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Keppler F, Röhling AN, Jaeger N, Schroll M, Hartmann SC, Greule M. Sources and sinks of chloromethane in a salt marsh ecosystem: constraints from concentration and stable isotope measurements of laboratory incubation experiments. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:627-641. [PMID: 32080692 DOI: 10.1039/c9em00540d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Chloromethane (CH3Cl) is the most abundant long-lived chlorinated organic compound in the atmosphere and contributes significantly to natural stratospheric ozone depletion. Salt marsh ecosystems including halophyte plants are a known source of atmospheric CH3Cl but estimates of their total global source strength are highly uncertain and knowledge of the major production and consumption processes in the atmosphere-halophyte-soil system is yet incomplete. In this study we investigated the halophyte plant, Salicornia europaea, and soil samples from a coastal salt marsh site in Sardinia/Italy for their potential to emit and consume CH3Cl and using flux measurements, stable isotope techniques and Arrhenius plots differentiated between biotic and abiotic processes. Our laboratory approach clearly shows that at least 6 different production and consumption processes are active in controlling atmospheric CH3Cl fluxes of a salt marsh ecosystem. CH3Cl release by dried plant and soil material was substantially higher than that from the fresh material at temperatures ranging from 20 to 70 °C. Results of Arrhenius plots helped to distinguish between biotic and abiotic formation processes in plants and soils. Biotic CH3Cl consumption rates were highest at 30 °C for plants and 50 °C for soils, and microbial uptake was higher in soils with higher organic matter content. Stable isotope techniques helped to distinguish between formation and degradation processes and also provided a deeper insight into potential methyl moiety donor compounds, such as S-adenosyl-l-methionine, S-methylmethionine and pectin, that might be involved in the abiotic and biotic CH3Cl production processes. Our results clearly indicate that cycling of CH3Cl in salt marsh ecosystems is a result of several biotic and abiotic processes occurring simultaneously in the atmosphere-plant-soil system. Important precursor compounds for biotic and abiotic CH3Cl formation might be methionine derivatives and pectin. All formation and degradation processes are temperature dependent and thus environmental changes might affect the strength of each source and sink within salt marsh ecosystems and thus considerably alter total fluxes of CH3Cl from salt marsh ecosystems to the atmosphere.
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Affiliation(s)
- Frank Keppler
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234-236, D-69120 Heidelberg, Germany.
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Keppler F, Barnes JD, Horst A, Bahlmann E, Luo J, Nadalig T, Greule M, Hartmann SC, Vuilleumier S. Chlorine Isotope Fractionation of the Major Chloromethane Degradation Processes in the Environment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:1634-1645. [PMID: 31880153 DOI: 10.1021/acs.est.9b06139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Chloromethane (CH3Cl) is an important source of chlorine in the stratosphere, but detailed knowledge of the magnitude of its sources and sinks is missing. Here, we measured the stable chlorine isotope fractionation (εCl) associated with the major abiotic and biotic CH3Cl sinks in the environment, namely, CH3Cl degradation by hydroxyl (·OH) and chlorine (·Cl) radicals in the troposphere and by reference bacteria Methylorubrum extorquens CM4 and Leisingera methylohalidivorans MB2 from terrestrial and marine environments, respectively. No chlorine isotope fractionation was detected for reaction of CH3Cl with ·OH and ·Cl radicals, whereas a large chlorine isotope fractionation (εCl) of -10.9 ± 0.7‰ (n = 3) and -9.4 ± 0.9 (n = 3) was found for CH3Cl degradation by M. extorquens CM4 and L. methylohalidivorans MB2, respectively. The large difference in chlorine isotope fractionation observed between tropospheric and bacterial degradation of CH3Cl provides an effective isotopic tool to characterize and distinguish between major abiotic and biotic processes contributing to the CH3Cl sink in the environment. Our findings demonstrate the potential of emerging triple-element isotopic approaches including chlorine to carbon and hydrogen analysis for the assessment of global cycling of organochlorines.
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Affiliation(s)
- Frank Keppler
- Institute of Earth Sciences , Heidelberg University , Im Neuenheimer Feld 236 , 69120 Heidelberg , Germany
| | - Jaime D Barnes
- Department of Geological Sciences , University of Texas , Austin , Texas 78712 , United States
| | - Axel Horst
- Department of Isotope Biogeochemistry , Helmholtz Centre for Environmental Research - UFZ , Permoserstr.15 , 04318 Leipzig , Germany
| | - Enno Bahlmann
- Leibniz Institute for Baltic Sea Research Warnemünde , Seestrasse 15 , 18119 Rostock , Germany
| | - Jing Luo
- UMR 7156 CNRS Génétique Moléculaire, Génomique, Microbiologie , Université de Strasbourg , 4 allée Konrad Roentgen , 67000 Strasbourg , France
| | - Thierry Nadalig
- UMR 7156 CNRS Génétique Moléculaire, Génomique, Microbiologie , Université de Strasbourg , 4 allée Konrad Roentgen , 67000 Strasbourg , France
| | - Markus Greule
- Institute of Earth Sciences , Heidelberg University , Im Neuenheimer Feld 236 , 69120 Heidelberg , Germany
| | - S Christoph Hartmann
- Institute of Earth Sciences , Heidelberg University , Im Neuenheimer Feld 236 , 69120 Heidelberg , Germany
- Max Planck Institute for Chemistry , Hahn-Meitner-Weg 1 , 55128 Mainz , Germany
| | - Stéphane Vuilleumier
- UMR 7156 CNRS Génétique Moléculaire, Génomique, Microbiologie , Université de Strasbourg , 4 allée Konrad Roentgen , 67000 Strasbourg , France
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Horst A, Bonifacie M, Bardoux G, Richnow HH. Isotopic Characterization ( 2H, 13C, 37Cl, 81Br) of Abiotic Degradation of Methyl Bromide and Methyl Chloride in Water and Implications for Future Studies. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8813-8822. [PMID: 31286766 DOI: 10.1021/acs.est.9b02165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Methyl bromide (CH3Br) and methyl chloride (CH3Cl) significantly contribute to stratospheric ozone depletion. The atmospheric budgets of both compounds are unbalanced with known degradation processes outweighing known emissions. Stable isotope analysis may be capable to identify and quantify emissions and to achieve a balanced budget. Degradation processes do, however, cause isotope fractionation in methyl halides after emission and hence knowledge about these processes is a crucial prerequisite for any isotopic mass balance approach. In the current study, triple-element isotope analysis (2H, 13C, 37Cl/81Br) was applied to investigate the two main abiotic degradation processes of methyl halides (CH3X) in fresh and seawater: hydrolysis and halide exchange. For CH3Br, nucleophilic attack by both H2O and Cl- caused significant primary carbon and bromine isotope effects accompanied by a secondary inverse hydrogen isotope effect. For CH3Cl only nucleophilic substitution by H2O was observed at significant rates causing large primary carbon and chlorine isotope effects and a secondary inverse hydrogen isotope effect. Observed dual-element isotope ratios differed slightly from literature values for microbial degradation in water and hugely from radical reactions in the troposphere. This bodes well for successfully distinguishing and quantifying degradation processes in atmospheric methyl halides using triple-element isotope analysis.
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Affiliation(s)
- Axel Horst
- Department of Isotope Biogeochemistry , Helmholtz Centre for Environmental Research - UFZ , Permoserstr.15 , 04318 Leipzig , Germany
| | - Magali Bonifacie
- Institut de Physique du Globe de Paris , Sorbonne Paris Cité, Université Paris-Diderot, UMR 7154 CNRS , 1 rue Jussieu , F-75005 Paris , France
| | - Gérard Bardoux
- Institut de Physique du Globe de Paris , Sorbonne Paris Cité, Université Paris-Diderot, UMR 7154 CNRS , 1 rue Jussieu , F-75005 Paris , France
| | - Hans Hermann Richnow
- Department of Isotope Biogeochemistry , Helmholtz Centre for Environmental Research - UFZ , Permoserstr.15 , 04318 Leipzig , Germany
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Jaeger N, Besaury L, Röhling AN, Koch F, Delort AM, Gasc C, Greule M, Kolb S, Nadalig T, Peyret P, Vuilleumier S, Amato P, Bringel F, Keppler F. Chloromethane formation and degradation in the fern phyllosphere. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 634:1278-1287. [PMID: 29660879 DOI: 10.1016/j.scitotenv.2018.03.316] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 03/25/2018] [Accepted: 03/25/2018] [Indexed: 06/08/2023]
Abstract
Chloromethane (CH3Cl) is the most abundant halogenated trace gas in the atmosphere. It plays an important role in natural stratospheric ozone destruction. Current estimates of the global CH3Cl budget are approximate. The strength of the CH3Cl global sink by microbial degradation in soils and plants is under discussion. Some plants, particularly ferns, have been identified as substantial emitters of CH3Cl. Their ability to degrade CH3Cl remains uncertain. In this study, we investigated the potential of leaves from 3 abundant ferns (Osmunda regalis, Cyathea cooperi, Dryopteris filix-mas) to produce and degrade CH3Cl by measuring their production and consumption rates and their stable carbon and hydrogen isotope signatures. Investigated ferns are able to degrade CH3Cl at rates from 2.1 to 17 and 0.3 to 0.9μggdw-1day-1 for C. cooperi and D. filix-mas respectively, depending on CH3Cl supplementation and temperature. The stable carbon isotope enrichment factor of remaining CH3Cl was -39±13‰, whereas negligible isotope fractionation was observed for hydrogen (-8±19‰). In contrast, O. regalis did not consume CH3Cl, but produced it at rates ranging from 0.6 to 128μggdw-1day-1, with stable isotope values of -97±8‰ for carbon and -202±10‰ for hydrogen, respectively. Even though the 3 ferns showed clearly different formation and consumption patterns, their leaf-associated bacterial diversity was not notably different. Moreover, we did not detect genes associated with the only known chloromethane utilization pathway "cmu" in the microbial phyllosphere of the investigated ferns. Our study suggests that still unknown CH3Cl biodegradation processes on plants play an important role in global cycling of atmospheric CH3Cl.
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Affiliation(s)
- Nicole Jaeger
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 236, Heidelberg, Germany.
| | - Ludovic Besaury
- Institut de Chimie de Clermont-Ferrand (ICCF), UMR6096 CNRS-UCA-Sigma, Clermont-Ferrand, France; Université de Strasbourg, CNRS, GMGM UMR 7156, Department of Microbiology, Genomics and the Environment, Strasbourg, France; UMR FARE, Université de Reims Champagne Ardenne, INRA, Reims, France
| | - Amelie Ninja Röhling
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 236, Heidelberg, Germany
| | - Fabien Koch
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 236, Heidelberg, Germany
| | - Anne-Marie Delort
- Institut de Chimie de Clermont-Ferrand (ICCF), UMR6096 CNRS-UCA-Sigma, Clermont-Ferrand, France
| | - Cyrielle Gasc
- Université Clermont Auvergne, INRA, MEDIS, Clermont-Ferrand, France
| | - Markus Greule
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 236, Heidelberg, Germany
| | - Steffen Kolb
- Microbial Biogeochemistry, Research Area Landscape Functioning, Leibniz Centre for Agricultural Landscape Research (ZALF), Müncheberg, Germany
| | - Thierry Nadalig
- Université de Strasbourg, CNRS, GMGM UMR 7156, Department of Microbiology, Genomics and the Environment, Strasbourg, France
| | - Pierre Peyret
- Université Clermont Auvergne, INRA, MEDIS, Clermont-Ferrand, France
| | - Stéphane Vuilleumier
- Université de Strasbourg, CNRS, GMGM UMR 7156, Department of Microbiology, Genomics and the Environment, Strasbourg, France
| | - Pierre Amato
- Institut de Chimie de Clermont-Ferrand (ICCF), UMR6096 CNRS-UCA-Sigma, Clermont-Ferrand, France
| | - Françoise Bringel
- Université de Strasbourg, CNRS, GMGM UMR 7156, Department of Microbiology, Genomics and the Environment, Strasbourg, France
| | - Frank Keppler
- Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 236, Heidelberg, Germany; Heidelberg Center for the Environment HCE, Heidelberg University, Heidelberg, Germany.
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Chen G, Shouakar-Stash O, Phillips E, Justicia-Leon SD, Gilevska T, Sherwood Lollar B, Mack EE, Seger ES, Löffler FE. Dual Carbon-Chlorine Isotope Analysis Indicates Distinct Anaerobic Dichloromethane Degradation Pathways in Two Members of Peptococcaceae. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:8607-8616. [PMID: 29975517 DOI: 10.1021/acs.est.8b01583] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Dichloromethane (DCM) is a probable human carcinogen and frequent groundwater contaminant and contributes to stratospheric ozone layer depletion. DCM is degraded by aerobes harboring glutathione-dependent DCM dehalogenases; however, DCM contamination occurs in oxygen-deprived environments, and much less is known about anaerobic DCM metabolism. Some members of the Peptococcaceae family convert DCM to environmentally benign products including acetate, formate, hydrogen (H2), and inorganic chloride under strictly anoxic conditions. The current study applied stable carbon and chlorine isotope fractionation measurements to the axenic culture Dehalobacterium formicoaceticum and to the consortium RM comprising DCM degrader Candidatus Dichloromethanomonas elyunquensis. Degradation-associated carbon and chlorine isotope enrichment factors (εC and εCl) of -42.4 ± 0.7‰ and -5.3 ± 0.1‰, respectively, were measured in D. formicoaceticum cultures. A similar εCl of -5.2 ± 0.1‰, but a substantially lower εC of -18.3 ± 0.2‰, were determined for Ca. Dichloromethanomonas elyunquensis. The εC and εCl values resulted in distinctly different dual element C-Cl isotope correlations (ΛC/Cl = Δδ13C/Δδ37Cl) of 7.89 ± 0.12 and 3.40 ± 0.03 for D. formicoaceticum and Ca. Dichloromethanomonas elyunquensis, respectively. The distinct ΛC/Cl values obtained for the two cultures imply mechanistically distinct C-Cl bond cleavage reactions, suggesting that members of Peptococcaceae employ different pathways to metabolize DCM. These findings emphasize the utility of dual carbon-chlorine isotope analysis to pinpoint DCM degradation mechanisms and to provide an additional line of evidence that detoxification is occurring at DCM-contaminated sites.
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Affiliation(s)
- Gao Chen
- Center for Environmental Biotechnology, Department of Civil and Environmental Engineering, and Department of Microbiology , University of Tennessee , Knoxville , Tennessee 37996 , United States
| | - Orfan Shouakar-Stash
- Isotope Tracer Technologies Inc. (IT2) , Waterloo , Ontario N2 V 1Z5 , Canada
- Department of Earth and Environmental Sciences , University of Waterloo , Waterloo , Ontario N2L 3G1 , Canada
- School of Engineering , University of Guelph , Guelph , Ontario N1G 2W1 , Canada
| | - Elizabeth Phillips
- Department of Earth Sciences , University of Toronto , Toronto , Ontario M5S 3B1 , Canada
| | - Shandra D Justicia-Leon
- School of Biology , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Tetyana Gilevska
- Department of Earth Sciences , University of Toronto , Toronto , Ontario M5S 3B1 , Canada
| | | | - E Erin Mack
- DuPont Corporate Remediation Group , E. I. DuPont de Nemours and Company , Wilmington , Delaware 19805 , United States
| | - Edward S Seger
- The Chemours Company , Wilmington , Delaware 19899 , United States
| | - Frank E Löffler
- Center for Environmental Biotechnology, Department of Civil and Environmental Engineering, and Department of Microbiology , University of Tennessee , Knoxville , Tennessee 37996 , United States
- Oak Ridge National Laboratory (UT-ORNL) Joint Institute for Biological Sciences (JIBS) and Biosciences Division , University of Tennessee and Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
- Department of Biosystems Engineering and Soil Science , University of Tennessee , Knoxville , Tennessee 37996 , United States
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Jaeger N, Besaury L, Kröber E, Delort AM, Greule M, Lenhart K, Nadalig T, Vuilleumier S, Amato P, Kolb S, Bringel F, Keppler F. Chloromethane Degradation in Soils: A Combined Microbial and Two-Dimensional Stable Isotope Approach. JOURNAL OF ENVIRONMENTAL QUALITY 2018; 47:254-262. [PMID: 29634809 DOI: 10.2134/jeq2017.09.0358] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Chloromethane (CHCl, methyl chloride) is the most abundant volatile halocarbon in the atmosphere and involved in stratospheric ozone depletion. The global CHCl budget, and especially the CHCl sink from microbial degradation in soil, still involves large uncertainties. These may potentially be resolved by a combination of stable isotope analysis and bacterial diversity studies. We determined the stable isotope fractionation of CHCl hydrogen and carbon and investigated bacterial diversity during CHCl degradation in three soils with different properties (forest, grassland, and agricultural soils) and at different temperatures and headspace mixing ratios of CHCl. The extent of chloromethane degradation decreased in the order forest > grassland > agricultural soil. Rates ranged from 0.7 to 2.5 μg g dry wt. d for forest soil, from 0.1 to 0.9 μg g dry wt. d for grassland soil, and from 0.1 to 0.4 μg g dry wt. d for agricultural soil and increased with increasing temperature and CHCl supplementation. The measured mean stable hydrogen enrichment factor of CHCl of -50 ± 13‰ was unaffected by temperature, mixing ratio, or soil type. In contrast, the stable carbon enrichment factor depended on CHCl degradation rates and ranged from -38 to -11‰. Bacterial community composition correlated with soil properties was independent from CHCl degradation or isotope enrichment. Nevertheless, increased abundance after CHCl incubation was observed in 21 bacterial operational taxonomical units (OTUs at the 97% 16S RNA sequence identity level). This suggests that some of these bacterial taxa, although not previously associated with CHCl degradation, may play a role in the microbial CHCl sink in soil.
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Nadalig T, Greule M, Bringel F, Keppler F, Vuilleumier S. Probing the diversity of chloromethane-degrading bacteria by comparative genomics and isotopic fractionation. Front Microbiol 2014; 5:523. [PMID: 25360131 PMCID: PMC4197683 DOI: 10.3389/fmicb.2014.00523] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/19/2014] [Indexed: 11/13/2022] Open
Abstract
Chloromethane (CH3Cl) is produced on earth by a variety of abiotic and biological processes. It is the most important halogenated trace gas in the atmosphere, where it contributes to ozone destruction. Current estimates of the global CH3Cl budget are uncertain and suggest that microorganisms might play a more important role in degrading atmospheric CH3Cl than previously thought. Its degradation by bacteria has been demonstrated in marine, terrestrial, and phyllospheric environments. Improving our knowledge of these degradation processes and their magnitude is thus highly relevant for a better understanding of the global budget of CH3Cl. The cmu pathway, for chloromethane utilisation, is the only microbial pathway for CH3Cl degradation elucidated so far, and was characterized in detail in aerobic methylotrophic Alphaproteobacteria. Here, we reveal the potential of using a two-pronged approach involving a combination of comparative genomics and isotopic fractionation during CH3Cl degradation to newly address the question of the diversity of chloromethane-degrading bacteria in the environment. Analysis of available bacterial genome sequences reveals that several bacteria not yet known to degrade CH3Cl contain part or all of the complement of cmu genes required for CH3Cl degradation. These organisms, unlike bacteria shown to grow with CH3Cl using the cmu pathway, are obligate anaerobes. On the other hand, analysis of the complete genome of the chloromethane-degrading bacterium Leisingera methylohalidivorans MB2 showed that this bacterium does not contain cmu genes. Isotope fractionation experiments with L. methylohalidivorans MB2 suggest that the unknown pathway used by this bacterium for growth with CH3Cl can be differentiated from the cmu pathway. This result opens the prospect that contributions from bacteria with the cmu and Leisingera-type pathways to the atmospheric CH3Cl budget may be teased apart in the future.
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Affiliation(s)
- Thierry Nadalig
- Université de Strasbourg, Equipe Adaptations et Interactions Microbiennes dans l'Environnement, Unitès Mixtes de Recherche 7156 Centre National de la Recherche Scientifique, Génétique Moléculaire, Génomique, Microbiologie Strasbourg, France
| | - Markus Greule
- Institute of Earth Sciences, Ruprecht Karls University Heidelberg Heidelberg, Germany
| | - Françoise Bringel
- Université de Strasbourg, Equipe Adaptations et Interactions Microbiennes dans l'Environnement, Unitès Mixtes de Recherche 7156 Centre National de la Recherche Scientifique, Génétique Moléculaire, Génomique, Microbiologie Strasbourg, France
| | - Frank Keppler
- Institute of Earth Sciences, Ruprecht Karls University Heidelberg Heidelberg, Germany
| | - Stéphane Vuilleumier
- Université de Strasbourg, Equipe Adaptations et Interactions Microbiennes dans l'Environnement, Unitès Mixtes de Recherche 7156 Centre National de la Recherche Scientifique, Génétique Moléculaire, Génomique, Microbiologie Strasbourg, France
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Fluorescence-based bacterial bioreporter for specific detection of methyl halide emissions in the environment. Appl Environ Microbiol 2013; 79:6561-7. [PMID: 23956392 DOI: 10.1128/aem.01738-13] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Methyl halides are volatile one-carbon compounds responsible for substantial depletion of stratospheric ozone. Among them, chloromethane (CH3Cl) is the most abundant halogenated hydrocarbon in the atmosphere. Global budgets of methyl halides in the environment are still poorly understood due to uncertainties in their natural sources, mainly from vegetation, and their sinks, which include chloromethane-degrading bacteria. A bacterial bioreporter for the detection of methyl halides was developed on the basis of detailed knowledge of the physiology and genetics of Methylobacterium extorquens CM4, an aerobic alphaproteobacterium which utilizes chloromethane as the sole source of carbon and energy. A plasmid construct with the promoter region of the chloromethane dehalogenase gene cmuA fused to a promotorless yellow fluorescent protein gene cassette resulted in specific methyl halide-dependent fluorescence when introduced into M. extorquens CM4. The bacterial whole-cell bioreporter allowed detection of methyl halides at femtomolar levels and quantification at concentrations above 10 pM (approximately 240 ppt). As shown for the model chloromethane-producing plant Arabidopsis thaliana in particular, the bioreporter may provide an attractive alternative to analytical chemical methods to screen for natural sources of methyl halide emissions.
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