Earth. The elevation in temperature primarily stems from the escalation in the concentration of greenhouse gases (GHG) such as CO2, CH4, and N2O within the atmosphere. Among these gases, methane (CH4) is particularly significant in driving alterations to the worldwide climate. Methanotrophic bacteria possess the distinctive ability to employ methane as both as source of carbon and energy. These bacteria show great potential as exceptional biocatalysts in advancing C1 bioconversion technology. The present review describes recent findings in methanotrophs including aerobic and anaerobic methanotroph bacteria, phenotypic characteristics, biotechnological potential, their physiology, ecology, and native multi-carbon utilizing pathways, and their molecular biology. The existing understanding of methanogenesis and methanotrophy in soil, as well as anaerobic methane oxidation and methanotrophy in temperate and extreme environments, is also covered in this discussion. New types of methanogens and communities of methanotrophic bacteria have been identified from various ecosystems and thoroughly examined for a range of biotechnological uses. Grasping the processes of methanogenesis and methanotrophy holds significant importance in the development of innovative agricultural techniques and industrial procedures that contribute to a more favorable equilibrium of GHG. This current review centers on the diversity of emerging methanogen and methanotroph species and their effects on the environment. By amalgamating advanced genetic analysis with ecological insights, this study pioneers a holistic approach to unraveling the biopotential of methanotrophs, offering unprecedented avenues for biotechnological applications. KEY POINTS: • The physiology of methanotrophic bacteria is fundamentally determined. • Native multi-carbon utilizing pathways in methanotrophic bacteria are summarized. • The genes responsible for encoding methane monooxygenase are discussed.
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Affiliation(s)
- Fatemeh Ahmadi
- School of Agriculture and Environment, University of Western Australia, Crawley, 6009, Australia
- Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, 7001, Australia
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Xie F, Yuan Q, Meng Y, Luan F. Degradation of methylmercury into Hg(0) by the oxidation of iron(II) minerals. WATER RESEARCH 2024; 256:121645. [PMID: 38653093 DOI: 10.1016/j.watres.2024.121645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 03/25/2024] [Accepted: 04/18/2024] [Indexed: 04/25/2024]
Abstract
Mercury contamination is a global concern, and the degradation and detoxification of methylmercury have gained significant attention due to its neurotoxicity and biomagnification within the food chain. However, the currently known pathways of abiotic demethylation are limited to light-induced photodegradation process and little is known about light-independent abiotic demethylation of methylmercury. In this study, we reported a novel abiotic pathway for the degradation of methylmercury through the oxidation of both mineral structural iron(II) and surface-adsorbed iron(II) in the absence of light. Our findings reveal that methylmercury can be oxidatively degraded by reactive oxygen species, specifically hydroxyl and superoxide radicals, which are generated from the oxidation of iron(II) minerals under dark conditions. Surprisingly, Hg(0) trapping experiments demonstrated that inorganic Hg(II) resulting from the oxidative degradation of methylmercury was rapidly reduced to gaseous Hg(0) by iron(II) minerals. The demethylation of methylmercury, coupled with the generation of Hg(0), suggests a potential natural attenuation process for methylmercury. Our results highlight the underappreciated roles of iron(II) minerals in the abiotic degradation of methylmercury and the release of gaseous Hg(0) into the atmosphere.
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Affiliation(s)
- Fuyu Xie
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Qingke Yuan
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China
| | - Ying Meng
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China.
| | - Fubo Luan
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
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Yu C, Peng M, Wang X, Pan X. Photochemical demethylation of methylmercury (MeHg) in aquatic systems: A review of MeHg species, mechanisms, and influencing factors. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 344:123297. [PMID: 38195023 DOI: 10.1016/j.envpol.2024.123297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/01/2023] [Accepted: 01/02/2024] [Indexed: 01/11/2024]
Abstract
Photodemethylation is the major pathway of methylmercury (MeHg) demethylation in surface water before uptake by the food chain, whose mechanisms and influence factors are still not completely understood. Here, we review the current knowledge on photodemethylation of MeHg and divide MeHg photolysis into three pathways: (1) direct photodemethylation, (2) free radical attack, and (3) intramolecular electron or energy transfer. In aquatic environments, dissolved organic matter is involved into all above pathways, and due to its complex compositions, properties and concentrations, DOM poses multiple functions during the PD of MeHg. DOM-MeHg complex (mainly by sulfur-containing molecules) might weaken the C-Hg bond and enhance PD through both direct and indirect pathways. In special, synergistic effects of both strong binding sites and chromophoric moieties in DOM might lead to intramolecular electron or energy transfer. Moreover, DOM might play a role of radical scavenger; while triplet state DOM, which is generated by chromophoric DOM under light, might become a source of free radicals. Apart from DOMs, transition metals, halides, NO3-, NO2-, and carbonates also act as radical initialaters or scavengers, and significantly pose effects on radical demethylation, which is generally mediated by hydroxyl radicals and singlet oxygen. Environmental factors such as pH, light wavelength, light intensity, dissolved oxygen, salinity, and suspended particles also affect the PD of MeHg. This study assessed previously published works on three major mechanisms, with the goal of providing general estimates for photodemethylation under various environment factors according to know effects, and highlighting the current uncertainties for future research directions.
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Affiliation(s)
- Chenghao Yu
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Mao Peng
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xiaonan Wang
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xiangliang Pan
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
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Hao Z, Zhao L, Liu J, Pu Q, Chen J, Meng B, Feng X. Relative importance of aceticlastic methanogens and hydrogenotrophic methanogens on mercury methylation and methylmercury demethylation in paddy soils. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167601. [PMID: 37832685 DOI: 10.1016/j.scitotenv.2023.167601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 09/28/2023] [Accepted: 10/03/2023] [Indexed: 10/15/2023]
Abstract
The accumulation of methylmercury (MeHg) in paddy soil results from a subtle balance between inorganic mercury (e.g., HgII) methylation and MeHg demethylation. Methanogens not only act as Hg methylators but may also facilitate MeHg demethylation. However, the diverse methanogen flora (e.g., aceticlastic and hydrogenotrophic types) that exists under ambient conditions has not previously been considered. Accordingly, the roles of different types of methanogens in HgII methylation and MeHg degradation in paddy soils were studied using the Hg isotope tracing technique combined with the application of methanogen inhibitors/stimulants. It was found that the response of HgII methylation to methanogen inhibitors or stimulants was site-dependent. Specifically, aceticlastic methanogens were suggested as the potential HgII methylators at the low Hg level background site, whereas hydrogenotrophic methanogens were potentially involved in MeHg production as Hg levels increased. In contrast, both aceticlastic and hydrogenotrophic methanogens facilitated MeHg degradation across the sampling sites. Additionally, competition between hydrogenotrophic and aceticlastic methanogens was observed in Hg-polluted paddy soils, implying that net MeHg production could be alleviated by promoting aceticlastic methanogens or inhibiting hydrogenotrophic methanogens. The findings gained from this study improve the understanding of the role of methanogens in net MeHg formation and link carbon turnover to Hg biogeochemistry in rice paddy ecosystems.
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Affiliation(s)
- Zhengdong Hao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Zhao
- School of Management Science, Guizhou University of Finance and Economics, Guiyang 550025, China; Guizhou Key Laboratory of Big Data Statistical Analysis (No. [2019]5103), Guiyang 550025, China.
| | - Jiang Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Qiang Pu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Ji Chen
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
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Zhang L, Sun X, Wang L, Zhang H, Chu H, Li Y. Soil edaphic factors and climate seasonality explain the turnover of methanotrophic communities in riparian wetlands. ENVIRONMENTAL RESEARCH 2023; 233:116447. [PMID: 37331554 DOI: 10.1016/j.envres.2023.116447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 06/08/2023] [Accepted: 06/16/2023] [Indexed: 06/20/2023]
Abstract
Aerobic CH4-oxidizing bacteria (methanotrophs) represent a biological model system for the removal of atmospheric CH4, which is sensitive to the dynamics of water tables. However, little attention has been given to the turnover of methanotrophic communities across wet and dry periods in riparian wetlands. Here, by sequencing the pmoA gene, we investigated the turnover of soil methanotrophic communities across wet and dry periods in typical riparian wetlands that experience intensive agricultural practices. The results demonstrated that the methanotrophic abundance and diversity were significantly higher in the wet period than in the dry period, probably owing to the climatic seasonal succession and associated variation in soil edaphic factors. The co-occurrence patterns of the interspecies association analysis demonstrated that the key ecological clusters (i.e., Mod#1, Mod#2, Mod#4, Mod#5) showed contrasting correlations with soil edaphic properties between wet and dry periods. The linear regression slope of the relationships between the relative abundance of Mod#1 and the carbon to nitrogen ratio was higher in the wet period than in the dry period, whereas the linear regression slope of the relationships between the relative abundance of Mod#2 and soil nitrogen content (i.e., dissolved organic nitrogen, nitrate, and total nitrogen) was higher in the dry period than in the wet period. Moreover, Stegen's null model combined with phylogenetic group-based assembly analysis demonstrated that the methanotrophic community exhibited a higher proportion of drift (55.0%) and a lower contribution of dispersal limitation (24.5%) in the wet period than in the dry period (43.8% and 35.7%, respectively). Overall, these findings demonstrate that the turnover of methanotrophic communities across wet and dry periods were soil edaphic factors and climate dependent.
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Affiliation(s)
- Liyan Zhang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, China
| | - Xiangxin Sun
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Longfei Wang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, China
| | - Huanjun Zhang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, China
| | - Haiyan Chu
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yi Li
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, China.
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Zhang R, Aris-Brosou S, Storck V, Liu J, Abdelhafiz MA, Feng X, Meng B, Poulain AJ. Mining-impacted rice paddies select for Archaeal methylators and reveal a putative (Archaeal) regulator of mercury methylation. ISME COMMUNICATIONS 2023; 3:74. [PMID: 37454192 PMCID: PMC10349881 DOI: 10.1038/s43705-023-00277-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 06/19/2023] [Accepted: 06/22/2023] [Indexed: 07/18/2023]
Abstract
Methylmercury (MeHg) is a microbially produced neurotoxin derived from inorganic mercury (Hg), which accumulation in rice represents a major health concern to humans. However, the microbial control of MeHg dynamics in the environment remains elusive. Here, leveraging three rice paddy fields with distinct concentrations of Hg (Total Hg (THg): 0.21-513 mg kg-1 dry wt. soil; MeHg: 1.21-6.82 ng g-1 dry wt. soil), we resorted to metagenomics to determine the microbial determinants involved in MeHg production under contrasted contamination settings. We show that Hg methylating Archaea, along with methane-cycling genes, were enriched in severely contaminated paddy soils. Metagenome-resolved Genomes of novel putative Hg methylators belonging to Nitrospinota (UBA7883), with poorly resolved taxonomy despite high completeness, showed evidence of facultative anaerobic metabolism and adaptations to fluctuating redox potential. Furthermore, we found evidence of environmental filtering effects that influenced the phylogenies of not only hgcA genes under different THg concentrations, but also of two housekeeping genes, rpoB and glnA, highlighting the need for further experimental validation of whether THg drives the evolution of hgcAB. Finally, assessment of the genomic environment surrounding hgcAB suggests that this gene pair may be regulated by an archaeal toxin-antitoxin (TA) system, instead of the more frequently found arsR-like genes in bacterial methylators. This suggests the presence of distinct hgcAB regulation systems in bacteria and archaea. Our results support the emerging role of Archaea in MeHg cycling under mining-impacted environments and shed light on the differential control of the expression of genes involved in MeHg formation between Archaea and Bacteria.
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Affiliation(s)
- Rui Zhang
- Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Stéphane Aris-Brosou
- Department of Biology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
- Department of Mathematics and Statistics, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Veronika Storck
- Department of Civil Engineering, Polytechnique Montréal, Montréal, QC, H3C 3A7, Canada
| | - Jiang Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Mahmoud A Abdelhafiz
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China.
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Einer C, Munk DE, Park E, Akdogan B, Nagel J, Lichtmannegger J, Eberhagen C, Rieder T, Vendelbo MH, Michalke B, Wimmer R, Blutke A, Feuchtinger A, Dershwitz P, DiSpirito AM, Islam T, Castro RE, Min BK, Kim T, Choi S, Kim D, Jung C, Lee H, Park D, Im W, Eun SY, Cho YH, Semrau JD, Rodrigues CMP, Hohenester S, Damgaard Sandahl T, DiSpirito AA, Zischka H. ARBM101 (Methanobactin SB2) Drains Excess Liver Copper via Biliary Excretion in Wilson's Disease Rats. Gastroenterology 2023; 165:187-200.e7. [PMID: 36966941 DOI: 10.1053/j.gastro.2023.03.216] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 03/03/2023] [Accepted: 03/08/2023] [Indexed: 04/22/2023]
Abstract
BACKGROUND & AIMS Excess copper causes hepatocyte death in hereditary Wilson's disease (WD). Current WD treatments by copper-binding chelators may gradually reduce copper overload; they fail, however, to bring hepatic copper close to normal physiological levels. Consequently, lifelong daily dose regimens are required to hinder disease progression. This may result in severe issues due to nonadherence or unwanted adverse drug reactions and also due to drug switching and ultimate treatment failures. This study comparatively tested bacteria-derived copper binding agents-methanobactins (MBs)-for efficient liver copper depletion in WD rats as well as their safety and effect duration. METHODS Copper chelators were tested in vitro and in vivo in WD rats. Metabolic cage housing allowed the accurate assessment of animal copper balances and long-term experiments related to the determination of minimal treatment phases. RESULTS We found that copper-binding ARBM101 (previously known as MB-SB2) depletes WD rat liver copper dose dependently via fecal excretion down to normal physiological levels within 8 days, superseding the need for continuous treatment. Consequently, we developed a new treatment consisting of repetitive cycles, each of ∼1 week of ARBM101 applications, followed by months of in-between treatment pauses to ensure a healthy long-term survival in WD rats. CONCLUSIONS ARBM101 safely and efficiently depletes excess liver copper from WD rats, thus allowing for short treatment periods as well as prolonged in-between rest periods.
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Affiliation(s)
- Claudia Einer
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Ditte Emilie Munk
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark
| | - Eok Park
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea; Department of Pharmacy, College of Pharmacy and Institute of Pharmaceutical Sciences, CHA University, Seongnam, Gyeonggi-do, Republic of Korea
| | - Banu Akdogan
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Judith Nagel
- Institute of Toxicology and Environmental Hygiene, School of Medicine, Technical University Munich, Munich, Germany
| | - Josef Lichtmannegger
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Carola Eberhagen
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Tamara Rieder
- Institute of Toxicology and Environmental Hygiene, School of Medicine, Technical University Munich, Munich, Germany
| | - Mikkel H Vendelbo
- Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark; Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Bernhard Michalke
- Research Unit Analytical BioGeoChemistry, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Ralf Wimmer
- Department of Medicine II, Ludwig Maximilian University Munich, Munich, Germany
| | - Andreas Blutke
- Research Unit Analytical Pathology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Annette Feuchtinger
- Research Unit Analytical Pathology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany
| | - Philip Dershwitz
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa
| | - Ana M DiSpirito
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa
| | - Tawhidul Islam
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - Rui E Castro
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - Byong-Keol Min
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - TaeWon Kim
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - Seoyoung Choi
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - Dasol Kim
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - Chunwon Jung
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - Hongjae Lee
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - Dongsik Park
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - Weonbin Im
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - So-Young Eun
- R&D Center, ArborMed Company Ltd, Pangyo, Seongnam, Gyeonggi-do, Republic of Korea
| | - You-Hee Cho
- Department of Pharmacy, College of Pharmacy and Institute of Pharmaceutical Sciences, CHA University, Seongnam, Gyeonggi-do, Republic of Korea
| | - Jeremy D Semrau
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan
| | - Cecília M P Rodrigues
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - Simon Hohenester
- Department of Medicine II, Ludwig Maximilian University Munich, Munich, Germany
| | | | - Alan A DiSpirito
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa
| | - Hans Zischka
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, Neuherberg, Germany; Institute of Toxicology and Environmental Hygiene, School of Medicine, Technical University Munich, Munich, Germany.
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Xie F, Yuan Q, Qie Y, Meng Y, Luan F. Capacity, stability and energy requirement of divalent mercury uptake by non-methylating/non-demethylating bacteria. JOURNAL OF HAZARDOUS MATERIALS 2023; 450:131074. [PMID: 36848841 DOI: 10.1016/j.jhazmat.2023.131074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/07/2023] [Accepted: 02/21/2023] [Indexed: 06/18/2023]
Abstract
Methylmercury (MeHg) uptake by demethylating bacteria and inorganic divalent mercury [Hg(II)] uptake by methylating bacteria have been extensively investigated because uptake is the initial step of the intracellular Hg transformation. However, MeHg and Hg(II) uptake by non-methylating/non-demethylating bacteria is overlooked, which may play an important role in the biogeochemical cycling of mercury concerning their ubiquitous presence in the environment. Here we report that Shewanella oneidensis MR-1, a model strain of non-methylating/non-demethylating bacteria, can take up and immobilize MeHg and Hg(II) rapidly without intracellular transformation. In addition, when taken up into MR-1 cells, the intracellular MeHg and Hg(II) were proved to be hardly exported over time. In contrast, adsorbed mercury on cell surface was observed to be easily desorbed or remobilized. Moreover, inactivated MR-1 cells (starved and CCCP-treated) were still capable of taking up nonnegligible amounts of MeHg and Hg(II) over an extended period in the absence and presence of cysteine, suggesting that active metabolism may be not required for both MeHg and Hg(II) uptake. Our results provide an improved understanding of divalent mercury uptake by non-methylating/non-demethylating bacteria and highlight the possible broader involvement of these bacteria in mercury cycling in natural environments.
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Affiliation(s)
- Fuyu Xie
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Qingke Yuan
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China
| | - Yukang Qie
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Ying Meng
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China.
| | - Fubo Luan
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
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9
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Stewart A, Dershwitz P, Stewart C, Sawaya MR, Yeates TO, Semrau JD, Zischka H, DiSpirito AA, Bobik TA. Crystal structure of MbnF: an NADPH-dependent flavin monooxygenase from Methylocystis strain SB2. Acta Crystallogr F Struct Biol Commun 2023; 79:111-118. [PMID: 37158309 PMCID: PMC10167746 DOI: 10.1107/s2053230x23003035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 04/02/2023] [Indexed: 05/10/2023] Open
Abstract
Methanobactins (MBs) are ribosomally produced and post-translationally modified peptides (RiPPs) that are used by methanotrophs for copper acquisition. The signature post-translational modification of MBs is the formation of two heterocyclic groups, either an oxazolone, pyrazinedione or imidazolone group, with an associated thioamide from an X-Cys dipeptide. The precursor peptide (MbnA) for MB formation is found in a gene cluster of MB-associated genes. The exact biosynthetic pathway of MB formation is not yet fully understood, and there are still uncharacterized proteins in some MB gene clusters, particularly those that produce pyrazinedione or imidazolone rings. One such protein is MbnF, which is proposed to be a flavin monooxygenase (FMO) based on homology. To help to elucidate its possible function, MbnF from Methylocystis sp. strain SB2 was recombinantly produced in Escherichia coli and its X-ray crystal structure was resolved to 2.6 Å resolution. Based on its structural features, MbnF appears to be a type A FMO, most of which catalyze hydroxylation reactions. Preliminary functional characterization shows that MbnF preferentially oxidizes NADPH over NADH, supporting NAD(P)H-mediated flavin reduction, which is the initial step in the reaction cycle of several type A FMO enzymes. It is also shown that MbnF binds the precursor peptide for MB, with subsequent loss of the leader peptide sequence as well as the last three C-terminal amino acids, suggesting that MbnF might be needed for this process to occur. Finally, molecular-dynamics simulations revealed a channel in MbnF that is capable of accommodating the core MbnA fragment minus the three C-terminal amino acids.
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Affiliation(s)
- Andrew Stewart
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011-3260, USA
| | - Philip Dershwitz
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011-3260, USA
| | - Charles Stewart
- Macromolecular X-ray Crystallography Facility, Office of Biotechnology, Iowa State University, Ames, IA 50011-3260, USA
| | - Michael R Sawaya
- UCLA-DOE Institute for Genomics and Proteomics, University of California Los Angeles, Los Angeles, CA 90095-1570, USA
| | - Todd O Yeates
- UCLA-DOE Institute for Genomics and Proteomics, University of California Los Angeles, Los Angeles, CA 90095-1570, USA
| | - Jeremy D Semrau
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA
| | - Hans Zischka
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Center Munich, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany
| | - Alan A DiSpirito
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011-3260, USA
| | - Thomas A Bobik
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011-3260, USA
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10
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Jiao X, Huang W, Wang A, Wu B, Kang Q, Luo X, Bai L, Deng Z. Crystallographic Deciphering of Spontaneous Self-Assembly of Achiral Calciphores to Chiral Complexes. Chemistry 2023; 29:e202203127. [PMID: 36408990 DOI: 10.1002/chem.202203127] [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: 10/07/2022] [Revised: 11/17/2022] [Accepted: 11/21/2022] [Indexed: 11/23/2022]
Abstract
Thiapyricins (TPC-A/B, 1 and 2), which are new metallophore scaffolds exhibiting selective divalent cation binding property, were produced in response to metal-deprived conditions by Saccharothrix sp. TRM_47004 isolated from the Lop Nor Salt Lake. TPCs represent a thiazolyl-pyridine skeleton of a calcium-binding natural product, calciphore, owing to the selectivity to calcium ions among diverse metal ions. The thiapyricins exhibited notable co-crystalline characteristics of the apo- and holo-forms with racemic enantiomers comprising a pair of space isomers in a Δ/Λ-form. Therefore, we postulated a mechanism for the four-hierarchical self-assembly of achiral natural products into chiral complexes. Furthermore, their metal-chelating trait aided the adaptation of the host during metal starvation by increasing the production of TPCs. This study presents a structural paradigm of a new calciphore, provides insight into the mechanism of natural product assembly, and highlights the causality between the production of the metallophore and metallic habitats.
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Affiliation(s)
- Xingzhi Jiao
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Wei Huang
- College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Anqi Wang
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Banghao Wu
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Qianjin Kang
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Xiaoxia Luo
- College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Linquan Bai
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China.,College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Zixin Deng
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
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11
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Dong H, Huang L, Zhao L, Zeng Q, Liu X, Sheng Y, Shi L, Wu G, Jiang H, Li F, Zhang L, Guo D, Li G, Hou W, Chen H. A critical review of mineral-microbe interaction and coevolution: mechanisms and applications. Natl Sci Rev 2022; 9:nwac128. [PMID: 36196117 PMCID: PMC9522408 DOI: 10.1093/nsr/nwac128] [Citation(s) in RCA: 43] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 06/21/2022] [Accepted: 06/28/2022] [Indexed: 11/12/2022] Open
Abstract
Abstract
The mineral-microbe interactions play important roles in environmental change, biogeochemical cycling of elements, and formation of ore deposits. Minerals provide both beneficial (physical and chemical protection, nutrients, and energy) and detrimental (toxic substances and oxidative pressure) effects to microbes, resulting in mineral-specific microbial colonization. Microbes impact dissolution, transformation, and precipitation of minerals through their activity, resulting in either genetically-controlled or metabolism-induced biomineralization. Through these interactions minerals and microbes coevolve through Earth history. The mineral-microbe interactions typically occur at microscopic scale but the effect is often manifested at global scale. Despite advances achieved through decades of research, major questions remain. Four areas are identified for future research: integrating mineral and microbial ecology, establishing mineral biosignatures, linking laboratory mechanistic investigation to field observation, and manipulating mineral-microbe interactions for the benefit of humankind.
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Affiliation(s)
- Hailiang Dong
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Liuqin Huang
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Wuhan 430074 , China
| | - Linduo Zhao
- Illinois Sustainable Technology Center , Illinois State Water Survey, , Champaign , IL 61820 , USA
- University of Illinois at Urbana-Champaign , Illinois State Water Survey, , Champaign , IL 61820 , USA
| | - Qiang Zeng
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Xiaolei Liu
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Yizhi Sheng
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Liang Shi
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Wuhan 430074 , China
| | - Geng Wu
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Wuhan 430074 , China
| | - Hongchen Jiang
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Wuhan 430074 , China
| | - Fangru Li
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Li Zhang
- Department of Geology and Environmental Earth Science, Miami University , Oxford , OH 45056 , USA
| | - Dongyi Guo
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Gaoyuan Li
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Weiguo Hou
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
| | - Hongyu Chen
- Center for Geomicrobiology and Biogeochemistry Research, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences , Beijing 100083 , China
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12
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Antibiotic resistance and siderophores production by clinical Escherichia coli strains. BIOTECHNOLOGIA 2022; 103:169-184. [PMID: 36606072 PMCID: PMC9642952 DOI: 10.5114/bta.2022.116211] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 02/17/2022] [Accepted: 03/01/2022] [Indexed: 01/09/2023] Open
Abstract
The phenomenon of antibiotic resistance has dramatically increased in the last few decades, especially in enterobacterial pathogens. Different strains of Escherichia coli have been reported to produce a variety of structurally different siderophores. In the present study, 32 E. coli strains were collected from different clinical settings in Cairo, Egypt and subjected to the antibiotic susceptibility test by using 19 antibiotics belonging to 7 classes of chemical groups. The results indicated that 31 strains could be considered as extensively drug-resistant and only one strain as pan drug-resistant. Siderophores production by all the tested E. coli strains was determined qualitatively and quantitatively. Two E. coli strains coded 21 and 49 were found to be the most potent siderophores producers, with 79.9 and 46.62%, respectively. Bacterial colonies with cured plasmids derived from strain 49 showed susceptibility to all the tested antibiotics. Furthermore, E. coli DH5α cells transformed with the plasmid isolated from E. coli strain 21 or E. coli strain 49 were found to be susceptible to ansamycins, quinolones, and sulfonamide groups of antibiotics. In contrast, both plasmid-cured and plasmid-transformed strains did not produce siderophores, indicating that the genes responsible for siderophores production were located on plasmids and regulated by genes located on the chromosome. On the basis of the obtained results, it could be concluded that there is a positive correlation between antibiotic resistance, especially to quinolones and sulfonamide groups, and siderophores production by E. coli strains used in this study.
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13
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Yu RQ, Barkay T. Microbial mercury transformations: Molecules, functions and organisms. ADVANCES IN APPLIED MICROBIOLOGY 2022; 118:31-90. [PMID: 35461663 DOI: 10.1016/bs.aambs.2022.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Mercury (Hg) methylation, methylmercury (MeHg) demethylation, and inorganic redox transformations of Hg are microbe-mediating processes that determine the fate and cycling of Hg and MeHg in many environments, and by doing so influence the health of humans and wild life. The discovery of the Hg methylation genes, hgcAB, in the last decade together with advances in high throughput and genome sequencing methods, have resulted in an expanded appreciation of the diversity of Hg methylating microbes. This review aims to describe experimentally confirmed and recently discovered hgcAB gene-carrying Hg methylating microbes; phylogenetic and taxonomic analyses are presented. In addition, the current knowledge on transformation mechanisms, the organisms that carry them out, and the impact of environmental parameters on Hg methylation, MeHg demethylation, and inorganic Hg reduction and oxidation is summarized. This knowledge provides a foundation for future action toward mitigating the impact of environmental Hg pollution.
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Affiliation(s)
- Ri-Qing Yu
- Department of Biology, University of Texas at Tyler, Tyler, TX, United States.
| | - Tamar Barkay
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States
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14
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Barkay T, Gu B. Demethylation─The Other Side of the Mercury Methylation Coin: A Critical Review. ACS ENVIRONMENTAL AU 2022; 2:77-97. [PMID: 37101582 PMCID: PMC10114901 DOI: 10.1021/acsenvironau.1c00022] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The public and environmental health consequences of mercury (Hg) methylation have drawn much attention and considerable research to Hg methylation processes and their dynamics in diverse environments and under a multitude of conditions. However, the net methylmercury (MeHg) concentration that accumulates in the environment is equally determined by the rate of MeHg degradation, a complex process mediated by a variety of biotic and abiotic mechanisms, about which our knowledge is limited. Here we review the current knowledge on MeHg degradation and its potential pathways and mechanisms. We describe detoxification by resistant microorganisms that employ the Hg resistance (mer) system to reductively break the carbon-mercury (C-Hg) bond producing methane (CH4) and inorganic mercuric Hg(II), which is then reduced by the mercuric reductase to elemental Hg(0). Very recent research has begun to elucidate a mechanism for the long-recognized mer-independent oxidative demethylation, likely involving some strains of anaerobic bacteria as well as aerobic methane-oxidizing bacteria, i.e., methanotrophs. In addition, photochemical and chemical demethylation processes are described, including the roles of dissolved organic matter (DOM) and free radicals as well as dark abiotic demethylation in the natural environment about which little is currently known. We focus on mechanisms and processes of demethylation and highlight the uncertainties and known effects of environmental factors leading to MeHg degradation. Finally, we suggest future research directions to further elucidate the chemical and biochemical mechanisms of biotic and abiotic demethylation and their significance in controlling net MeHg production in natural ecosystems.
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Affiliation(s)
- Tamar Barkay
- Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901, United States
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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15
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Variable Inhibition of Nitrous Oxide Reduction in Denitrifying Bacteria by Different Forms of Methanobactin. Appl Environ Microbiol 2022; 88:e0234621. [PMID: 35285718 DOI: 10.1128/aem.02346-21] [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: 11/20/2022] Open
Abstract
Aerobic methanotrophic activity is highly dependent on copper availability, and methanotrophs have developed multiple strategies to collect copper. Specifically, when copper is limiting (ambient concentrations less than 1 μM), some methanotrophs produce and secret a small modified peptide (less than 1,300 Da) termed methanobactin (MB) that binds copper with high affinity. As MB is secreted into the environment, other microbes that require copper for their metabolism may be inhibited as MB may make copper unavailable; e.g., inhibition of denitrifiers as complete conversion nitrate to dinitrogen involves multiple enzymes, some of which are copper-dependent. Of key concern is inhibition of the copper-dependent nitrous oxide reductase (NosZ), the only known enzyme capable of converting nitrous oxide (N2O) to dinitrogen. Herein, we show that different forms of MB differentially affect copper uptake and N2O reduction by Pseudomonas stutzeri strain DCP-Ps1 (that expresses clade I NosZ) and Dechloromonas aromatica strain RCB (that expresses clade II NosZ). Specifically, in the presence of MB from Methylocystis sp. strain SB2 (SB2-MB), copper uptake and nosZ expression were more significantly reduced than in the presence of MB from Methylosinus trichosporium OB3b (OB3b-MB). Further, N2O accumulation increased more significantly for both P. stutzeri strain DCP-Ps1 and D. aromatica strain RCB in the presence of SB2-MB versus OB3b-MB. These data illustrate that copper competition between methanotrophs and denitrifying bacteria can be significant and that the extent of such competition is dependent on the form of MB that methanotrophs produce. IMPORTANCE Herein, it was demonstrated that the different forms of methanobactin differentially enhance N2O emissions from Pseudomonas stutzeri strain DCP-Ps1 (harboring clade I nitrous oxide reductase) and Dechloromonas aromatica strain RCB (harboring clade II nitrous oxide reductase). This work contributes to our understanding of how aerobic methanotrophs compete with denitrifiers for the copper uptake and also suggests how MBs prevent copper collection by denitrifiers, thus downregulating expression of nitrous oxide reductase. This study provides critical information for enhanced understanding of microbe-microbe interactions that are important for the development of better predictive models of net greenhouse gas emissions (i.e., methane and nitrous oxide) that are significantly controlled by microbial activity.
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16
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To methanotrophy and beyond! New insight into functional and ecological roles for copper chelators. THE ISME JOURNAL 2022; 16:3-4. [PMID: 34593998 PMCID: PMC8692329 DOI: 10.1038/s41396-021-01131-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 01/03/2023]
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17
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Two TonB-dependent transporters in Methylosinus trichosporium OB3b are responsible for uptake of different forms of methanobactin and are involved in the canonical 'copper switch'. Appl Environ Microbiol 2021; 88:e0179321. [PMID: 34669437 DOI: 10.1128/aem.01793-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Copper is an important component of methanotrophic physiology as it controls the expression and activity of alternative forms of methane monooxygenase (MMO). To collect copper, some methanotrophs secrete a chalkophore or copper-binding compound called methanobactin (MB). MB is a ribosomally synthesized post-translationally modified polypeptide (RiPP) that, after binding copper, is collected by MbnT, a TonB-dependent transporter (TBDT). Structurally different forms of MB have been characterized, and here we show that different forms of MB are collected by specific TBDTs. Further, we report that in the model methanotroph, Methylosinus trichosporium OB3b, expression of the TBDT required for uptake of a different MB made by Methylocystis sp. strain SB2 (MB-SB2), is induced in the presence of MB-SB2, suggesting that methanotrophs have developed specific machinery and regulatory systems to actively take up MB from other methanotrophs for copper collection. Moreover, the canonical "copper-switch" in Ms. trichosporium OB3b that controls expression of alternative MMOs is apparent if one of the two TBDTs required for MB-OB3b and MB-SB2 uptake is knocked out, but is disrupted if both TBDTs are knocked out. These data indicate that MB uptake, including the uptake of exogenous MB, plays an important role in the copper switch in M. trichosporium OB3b and thus overall activity. Based on these data, we propose a revised model for the "copper-switch" in this methanotroph that involves MB uptake. IMPORTANCE In this study, we demonstrate that different TonB-dependent transporters (TBDTs) in the model methanotroph Methylosinus trichosporium OB3b are responsible for uptake of either endogenous MB or exogenous MB. Interestingly, the presence of exogenous MB induces expression of its specific TBDT in M. trichosporium OB3b, suggesting that this methanotroph is able to actively take up MB produced by others. This work contributes to our understanding of how microbes collect and compete for copper, and also helps inform how such uptake coordinates the expression of different forms of methane monooxygenase. Such studies are likely to be very important to develop a better understanding of methanotrophic interactions via synthesis and secretion of secondary metabolites such as methanobactin and thus provide additional means whereby these microbes can be manipulated for a variety of environmental and industrial purposes.
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