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Helbich S, Barrantes I, Dos Anjos Borges LG, Pieper DH, Vainshtein Y, Sohn K, Engesser KH. The 2-methylpropene degradation pathway in Mycobacteriaceae family strains. Environ Microbiol 2023; 25:2163-2181. [PMID: 37321960 DOI: 10.1111/1462-2920.16449] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 05/31/2023] [Indexed: 06/17/2023]
Abstract
Mycolicibacterium gadium IBE100 and Mycobacterium paragordonae IBE200 are aerobic, chemoorganoheterotrophic bacteria isolated from activated sludge from a wastewater treatment plant. They use 2-methylpropene (isobutene, 2-MP) as the sole source of carbon and energy. Here, we postulate a degradation pathway of 2-methylpropene derived from whole genome sequencing, differential expression analysis and peptide-mass fingerprinting. Key genes identified are coding for a 4-component soluble diiron monooxygenase with epoxidase activity, an epoxide hydrolase, and a 2-hydroxyisobutyryl-CoA mutase. In both strains, involved genes are arranged in clusters of 61.0 and 58.5 kbp, respectively, which also contain the genes coding for parts of the aerobic pathway of adenosylcobalamin synthesis. This vitamin is essential for the carbon rearrangement reaction catalysed by the mutase. These findings provide data for the identification of potential 2-methylpropene degraders.
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Affiliation(s)
- Steffen Helbich
- Institute for Sanitary Engineering, Water Quality and Solid Waste Management, University of Stuttgart, Stuttgart, Germany
| | - Israel Barrantes
- Microbial Interactions and Processes, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | | - Dietmar H Pieper
- Microbial Interactions and Processes, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Yevhen Vainshtein
- Fraunhofer Institute for Interfacial Engineering and Biotechnology, Stuttgart, Germany
| | - Kai Sohn
- Fraunhofer Institute for Interfacial Engineering and Biotechnology, Stuttgart, Germany
| | - Karl-Heinrich Engesser
- Institute for Sanitary Engineering, Water Quality and Solid Waste Management, University of Stuttgart, Stuttgart, Germany
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Chen Y, Ren H, Kong X, Wu H, Lu Z. A multicomponent propane monooxygenase catalyzes the initial degradation of methyl tert-butyl ether in Mycobacterium vaccae JOB5. Appl Environ Microbiol 2023; 89:e0118723. [PMID: 37823642 PMCID: PMC10617536 DOI: 10.1128/aem.01187-23] [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: 07/10/2023] [Accepted: 08/30/2023] [Indexed: 10/13/2023] Open
Abstract
Methyl tert-butyl ether (MTBE) has been recognized as a groundwater contaminant due to its widespread distribution and potential threat to human health. The limited understanding of the enzymes catalyzing MTBE degradation restricts their application in MTBE bioremediation. In this study, an MTBE-degrading soluble di-iron monooxygenase that clusters phylogenetically with a known propane monooxygenase (PRM) encoded by the prmABCD gene cluster was identified and functionally characterized, revealing their role in MTBE metabolism by Mycobacterium vaccae JOB5. Transcriptome analysis demonstrated that the expression of prmABCD was upregulated when JOB5 was induced by MTBE. Escherichia coli Rosetta heterologously expressing prmABCD from JOB5 could transform MTBE, indicating that the PRM of JOB5 is capable of the initial degradation of MTBE. The loss of the gene encoding the oxygenase α-subunit or β-subunit, the coupling protein, or the reductase disrupted MTBE transformation by the recombinant E. coli Rosetta. In addition, the catalytic capacity of PRM is likely affected by residue G95 in the active site pocket and residues I84, P165, A269, and V270 in the substrate tunnel structure. Mutation of amino acids in the active site and substrate tunnel resulted in inefficiency or inactivation of MTBE degradation, and the activity in 1,4-dioxane (1,4-D) degradation was diminished less than that in MTBE degradation.IMPORTANCEMulticomponent monooxygenases catalyzing the initial hydroxylation of MTBE are important in MTBE biodegradation. Previous studies of MTBE degradation enzymes have focused on P450s, alkane monooxygenase and MTBE monooxygenase, but the vital role of soluble di-iron monooxygenases has rarely been reported. In this study, we deciphered the essential catalytic role of a PRM and revealed the key residues of the PRM in MTBE metabolism. Our findings provide new insight into the MTBE-degrading gene cluster and enzymes in bacteria. This characterization of the PRM associated with MTBE degradation expands our understanding of MTBE-degrading gene diversity and provides a novel candidate enzyme for the bioremediation of MTBE-contaminated sites.
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Affiliation(s)
- Yiyang Chen
- MOE Laboratory of Biosystem Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hao Ren
- MOE Laboratory of Biosystem Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiangyu Kong
- MOE Laboratory of Biosystem Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hao Wu
- MOE Laboratory of Biosystem Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
| | - Zhenmei Lu
- MOE Laboratory of Biosystem Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Cancer Center, Zhejiang University, Hangzhou, Zhejiang, China
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Gunasekaran V, Canela N, Constantí M. Comparative Proteomic Analysis of an Ethyl Tert-Butyl Ether-Degrading Bacterial Consortium. Microorganisms 2022; 10:microorganisms10122331. [PMID: 36557584 PMCID: PMC9781318 DOI: 10.3390/microorganisms10122331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/17/2022] [Accepted: 11/22/2022] [Indexed: 11/29/2022] Open
Abstract
A bacterial consortium capable of degrading ethyl tert-butyl ether (ETBE) as a sole carbon source was enriched and isolated from gasoline-contaminated water. Arthrobacter sp., Herbaspirillum sp., Pseudacidovorax sp., Pseudomonas sp., and Xanthomonas sp. were identified as the initial populations with the 16S rDNA analysis. The consortium aerobically degraded 49% of 50 mg/L of ETBE, in 6 days. The ETBE degrading efficiency of the consortium increased to 98% even with the higher concentrations of ETBE (1000 mg/L) in the subsequent subcultures, which accumulated tert-butyl alcohol (TBA). Xanthomonas sp. and Pseudomonas sp. were identified as the predominant ETBE degrading populations in the final subculture. The metaproteome of the ETBE-grown bacterial consortium was compared with the glucose-grown bacterial consortium, using 2D-DIGE. Proteins related to the ETBE metabolism, stress response, carbon metabolism and chaperones were found to be abundant in the presence of ETBE while proteins related to cell division were less abundant. The metaproteomic study revealed that the ETBE does have an effect on the metabolism of the bacterial consortium. It also enabled us to understand the responses of the complex bacterial consortium to ETBE, thus revealing interesting facts about the ETBE degrading bacterial community.
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Affiliation(s)
- Vijayalakshmi Gunasekaran
- Departament d’Enginyeria Química, Universitat Rovira i Virgili, Av. Països Catalans, 26, 43007 Tarragona, Spain
- FA Bio, Harpenden AL5 2JQ, UK
- Correspondence: (V.G.); (M.C.); Tel.: +34-977-558457 (M.C.)
| | - Núria Canela
- Centre for Omic Sciences (COS), Joint Unit Universitat Rovira i Virgili-EURECAT, Av. Universitat 1, 43204 Reus, Spain
| | - Magda Constantí
- Departament d’Enginyeria Química, Universitat Rovira i Virgili, Av. Països Catalans, 26, 43007 Tarragona, Spain
- Correspondence: (V.G.); (M.C.); Tel.: +34-977-558457 (M.C.)
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4
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Suk WA, Heacock ML, Trottier BA, Amolegbe SM, Avakian MD, Henry HF, Carlin DJ, Reed LG. Assessing the Economic and Societal Benefits of SRP-Funded Research. ENVIRONMENTAL HEALTH PERSPECTIVES 2018; 126:065002. [PMID: 29916809 PMCID: PMC6108577 DOI: 10.1289/ehp3534] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/17/2018] [Accepted: 04/24/2018] [Indexed: 05/30/2023]
Abstract
BACKGROUND The National Institute of Environmental Health Sciences (NIEHS) Superfund Basic Research and Training Program (SRP) funds a wide range of transdisciplinary research projects spanning the biomedical and environmental sciences and engineering, supporting and promoting the application of that research to solving real-world problems. OBJECTIVES We used a case study approach to identify the economic and societal benefits of SRP-funded research, focusing on the use of potentially hazardous substance remediation and site monitoring tools. We also identified successes and challenges involved in translating SRP grantees' research findings and advances into application. DISCUSSION We identified remediation and detection research projects supported by the SRP with the most potential for economic and societal benefits and selected 36 for analysis. To examine the benefits of these applied technologies, we interviewed 28 SRP-supported researchers and 41 partners. Five case studies emerged with the most complete information on cost savings-total savings estimated at >$100 million. Our analysis identified added societal benefits such as creation of small businesses, land and water reuse, sustainable technologies, exposure reduction, and university-industry partnerships. CONCLUSIONS Research funded by the SRP has yielded significant cost savings while providing additional societal benefits. https://doi.org/10.1289/EHP3534.
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Affiliation(s)
- William A Suk
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Michelle L Heacock
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Brittany A Trottier
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | | | | | - Heather F Henry
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
| | - Danielle J Carlin
- Superfund Research Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Research Triangle Park, North Carolina, USA
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Ferrario C, Pittino F, Tagliaferri I, Gandolfi I, Bestetti G, Azzoni RS, Diolaiuti G, Franzetti A, Ambrosini R, Villa S. Bacteria contribute to pesticide degradation in cryoconite holes in an Alpine glacier. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 230:919-926. [PMID: 28738304 DOI: 10.1016/j.envpol.2017.07.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/11/2017] [Accepted: 07/11/2017] [Indexed: 06/07/2023]
Abstract
Organic contaminants deposited on glacier snow and ice are subject to partitioning and degradation processes that determine their environmental fate and, consequently, their accumulation in ice bodies. Among these processes, organic compound degradation by supraglacial bacteria has been investigated to a lesser extent than photo- and chemical degradation. We investigated biodegradation of the organophosphorus insecticide chlorpyrifos (CPF), a xenobiotic tracer that accumulates on glaciers after atmospheric medium- and long-range transport, by installing in situ microcosms on an Alpine glacier to simulate cryoconite hole systems. We found that biodegradation contributed to the removal of CPF from the glacier surface more than photo- and chemical degradation. The high concentration of CPF (2-3 μg g-1 w.w.) detected in cryoconite holes and the estimated half-life of this compound (35-69 days in glacier environment) indicated that biodegradation can significantly reduce CPF concentrations on glaciers and its runoff to downstream ecosystems. The metabolic versatility of cryoconite bacteria suggests that these habitats might contribute to the degradation of a wide class of pollutants. We therefore propose that cryoconite acts as a "biofilter" by accumulating both pollutants and biodegradative microbial communities. The contribution of cryoconite to the removal of organic pollutants should be included in models predicting the environmental fate of these compounds in cold areas.
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Affiliation(s)
- Claudia Ferrario
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
| | - Francesca Pittino
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
| | - Ilario Tagliaferri
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
| | - Isabella Gandolfi
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
| | - Giuseppina Bestetti
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
| | | | | | - Andrea Franzetti
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy.
| | - Roberto Ambrosini
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
| | - Sara Villa
- Dept. of Earth and Environmental Sciences (DISAT), University of Milano-Bicocca, Milano, Italy
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6
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Joshi G, Schmidt R, Scow KM, Denison MS, Hristova KR. Effect of benzene and ethylbenzene on the transcription of methyl-tert-butyl ether degradation genes of Methylibium petroleiphilum PM1. MICROBIOLOGY-SGM 2016; 162:1563-1571. [PMID: 27450417 DOI: 10.1099/mic.0.000338] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Methyl-tert-butyl ether (MTBE) and its degradation by-product, tert-butyl alcohol (TBA), are widespread contaminants detected frequently in groundwater in California. Since MTBE was used as a fuel oxygenate for almost two decades, leaking underground fuel storage tanks are an important source of contamination. Gasoline components such as BTEX (benzene, toluene, ethylbenzene and xylenes) are often present in mixtures with MTBE and TBA. Investigations of interactions between BTEX and MTBE degradation have not yielded consistent trends, and the molecular mechanisms of BTEX compounds' impact on MTBE degradation are not well understood. We investigated trends in transcription of biodegradation genes in the MTBE-degrading bacterium, Methylibium petroleiphilum PM1 upon exposure to MTBE, TBA, ethylbenzene and benzene as individual compounds or in mixtures. We designed real-time quantitative PCR assays to target functional genes of strain PM1 and provide evidence for induction of genes mdpA (MTBE monooxygenase), mdpJ (TBA hydroxylase) and bmoA (benzene monooxygenase) in response to MTBE, TBA and benzene, respectively. Delayed induction of mdpA and mdpJ transcription occurred with mixtures of benzene and MTBE or TBA, respectively. bmoA transcription was similar in the presence of MTBE or TBA with benzene as in their absence. Our results also indicate that ethylbenzene, previously proposed as an inhibitor of MTBE degradation in some bacteria, inhibits transcription of mdpA, mdpJ and bmoAgenes in strain PM1.
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Affiliation(s)
- Geetika Joshi
- Department of Land, Air and Water Resources, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Radomir Schmidt
- Department of Land, Air and Water Resources, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Kate M Scow
- Department of Land, Air and Water Resources, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Michael S Denison
- Department of Environmental Toxicology, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Krassimira R Hristova
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53201, USA.,Department of Land, Air and Water Resources, One Shields Avenue, University of California, Davis, CA 95616, USA
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Good NM, Lamb A, Beck DAC, Martinez-Gomez NC, Kalyuzhnaya MG. C₁-Pathways in Methyloversatilis universalis FAM5: Genome Wide Gene Expression and Mutagenesis Studies. Microorganisms 2015; 3:175-97. [PMID: 27682085 PMCID: PMC5023235 DOI: 10.3390/microorganisms3020175] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/17/2015] [Accepted: 03/26/2015] [Indexed: 11/25/2022] Open
Abstract
Methyloversatilis universalis FAM5 utilizes single carbon compounds such as methanol or methylamine as a sole source of carbon and energy. Expression profiling reveals distinct sets of genes altered during growth on methylamine vs methanol. As expected, all genes for the N-methylglutamate pathway were induced during growth on methylamine. Among other functions responding to the aminated source of C1-carbon, are a heme-containing amine dehydrogenase (Qhp), a distant homologue of formaldehyde activating enzyme (Fae3), molybdenum-containing formate dehydrogenase, ferredoxin reductase, a set of homologues to urea/ammonium transporters and amino-acid permeases. Mutants lacking one of the functional subunits of the amine dehydrogenase (ΔqhpA) or Δfae3 showed no growth defect on C1-compounds. M. universalis FAM5 strains with a lesion in the H4-folate pathway were not able to use any C1-compound, methanol or methylamine. Genes essential for C1-assimilation (the serine cycle and glyoxylate shunt) and H4MTP-pathway for formaldehyde oxidation showed similar levels of expression on both C1-carbon sources. M. universalis FAM5 possesses three homologs of the formaldehyde activating enzyme, a key enzyme of the H4MTP-pathway. Strains lacking the canonical Fae (fae1) lost the ability to grow on both C1-compounds. However, upon incubation on methylamine the fae1-mutant produced revertants (Δfae1R), which regained the ability to grow on methylamine. Double and triple mutants (Δfae1RΔfae3, or Δfae1RΔfae2 or Δfae1RΔfae2Δfae3) constructed in the revertant strain background showed growth similar to the Δfae1R phenotype. The metabolic pathways for utilization of methanol and methylamine in Methyloversatilis universalis FAM5 are reconstructed based on these gene expression and phenotypic data.
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Affiliation(s)
- Nathan M. Good
- Department of Microbiology, University of Washington, Seattle, WA 98195-1700, USA; E-Mails: (N.M.G.); (A.L.)
| | - Andrew Lamb
- Department of Microbiology, University of Washington, Seattle, WA 98195-1700, USA; E-Mails: (N.M.G.); (A.L.)
- Department of Chemical Engineering, University of Washington, Seattle, WA 98195-7735, USA; E-Mails: (D.A.C.B.); (N.C.M.G.)
| | - David A. C. Beck
- Department of Chemical Engineering, University of Washington, Seattle, WA 98195-7735, USA; E-Mails: (D.A.C.B.); (N.C.M.G.)
- eScience Institute, University of Washington, Seattle, WA 98195-1570, USA
| | - N. Cecilia Martinez-Gomez
- Department of Chemical Engineering, University of Washington, Seattle, WA 98195-7735, USA; E-Mails: (D.A.C.B.); (N.C.M.G.)
| | - Marina G. Kalyuzhnaya
- Department of Microbiology, University of Washington, Seattle, WA 98195-1700, USA; E-Mails: (N.M.G.); (A.L.)
- Biology Department, San Diego State University, North Life Science Room 401, San Diego, CA 92182-4614, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-619-594-5626
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Joshi G, Schmidt R, Scow KM, Denison MS, Hristova KR. Gene mdpC plays a regulatory role in the methyl-tert-butyl ether degradation pathway of Methylibium petroleiphilum strain PM1. FEMS Microbiol Lett 2015; 362:fnv029. [PMID: 25724531 DOI: 10.1093/femsle/fnv029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Among the few bacteria known to utilize methyl tert-butyl ether (MTBE) as a sole carbon source, Methylibium petroleiphilum PM1 is a well-characterized organism with a sequenced genome; however, knowledge of the genetic regulation of its MTBE degradation pathway is limited. We investigated the role of a putative transcriptional activator gene, mdpC, in the induction of MTBE-degradation genes mdpA (encoding MTBE monooxygenase) and mdpJ (encoding tert-butyl alcohol hydroxylase) of strain PM1 in a gene-knockout mutant mdpC(-). We also utilized quantitative reverse transcriptase PCR assays targeting genes mdpA, mdpJ and mdpC to determine the effects of the mutation on transcription of these genes. Our results indicate that gene mdpC is involved in the induction of both mdpA and mdpJ in response to MTBE and tert-butyl alcohol (TBA) exposure in PM1. An additional independent mechanism may be involved in the induction of mdpJ in the presence of TBA.
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Affiliation(s)
- Geetika Joshi
- Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA
| | - Radomir Schmidt
- Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA
| | - Kate M Scow
- Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA
| | - Michael S Denison
- Department of Environmental Toxicology, University of California, Davis, CA 95616, USA
| | - Krassimira R Hristova
- Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA Biological Sciences Department, Marquette University, Milwaukee, WI 53201, USA
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9
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Key KC, Sublette KL, Johannes TW, Raes E, Sullivan E, Duba J, Ogles D, Baldwin BR, Biernacki A. An In Situ
Bioreactor for the Treatment of Petroleum Hydrocarbons in Groundwater. ACTA ACUST UNITED AC 2013. [DOI: 10.1002/rem.21357] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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10
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Hicks KA, Schmidt R, Nickelsen MG, Boyle SL, Baker JM, Tornatore PM, Hristova KR, Scow KM. Successful treatment of an MTBE-impacted aquifer using a bioreactor self-colonized by native aquifer bacteria. Biodegradation 2013; 25:41-53. [PMID: 23613160 DOI: 10.1007/s10532-013-9639-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/06/2013] [Indexed: 11/26/2022]
Abstract
A field-scale fixed bed bioreactor was used to successfully treat an MTBE-contaminated aquifer in North Hollywood, CA without requiring inoculation with introduced bacteria. Native bacteria from the MTBE-impacted aquifer rapidly colonized the bioreactor, entering the bioreactor in the contaminated groundwater pumped from the site, and biodegraded MTBE with greater than 99 % removal efficiency. DNA sequencing of the 16S rRNA gene identified MTBE-degrading bacteria Methylibium petroleiphilum in the bioreactor. Quantitative PCR showed M. petroleiphilum enriched by three orders of magnitude in the bioreactor above densities pre-existing in the groundwater. Because treatment was carried out by indigenous rather than introduced organisms, regulatory approval was obtained for implementation of a full-scale bioreactor to continue treatment of the aquifer. In addition, after confirmation of MTBE removal in the bioreactor to below maximum contaminant limit levels (MCL; MTBE = 5 μg L(-1)), treated water was approved for reinjection back into the aquifer rather than requiring discharge to a water treatment system. This is the first treatment system in California to be approved for reinjection of biologically treated effluent into a drinking water aquifer. This study demonstrated the potential for using native microbial communities already present in the aquifer as an inoculum for ex-situ bioreactors, circumventing the need to establish non-native, non-acclimated and potentially costly inoculants. Understanding and harnessing the metabolic potential of native organisms circumvents some of the issues associated with introducing non-native organisms into drinking water aquifers, and can provide a low-cost and efficient remediation technology that can streamline future bioremediation approval processes.
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Affiliation(s)
- Kristin A Hicks
- Department of Land, Air and Water Resources, University of California, One Shields Ave, Davis, CA, 95616, USA
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Ethyl tert-butyl ether (ETBE) biodegradation by a syntrophic association of Rhodococcus sp. IFP 2042 and Bradyrhizobium sp. IFP 2049 isolated from a polluted aquifer. Appl Microbiol Biotechnol 2013; 97:10531-9. [DOI: 10.1007/s00253-013-4803-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 02/20/2013] [Accepted: 02/21/2013] [Indexed: 11/26/2022]
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Constitutive expression of the cytochrome P450 EthABCD monooxygenase system enables degradation of synthetic dialkyl ethers in Aquincola tertiaricarbonis L108. Appl Environ Microbiol 2013; 79:2321-7. [PMID: 23354715 DOI: 10.1128/aem.03348-12] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Rhodococcus ruber IFP 2001, Rhodococcus zopfii IFP 2005, and Gordonia sp. strain IFP 2009, the cytochrome P450 monooxygenase EthABCD catalyzes hydroxylation of methoxy and ethoxy residues in the fuel oxygenates methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). The expression of the IS3-type transposase-flanked eth genes is ETBE dependent and controlled by the regulator EthR (C. Malandain et al., FEMS Microbiol. Ecol. 72:289-296, 2010). In contrast, we demonstrated by reverse transcription-quantitative PCR (RT-qPCR) that the betaproteobacterium Aquincola tertiaricarbonis L108, which possesses the ethABCD genes but lacks ethR, constitutively expresses the P450 system at high levels even when growing on nonether substrates, such as glucose. The mutant strain A. tertiaricarbonis L10, which is unable to degrade dialkyl ethers, resulted from a transposition event mediated by a rolling-circle IS91-type element flanking the eth gene cluster in the wild-type strain L108. The constitutive expression of Eth monooxygenase is likely initiated by the housekeeping sigma factor σ(70), as indicated by the presence in strain L108 of characteristic -10 and -35 binding sites upstream of ethA which are lacking in strain IFP 2001. This enables efficient degradation of diethyl ether, diisopropyl ether, MTBE, ETBE, TAME, and tert-amyl ethyl ether (TAEE) without any lag phase in strain L108. However, ethers with larger residues, n-hexyl methyl ether, tetrahydrofuran, and alkyl aryl ethers, were not attacked by the Eth system at significant rates in resting-cell experiments, indicating that the residue in the ether molecule which is not hydroxylated also contributes to the determination of substrate specificity.
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Ramió-Pujol S, Bañeras L, Artigas J, Romaní AM. Changes of the phenol-degrading bacterial community during the decomposition of submersed Platanus acerifolia leaves. FEMS Microbiol Lett 2012; 338:184-91. [PMID: 23136943 DOI: 10.1111/1574-6968.12046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 10/30/2012] [Accepted: 10/31/2012] [Indexed: 11/27/2022] Open
Abstract
Microorganisms are responsible for the decomposition of plant litter due to their enhanced enzyme capabilities. Among extracellular enzymes, those involved in lignin decomposition are especially relevant in leaf degradation. However, the knowledge of the bacterial contribution to the decomposition of phenol-derived compounds in submerged leaf litter is limited. We have used the large unit of the multicomponent bacterial phenol hydroxylase (LmpH) as a genetic proxy to describe changes in the phenol-degrading bacterial community during the decomposition of Platanus acerifolia leaves in a forested stream. Significant differences were found in the phenol-degrading community when three decomposition stages, initial (day 7), midterm (day 58), and late (day 112), were compared. Estimated Shannon's diversity values decreased significantly from 1.93 (initial) to 0.98 (late). According to the deduced amino acid sequences and the corresponding theoretical kinetic parameters of phenol hydroxylases, the initial community showed a low degree of specialization, presumably resulting from random colonization of leaves. At the late decomposition stage, the bacterial community became more specialized, and LmpH genes similar to high-affinity phenol hydroxylases of Comamonas sp. and Burkholderia cepacia increased. The observed changes in the bacterial community suggested an active role of bacteria during litter decomposition in aquatic environments.
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Affiliation(s)
- Sara Ramió-Pujol
- Institute of Aquatic Ecology, University of Girona, Girona, Spain
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14
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Hyman M. Biodegradation of gasoline ether oxygenates. Curr Opin Biotechnol 2012; 24:443-50. [PMID: 23116604 DOI: 10.1016/j.copbio.2012.10.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 09/17/2012] [Accepted: 10/03/2012] [Indexed: 10/27/2022]
Abstract
Ether oxygenates such as methyl tertiary butyl ether (MTBE) are added to gasoline to improve fuel combustion and decrease exhaust emissions. Ether oxygenates and their tertiary alcohol metabolites are now an important group of groundwater pollutants. This review highlights recent advances in our understanding of the microorganisms, enzymes and pathways involved in both the aerobic and anaerobic biodegradation of these compounds. This review also aims to illustrate how these microbiological and biochemical studies have guided, and have helped refine, molecular and stable isotope-based analytical approaches that are increasingly being used to detect and quantify biodegradation of these compounds in contaminated environments.
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Affiliation(s)
- Michael Hyman
- Department of Microbiology, North Carolina State University, Raleigh, NC 27695, USA.
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15
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Synthesis of short-chain diols and unsaturated alcohols from secondary alcohol substrates by the Rieske nonheme mononuclear iron oxygenase MdpJ. Appl Environ Microbiol 2012; 78:6280-4. [PMID: 22752178 DOI: 10.1128/aem.01434-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rieske nonheme mononuclear iron oxygenase MdpJ of the fuel oxygenate-degrading bacterial strain Aquincola tertiaricarbonis L108 has been described to attack short-chain tertiary alcohols via hydroxylation and desaturation reactions. Here, we demonstrate that also short-chain secondary alcohols can be transformed by MdpJ. Wild-type cells of strain L108 converted 2-propanol and 2-butanol to 1,2-propanediol and 3-buten-2-ol, respectively, whereas an mdpJ knockout mutant did not show such activity. In addition, wild-type cells converted 3-methyl-2-butanol and 3-pentanol to the corresponding desaturation products 3-methyl-3-buten-2-ol and 1-penten-3-ol, respectively. The enzymatic hydroxylation of 2-propanol resulted in an enantiomeric excess of about 70% for the (R)-enantiomer, indicating that this reaction was favored. Likewise, desaturation of (R)-2-butanol to 3-buten-2-ol was about 2.3-fold faster than conversion of the (S)-enantiomer. The biotechnological potential of MdpJ for the synthesis of enantiopure short-chain alcohols and diols as building block chemicals is discussed.
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16
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Yaneva N, Schuster J, Schäfer F, Lede V, Przybylski D, Paproth T, Harms H, Müller RH, Rohwerder T. Bacterial acyl-CoA mutase specifically catalyzes coenzyme B12-dependent isomerization of 2-hydroxyisobutyryl-CoA and (S)-3-hydroxybutyryl-CoA. J Biol Chem 2012; 287:15502-11. [PMID: 22433853 DOI: 10.1074/jbc.m111.314690] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Coenzyme B(12)-dependent acyl-CoA mutases are radical enzymes catalyzing reversible carbon skeleton rearrangements in carboxylic acids. Here, we describe 2-hydroxyisobutyryl-CoA mutase (HCM) found in the bacterium Aquincola tertiaricarbonis as a novel member of the mutase family. HCM specifically catalyzes the interconversion of 2-hydroxyisobutyryl- and (S)-3-hydroxybutyryl-CoA. Like isobutyryl-CoA mutase, HCM consists of a large substrate- and a small B(12)-binding subunit, HcmA and HcmB, respectively. However, it is thus far the only acyl-CoA mutase showing substrate specificity for hydroxylated carboxylic acids. Complete loss of 2-hydroxyisobutyric acid degradation capacity in hcmA and hcmB knock-out mutants established the central role of HCM in A. tertiaricarbonis for degrading substrates bearing a tert-butyl moiety, such as the fuel oxygenate methyl tert-butyl ether (MTBE) and its metabolites. Sequence analysis revealed several HCM-like enzymes in other bacterial strains not related to MTBE degradation, indicating that HCM may also be involved in other pathways. In all strains, hcmA and hcmB are associated with genes encoding for a putative acyl-CoA synthetase and a MeaB-like chaperone. Activity and substrate specificity of wild-type enzyme and active site mutants HcmA I90V, I90F, and I90Y clearly demonstrated that HCM belongs to a new subfamily of B(12)-dependent acyl-CoA mutases.
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Affiliation(s)
- Nadya Yaneva
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research (UFZ), 04318 Leipzig, Germany
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17
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Bacterial degradation of tert-amyl alcohol proceeds via hemiterpene 2-methyl-3-buten-2-ol by employing the tertiary alcohol desaturase function of the Rieske nonheme mononuclear iron oxygenase MdpJ. J Bacteriol 2011; 194:972-81. [PMID: 22194447 DOI: 10.1128/jb.06384-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tertiary alcohols, such as tert-butyl alcohol (TBA) and tert-amyl alcohol (TAA) and higher homologues, are only slowly degraded microbially. The conversion of TBA seems to proceed via hydroxylation to 2-methylpropan-1,2-diol, which is further oxidized to 2-hydroxyisobutyric acid. By analogy, a branched pathway is expected for the degradation of TAA, as this molecule possesses several potential hydroxylation sites. In Aquincola tertiaricarbonis L108 and Methylibium petroleiphilum PM1, a likely candidate catalyst for hydroxylations is the putative tertiary alcohol monooxygenase MdpJ. However, by comparing metabolite accumulations in wild-type strains of L108 and PM1 and in two mdpJ knockout mutants of strain L108, we could clearly show that MdpJ is not hydroxylating TAA to diols but functions as a desaturase, resulting in the formation of the hemiterpene 2-methyl-3-buten-2-ol. The latter is further processed via the hemiterpenes prenol, prenal, and 3-methylcrotonic acid. Likewise, 3-methyl-3-pentanol is degraded via 3-methyl-1-penten-3-ol. Wild-type strain L108 and mdpJ knockout mutants formed isoamylene and isoprene from TAA and 2-methyl-3-buten-2-ol, respectively. It is likely that this dehydratase activity is catalyzed by a not-yet-characterized enzyme postulated for the isomerization of 2-methyl-3-buten-2-ol and prenol. The vitamin requirements of strain L108 growing on TAA and the occurrence of 3-methylcrotonic acid as a metabolite indicate that TAA and hemiterpene degradation are linked with the catabolic route of the amino acid leucine, including an involvement of the biotin-dependent 3-methylcrotonyl coenzyme A (3-methylcrotonyl-CoA) carboxylase LiuBD. Evolutionary aspects of favored desaturase versus hydroxylation pathways for TAA conversion and the possible role of MdpJ in the degradation of higher tertiary alcohols are discussed.
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18
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Formation of alkenes via degradation of tert-alkyl ethers and alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp. Appl Environ Microbiol 2011; 77:5981-7. [PMID: 21742915 DOI: 10.1128/aem.00093-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial degradation pathways of fuel oxygenates such as methyl tert-butyl and tert-amyl methyl ether (MTBE and TAME, respectively) have already been studied in some detail. However, many of the involved enzymes are still unknown, and possible side reactions have not yet been considered. In Aquincola tertiaricarbonis L108, Methylibium petroleiphilum PM1, and Methylibium sp. strain R8, we have now detected volatile hydrocarbons as by-products of the degradation of the tert-alkyl ether metabolites tert-butyl and tert-amyl alcohol (TBA and TAA, respectively). The alkene isobutene was formed only during TBA catabolism, while the beta and gamma isomers of isoamylene were produced only during TAA conversion. Both tert-alkyl alcohol degradation and alkene production were strictly oxygen dependent. However, the relative contribution of the dehydration reaction to total alcohol conversion increased with decreasing oxygen concentrations. In resting-cell experiments where the headspace oxygen content was adjusted to less than 2%, more than 50% of the TAA was converted to isoamylene. Isobutene formation from TBA was about 20-fold lower, reaching up to 4% alcohol turnover at low oxygen concentrations. It is likely that the putative tert-alkyl alcohol monooxygenase MdpJ, belonging to the Rieske nonheme mononuclear iron enzymes and found in all three strains tested, or an associated enzymatic step catalyzed the unusual elimination reaction. This was also supported by the detection of mdpJK genes in MTBE-degrading and isobutene-emitting enrichment cultures obtained from two treatment ponds operating at Leuna, Germany. The possible use of alkene formation as an easy-to-measure indicator of aerobic fuel oxygenate biodegradation in contaminated aquifers is discussed.
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Identification of tertiary butyl alcohol (TBA)-utilizing organisms in BioGAC reactors using 13C-DNA stable isotope probing. Biodegradation 2011; 22:961-72. [DOI: 10.1007/s10532-011-9455-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 01/10/2011] [Indexed: 11/26/2022]
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20
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Toda K, Takahashi R, Iwashina T, Hajika M. Difference in chilling-induced flavonoid profiles, antioxidant activity and chilling tolerance between soybean near-isogenic lines for the pubescence color gene. JOURNAL OF PLANT RESEARCH 2011; 124:173-82. [PMID: 20428921 DOI: 10.1007/s10265-010-0345-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 03/31/2010] [Indexed: 05/29/2023]
Abstract
Chilling tolerance is an important trait of soybeans [Glycine max (L.) Merr.] produced in cool climates. We previously isolated a soybean flavonoid 3' hydroxylase (F3'H) gene corresponding to the T locus, which controls pubescence and seed coat color. A genetic link between the T gene and chilling tolerance has been reported, although the exact underlying mechanisms remain unclear. Using the soybean near-isogenic lines (NILs) To7B (TT) and To7G (tt), we examined the relationship between chilling injury, antioxidant activity and flavonoid profiles associated with chilling treatment (15°C). Chilling injury was more severe in the second trifoliate leaves of To7G than in those of To7B. Hydrogen peroxide accumulation and lipid peroxidation were enhanced by chilling in To7G. Chilling-induced enhancement of antioxidant activity was more prominent in To7B than in To7G. High performance liquid chromatography analysis indicated that the contents of quercetin glycosides and isorhamnetin glycosides (3',4'-dihydroxylated flavonol derivatives) increase in the second trifoliate leaves of To7B after chilling treatment, whereas the same treatment increased kaempferol glycoside (4'-monohydroxylated flavonol derivatives) content in the corresponding leaves of To7G. Histochemical staining also demonstrated chilling-induced flavonoid accumulation. Microarray analysis and real-time reverse transcription-PCR demonstrated that the transcript levels of soybean F3'H are upregulated by chilling. The differences in chilling injury, antioxidant activity and flavonoid species between the two NILs support the notion that soybean F3'H affects chilling tolerance by increasing antioxidant activity via production of 3',4'-dihydroxylated flavonol derivatives.
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Affiliation(s)
- Kyoko Toda
- National Institute of Crop Science, 2-1-18 Kannondai, Tsukuba, Ibaraki 305-8518, Japan.
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21
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Bastida F, Rosell M, Franchini AG, Seifert J, Finsterbusch S, Jehmlich N, Jechalke S, von Bergen M, Richnow HH. Elucidating MTBE degradation in a mixed consortium using a multidisciplinary approach. FEMS Microbiol Ecol 2010; 73:370-84. [PMID: 20491917 DOI: 10.1111/j.1574-6941.2010.00889.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The structure and function of a microbial community capable of biodegrading methyl-tert-butyl ether (MTBE) was characterized using compound-specific stable isotope analysis (CSIA), clone libraries and stable isotope probing of proteins (Protein-SIP). The enrichment culture (US3-M), which originated from a gasoline-impacted site in the United States, has been enriched on MTBE as the sole carbon source. The slope of isotopic enrichment factors (epsilon(C) of -2.29+/-0.03 per thousand; epsilon(H) of -58+/-6 per thousand) for carbon and hydrogen discrimination (Deltadelta(2)H/Deltadelta(13)C) was on average equal to Lambda=24+/-2, a value closely related to the reaction mechanism of MTBE degradation in Methylibium petroleiphilum PM1. 16S rRNA gene libraries revealed sequences belonging to M. petroleiphilum PM1, Hydrogenophaga sp., Thiothrix unzii, Rhodobacter sp., Nocardiodes sp. and different Sphingomonadaceae bacteria. Protein-SIP analysis of the culture grown on (13)C-MTBE as the only carbon source revealed that proteins related to members of the Comamonadaceae family, such as Delftia acidovorans, Acidovorax sp. or Comamonas sp., were not (13)C-enriched, whereas proteins related to M. petroleiphilum PM1 showed an average incorporation of 94.5 atom%(13)C. These results indicate a key role for this species in the degradation of MTBE within the US3-M consortia. The combination of CSIA, molecular biology and Protein-SIP facilitated the analysis of an MTBE-degrading mixed culture from a functional and phylogenetic point of view.
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Affiliation(s)
- Felipe Bastida
- Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany.
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22
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Rohwerder T, Müller RH. Biosynthesis of 2-hydroxyisobutyric acid (2-HIBA) from renewable carbon. Microb Cell Fact 2010; 9:13. [PMID: 20184738 PMCID: PMC2847961 DOI: 10.1186/1475-2859-9-13] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Accepted: 02/25/2010] [Indexed: 11/10/2022] Open
Abstract
Nowadays a growing demand for green chemicals and cleantech solutions is motivating the industry to strive for biobased building blocks. We have identified the tertiary carbon atom-containing 2-hydroxyisobutyric acid (2-HIBA) as an interesting building block for polymer synthesis. Starting from this carboxylic acid, practically all compounds possessing the isobutane structure are accessible by simple chemical conversions, e. g. the commodity methacrylic acid as well as isobutylene glycol and oxide. During recent years, biotechnological routes to 2-HIBA acid have been proposed and significant progress in elucidating the underlying biochemistry has been made. Besides biohydrolysis and biooxidation, now a bioisomerization reaction can be employed, converting the common metabolite 3-hydroxybutyric acid to 2-HIBA by a novel cobalamin-dependent CoA-carbonyl mutase. The latter reaction has recently been discovered in the course of elucidating the degradation pathway of the groundwater pollutant methyl tert-butyl ether (MTBE) in the new bacterial species Aquincola tertiaricarbonis. This discovery opens the ground for developing a completely biotechnological process for producing 2-HIBA. The mutase enzyme has to be active in a suitable biological system producing 3-hydroxybutyryl-CoA, which is the precursor of the well-known bacterial bioplastic polyhydroxybutyrate (PHB). This connection to the PHB metabolism is a great advantage as its underlying biochemistry and physiology is well understood and can easily be adopted towards producing 2-HIBA. This review highlights the potential of these discoveries for a large-scale 2-HIBA biosynthesis from renewable carbon, replacing conventional chemistry as synthesis route and petrochemicals as carbon source.
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Affiliation(s)
- Thore Rohwerder
- Helmholtz Centre for Environmental Research, Department Environmental Microbiology, Leipzig, Germany.
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House AJ, Hyman MR. Effects of gasoline components on MTBE and TBA cometabolism by Mycobacterium austroafricanum JOB5. Biodegradation 2009; 21:525-41. [DOI: 10.1007/s10532-009-9321-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 11/26/2009] [Indexed: 11/28/2022]
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24
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Chistoserdova L, Kalyuzhnaya MG, Lidstrom ME. The expanding world of methylotrophic metabolism. Annu Rev Microbiol 2009; 63:477-99. [PMID: 19514844 DOI: 10.1146/annurev.micro.091208.073600] [Citation(s) in RCA: 261] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the past few years, the field of methylotrophy has undergone a significant transformation in terms of discovery of novel types of methylotrophs, novel modes of methylotrophy, and novel metabolic pathways. This time has also been marked by the resolution of long-standing questions regarding methylotrophy and the challenge of long-standing dogmas. This chapter is not intended to provide a comprehensive review of metabolism of methylotrophic bacteria. Instead we focus on significant recent discoveries that are both refining and transforming the current understanding of methylotrophy as a metabolic phenomenon. We also review new directions in methylotroph ecology that improve our understanding of the role of methylotrophy in global biogeochemical processes, along with an outlook for the future challenges in the field.
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Affiliation(s)
- Ludmila Chistoserdova
- Departments of Chemical Engineering, University of Washington, Seattle, Washington 98195, USA
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25
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Involvement of a novel enzyme, MdpA, in methyl tert-butyl ether degradation in Methylibium petroleiphilum PM1. Appl Environ Microbiol 2008; 74:6631-8. [PMID: 18791002 DOI: 10.1128/aem.01192-08] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methylibium petroleiphilum PM1 is a well-characterized environmental strain capable of complete metabolism of the fuel oxygenate methyl tert-butyl ether (MTBE). Using a molecular genetic system which we established to study MTBE metabolism by PM1, we demonstrated that the enzyme MdpA is involved in MTBE removal, based on insertional inactivation and complementation studies. MdpA is constitutively expressed at low levels but is strongly induced by MTBE. MdpA is also involved in the regulation of tert-butyl alcohol (TBA) removal under certain conditions but is not directly responsible for TBA degradation. Phylogenetic comparison of MdpA to related enzymes indicates close homology to the short-chain hydrolyzing alkane hydroxylases (AH1), a group that appears to be a distinct subfamily of the AHs. The unique, substrate-size-determining residue Thr(59) distinguishes MdpA from the AH1 subfamily as well as from AlkB enzymes linked to MTBE degradation in Mycobacterium austroafricanum.
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26
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Müller RH, Rohwerder T, Harms H. Degradation of fuel oxygenates and their main intermediates by Aquincola tertiaricarbonis L108. MICROBIOLOGY-SGM 2008; 154:1414-1421. [PMID: 18451050 DOI: 10.1099/mic.0.2007/014159-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Growth of Aquincola tertiaricarbonis L108 on the fuel oxygenates methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME), as well as on their main metabolites tert-butyl alcohol (TBA), tert-amyl alcohol (TAA) and 2-hydroxyisobutyrate (2-HIBA) was systematically investigated to characterize the range and rates of oxygenate degradation by this strain. The effective maximum growth rates for MTBE, ETBE and TAME at pH 7 and 30 degrees C were 0.045 h(-1), 0.06 h(-1) and 0.055 h(-1), respectively, whereas TAA, TBA and 2-HIBA permitted growth at rates up to 0.08 h(-1), 0.1 h(-1) and 0.17 h(-1), respectively. The experimental growth yields with all these substrates were high. Yields of 0.55 g dry mass (dm) (g MTBE)(-1), 0.53 g dm (g ETBE)(-1), 0.81 g dm (g TAME)(-1), 0.48 g dm (g TBA)(-1), 0.76 g dm (g TAA)(-1) and 0.54 g dm (g 2-HIBA)(-1) were obtained. Maximum specific degradation rates were 0.92 mmol MTBE h(-1) (g dm)(-1), 1.11 mmol ETBE h(-1) g(-1), 0.66 mmol TAME h(-1) g(-1), 1.19 mmol TAA h(-1) g(-1), 2.82 mmol TBA h(-1) g(-1), and 3.27 mmol 2-HIBA h(-1) g(-1). The relatively high rates with TBA, TAA and 2-HIBA indicate that the transformations of these metabolites did not limit the metabolism of MTBE and the related ether compounds. Despite the fact that these metabolites still carry a tertiary carbon atom that is commonly suspected to confer recalcitrance to the ether oxygenates, the transformation rates were in the same range as those with succinate and fructose. With MTBE, strain L108 grew at pHs between 5.5 and 8.0 at near-maximal rate, whereas no growth was found below pH 5.0 and above pH 9.0. The optimum growth temperature was 30 degrees C, but at 5 degrees C still about 15 % of the maximum rate remained, whereas no growth occurred at 42 degrees C. This indicates that MTBE metabolites are valuable substrates and that A. tertiaricarbonis L108 is a good candidate for bioremediation purposes. The possible origin of its exceptional metabolic capability is discussed in terms of the evolution of enzymic activities involved in the conversion of compounds carrying tertiary butyl groups.
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Affiliation(s)
- Roland H Müller
- UFZ, Helmholtz Centre for Environmental Research, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany
| | - Thore Rohwerder
- Aquatic Biotechnology, Biofilm Centre, University Duisburg-Essen, Geibelstr. 41, D-47057 Duisburg, Germany
| | - Hauke Harms
- UFZ, Helmholtz Centre for Environmental Research, Department of Environmental Microbiology, Permoserstr. 15, D-04318 Leipzig, Germany
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Characterization of a novel methanol dehydrogenase in representatives of Burkholderiales: implications for environmental detection of methylotrophy and evidence for convergent evolution. J Bacteriol 2008; 190:3817-23. [PMID: 18390659 DOI: 10.1128/jb.00180-08] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some members of Burkholderiales are able to grow on methanol but lack the genes (mxaFI) responsible for the well-characterized two-subunit pyrroloquinoline quinone-dependent quinoprotein methanol dehydrogenase that is widespread in methylotrophic Proteobacteria. Here, we characterized novel, mono-subunit enzymes responsible for methanol oxidation in four strains, Methyloversatilis universalis FAM5, Methylibium petroleiphilum PM1, and unclassified Burkholderiales strains RZ18-153 and FAM1. The enzyme from M. universalis FAM5 was partially purified and subjected to matrix-assisted laser desorption ionization-time of fight peptide mass fingerprinting. The resulting peptide spectrum was used to identify a gene candidate in the genome of M. petroleiphilum PM1 (mdh2) predicted to encode a type I alcohol dehydrogenase related to the characterized methanol dehydrogenase large subunits but at less than 35% amino acid identity. Homologs of mdh2 were amplified from M. universalis FAM5 and strains RZ18-153 and FAM1, and mutants lacking mdh2 were generated in three of the organisms. These mutants lost their ability to grow on methanol and ethanol, demonstrating that mdh2 is responsible for oxidation of both substrates. Our findings have implications for environmental detection of methylotrophy and indicate that this ability is widespread beyond populations possessing mxaF, the gene traditionally used as a genetic marker for environmental detection of methanol-oxidizing capability. Our findings also have implications for understanding the evolution of methanol oxidation, suggesting a convergence toward the enzymatic function for methanol oxidation in MxaF and Mdh2-type proteins.
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