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Clark K, Taggart DM, Baldwin BR, Ritalahti KM, Murdoch RW, Hatt JK, Löffler FE. Normalized Quantitative PCR Measurements as Predictors for Ethene Formation at Sites Impacted with Chlorinated Ethenes. Environ Sci Technol 2018; 52:13410-13420. [PMID: 30365883 PMCID: PMC6945293 DOI: 10.1021/acs.est.8b04373] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantitative PCR (qPCR) targeting Dehalococcoides mccartyi ( Dhc) biomarker genes supports effective management at sites impacted with chlorinated ethenes. To establish correlations between Dhc biomarker gene abundances and ethene formation (i.e., detoxification), 859 groundwater samples representing 62 sites undergoing monitored natural attenuation or enhanced remediation were analyzed. Dhc 16S rRNA genes and the vinyl chloride (VC) reductive dehalogenase genes bvcA and vcrA were detected in 88% and 61% of samples, respectively, from wells with ethene. Dhc 16S rRNA, bvcA, vcrA, and tceA (implicated in cometabolic reductive VC dechlorination) gene abundances all positively correlated with ethene formation. Significantly greater ethene concentrations were observed when Dhc 16S rRNA gene and VC RDase gene abundances exceeded 107 and 106 copies L-1, respectively, and when Dhc 16S rRNA- and bvcA + vcrA-to-total bacterial 16S rRNA gene ratios exceeded 0.1%. Dhc 16S rRNA gene-to- vcrA/ bvcA ratios near unity also indicated elevated ethene; however, no increased ethene was observed in 19 wells where vcrA and/or bvcA gene copy numbers exceeded Dhc cell numbers 10- to 10 000-fold. Approximately one-third of samples with detectable ethene lacked bvcA, vcrA, and tceA, suggesting that comprehensive understanding of VC detoxification biomarkers has not been achieved. Although the current biomarker suite is incomplete, the data analysis corroborates the value of the available Dhc DNA biomarkers for prognostic and diagnostic groundwater monitoring at sites impacted with chlorinated ethenes.
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Affiliation(s)
- Katherine Clark
- Microbial Insights, Incorporated, 10515 Research Drive, Knoxville, Tennessee 37932, United States
| | - Dora M. Taggart
- Microbial Insights, Incorporated, 10515 Research Drive, Knoxville, Tennessee 37932, United States
| | - Brett R. Baldwin
- Microbial Insights, Incorporated, 10515 Research Drive, Knoxville, Tennessee 37932, United States
| | - Kirsti M. Ritalahti
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Robert W. Murdoch
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Janet K. Hatt
- School of Civil and Environmental Engineering, Atlanta, Georgia 30332-0512
| | - Frank E. Löffler
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Biosystems Engineering & Soil Science, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences Division and Joint Institute for Biological Sciences (JIBS), Oak Ridge National Laboratory, Oak Ridge Tennessee 37831, United States
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Löffler FE, Yan J, Ritalahti KM, Adrian L, Edwards EA, Konstantinidis KT, Müller JA, Fullerton H, Zinder SH, Spormann AM. Dehalococcoides mccartyi gen. nov., sp. nov., obligately organohalide-respiring anaerobic bacteria relevant to halogen cycling and bioremediation, belong to a novel bacterial class, Dehalococcoidia classis nov., order Dehalococcoidales ord. nov. and family Dehalococcoidaceae fam. nov., within the phylum Chloroflexi. Int J Syst Evol Microbiol 2015; 65:2015. [PMID: 26184667 DOI: 10.1099/ijs.0.000308] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Yoon S, Cruz-García C, Sanford R, Ritalahti KM, Löffler FE. Denitrification versus respiratory ammonification: environmental controls of two competing dissimilatory NO3(-)/NO2(-) reduction pathways in Shewanella loihica strain PV-4. ISME J 2015; 9:1093-104. [PMID: 25350157 PMCID: PMC4409154 DOI: 10.1038/ismej.2014.201] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 08/30/2014] [Accepted: 09/05/2014] [Indexed: 11/09/2022]
Abstract
Denitrification and respiratory ammonification are two competing, energy-conserving NO3(-)/NO2(-) reduction pathways that have major biogeochemical consequences for N retention, plant growth and climate. Batch and continuous culture experiments using Shewanella loihica strain PV-4, a bacterium possessing both the denitrification and respiratory ammonification pathways, revealed factors that determine NO3(-)/NO2(-) fate. Denitrification dominated at low carbon-to-nitrogen (C/N) ratios (that is, electron donor-limiting growth conditions), whereas ammonium was the predominant product at high C/N ratios (that is, electron acceptor-limiting growth conditions). pH and temperature also affected NO3(-)/NO2(-) fate, and incubation above pH 7.0 and temperatures of 30 °C favored ammonium formation. Reverse-transcriptase real-time quantitative PCR analyses correlated the phenotypic observations with nirK and nosZ transcript abundances that decreased up to 1600-fold and 27-fold, respectively, under conditions favoring respiratory ammonification. Of the two nrfA genes encoded on the strain PV-4 genome, nrfA0844 transcription decreased only when the chemostat reactor received medium with the lowest C/N ratio of 1.5, whereas nrfA0505 transcription occurred at low levels (≤3.4 × 10(-2) transcripts per cell) under all growth conditions. At intermediate C/N ratios, denitrification and respiratory ammonification occurred concomitantly, and both nrfA0844 (5.5 transcripts per cell) and nirK (0.88 transcripts per cell) were transcribed. Recent findings suggest that organisms with both the denitrification and respiratory ammonification pathways are not uncommon in soil and sediment ecosystems, and strain PV-4 offers a tractable experimental system to explore regulation of dissimilatory NO3(-)/NO2(-) reduction pathways.
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Affiliation(s)
- Sukhwan Yoon
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
- Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Claribel Cruz-García
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Robert Sanford
- Department of Geology, University of Illinois, Urbana, IL, USA
| | - Kirsti M Ritalahti
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
- University of Tennessee and Oak Ridge National Laboratory (UT-ORNL) Joint Institute for Biological Sciences (JIBS) and Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Frank E Löffler
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
- University of Tennessee and Oak Ridge National Laboratory (UT-ORNL) Joint Institute for Biological Sciences (JIBS) and Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA
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Miyazaki M, Sakai S, Ritalahti KM, Saito Y, Yamanaka Y, Saito Y, Tame A, Uematsu K, Löffler FE, Takai K, Imachi H. Sphaerochaeta multiformis sp. nov., an anaerobic, psychrophilic bacterium isolated from subseafloor sediment, and emended description of the genus Sphaerochaeta. Int J Syst Evol Microbiol 2014; 64:4147-4154. [PMID: 25249566 DOI: 10.1099/ijs.0.068148-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An anaerobic, psychrophilic bacterium, strain MO-SPC2(T), was isolated from a methanogenic microbial community in a continuous-flow bioreactor that was established from subseafloor sediments collected from off the Shimokita Peninsula of Japan in the north-western Pacific Ocean. Cells were pleomorphic: spherical, annular, curved rod, helical and coccoid cell morphologies were observed. Motility only occurred in helical cells. Strain MO-SPC2(T) grew at 0-17 °C (optimally at 9 °C), at pH 6.0-8.0 (optimally at pH 6.8-7.2) and in 20-40 g NaCl l(-1) (optimally at 20-30 NaCl l(-1)). The strain grew chemo-organotrophically with mono-, di- and polysaccharides. The major end products of glucose fermentation were acetate, ethanol, hydrogen and carbon dioxide. The abundant polar lipids of strain MO-SPC2(T) were phosphatidylglycolipids, phospholipids and glycolipids. The major cellular fatty acids were C14 : 0, C16 : 0 and C16 : 1ω9. Isoprenoid quinones were not detected. The G+C content of the DNA was 32.3 mol%. 16S rRNA gene-based phylogenetic analysis showed that strain MO-SPC2(T) was affiliated with the genus Sphaerochaeta within the phylum Spirochaetes, and its closest relatives were Sphaerochaeta pleomorpha Grapes(T) (88.4 % sequence identity), Sphaerochaeta globosa Buddy(T) (86.7 %) and Sphaerochaeta coccoides SPN1(T) (85.4 %). Based on phenotypic characteristics and phylogenetic traits, strain MO-SPC2(T) is considered to represent a novel species of the genus Sphaerochaeta, for which the name Sphaerochaeta multiformis sp. nov. is proposed. The type strain is MO-SPC2(T) ( = JCM 17281(T) = DSM 23952(T)). An emended description of the genus Sphaerochaeta is also proposed.
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Affiliation(s)
- Masayuki Miyazaki
- Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Sanae Sakai
- Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Kirsti M Ritalahti
- Joint Institute for Biological Sciences (JIBS) and Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Center for Environmental Biotechnology, Department of Microbiology, Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - Yayoi Saito
- Department of Environmental Systems Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan.,Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Yuko Yamanaka
- Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Yumi Saito
- Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Akihiko Tame
- Section 1 Geochemical Oceanography, Office of Marine Research Department of Marine Science, Marine Works Japan Ltd, Yokosuka, Kanagawa 237-0061, Japan
| | - Katsuyuki Uematsu
- Section 1 Geochemical Oceanography, Office of Marine Research Department of Marine Science, Marine Works Japan Ltd, Yokosuka, Kanagawa 237-0061, Japan
| | - Frank E Löffler
- Joint Institute for Biological Sciences (JIBS) and Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Center for Environmental Biotechnology, Department of Microbiology, Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - Ken Takai
- Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Hiroyuki Imachi
- Department of Subsurface Geobiology Analysis and Research (D-SUGAR), Japan Agency for Marine-Earth Science & Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
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Hatt JK, Ritalahti KM, Ogles DM, Lebrón CA, Löffler FE. Design and application of an internal amplification control to improve Dehalococcoides mccartyi 16S rRNA gene enumeration by qPCR. Environ Sci Technol 2013; 47:11131-8. [PMID: 24053159 DOI: 10.1021/es4019817] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Dehalococcoides mccartyi (Dhc) strains are keystone bacteria for reductive dechlorination of chlorinated ethenes to nontoxic ethene in contaminated aquifers. Enumeration of Dhc biomarker genes using quantitative real-time PCR (qPCR) in groundwater is a key component of site assessment and bioremediation monitoring. Unfortunately, standardized qPCR procedures that recognize impaired measurements due to PCR inhibition, low template DNA concentrations, or analytical error are not available, thus limiting confidence in qPCR data. To improve contemporary approaches for enumerating Dhc in environmental samples, multiplex qPCR assays were designed to quantify the Dhc 16S rRNA gene and one of two different internal amplification controls (IACs): a modified Dhc 16S rRNA gene fragment (Dhc*) and the firefly luciferase gene luc. The Dhc* IAC exhibited competitive inhibition in qPCR with the Dhc 16S rRNA gene template when the ratio of either target was 100-fold greater than the other target. A multiplex qPCR assay with the luc IAC avoided competitive inhibition and accurately quantified Dhc abundances ranging from ∼10 to 10(7) 16S rRNA gene copies per reaction. The addition of ∼10(6) E. coli luc IAC to simulated groundwater amended with the Dhc-containing consortium KB-1 yielded reproducible luc counts after DNA extraction and multiplex qPCR enumeration. The application of the luc IAC assay improved Dhc biomarker gene quantification from simulated groundwater samples and is a valuable approach for "ground truthing" qPCR data obtained in different laboratories, thus reducing ambiguity associated with qPCR enumeration and reproducibility.
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Affiliation(s)
- Janet K Hatt
- School of Civil and Environmental Engineering, Georgia Institute of Technology , 311 Ferst Drive, Atlanta, Georgia 30332, United States
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Yan J, Ritalahti KM, Wagner DD, Löffler FE. Unexpected specificity of interspecies cobamide transfer from Geobacter spp. to organohalide-respiring Dehalococcoides mccartyi strains. Appl Environ Microbiol 2012; 78:6630-6. [PMID: 22773645 PMCID: PMC3426716 DOI: 10.1128/aem.01535-12] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 07/03/2012] [Indexed: 11/20/2022] Open
Abstract
Dehalococcoides mccartyi strains conserve energy from reductive dechlorination reactions catalyzed by corrinoid-dependent reductive dehalogenase enzyme systems. Dehalococcoides lacks the ability for de novo corrinoid synthesis, and pure cultures require the addition of cyanocobalamin (vitamin B(12)) for growth. In contrast, Geobacter lovleyi, which dechlorinates tetrachloroethene to cis-1,2-dichloroethene (cis-DCE), and the nondechlorinating species Geobacter sulfurreducens have complete sets of cobamide biosynthesis genes and produced 12.9 ± 2.4 and 24.2 ± 5.8 ng of extracellular cobamide per liter of culture suspension, respectively, during growth with acetate and fumarate in a completely synthetic medium. G. lovleyi-D. mccartyi strain BAV1 or strain FL2 cocultures provided evidence for interspecies corrinoid transfer, and cis-DCE was dechlorinated to vinyl chloride and ethene concomitant with Dehalococcoides growth. In contrast, negligible increase in Dehalococcoides 16S rRNA gene copies and insignificant dechlorination occurred in G. sulfurreducens-D. mccartyi strain BAV1 or strain FL2 cocultures. Apparently, G. lovleyi produces a cobamide that complements Dehalococcoides' nutritional requirements, whereas G. sulfurreducens does not. Interestingly, Dehalococcoides dechlorination activity and growth could be restored in G. sulfurreducens-Dehalococcoides cocultures by adding 10 μM 5',6'-dimethylbenzimidazole. Observations made with the G. sulfurreducens-Dehalococcoides cocultures suggest that the exchange of the lower ligand generated a cobalamin, which supported Dehalococcoides activity. These findings have implications for in situ bioremediation and suggest that the corrinoid metabolism of Dehalococcoides must be understood to faithfully predict, and possibly enhance, reductive dechlorination activities.
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Affiliation(s)
- Jun Yan
- Department of Microbiology
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Tennessee, USA
| | - Kirsti M. Ritalahti
- Department of Microbiology
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Darlene D. Wagner
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Frank E. Löffler
- Department of Microbiology
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Tennessee, USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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Wagner DD, Hug LA, Hatt JK, Spitzmiller MR, Padilla-Crespo E, Ritalahti KM, Edwards EA, Konstantinidis KT, Löffler FE. Genomic determinants of organohalide-respiration in Geobacter lovleyi, an unusual member of the Geobacteraceae. BMC Genomics 2012; 13:200. [PMID: 22616984 PMCID: PMC3403914 DOI: 10.1186/1471-2164-13-200] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 05/22/2012] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Geobacter lovleyi is a unique member of the Geobacteraceae because strains of this species share the ability to couple tetrachloroethene (PCE) reductive dechlorination to cis-1,2-dichloroethene (cis-DCE) with energy conservation and growth (i.e., organohalide respiration). Strain SZ also reduces U(VI) to U(IV) and contributes to uranium immobilization, making G. lovleyi relevant for bioremediation at sites impacted with chlorinated ethenes and radionuclides. G. lovleyi is the only fully sequenced representative of this distinct Geobacter clade, and comparative genome analyses identified genetic elements associated with organohalide respiration and elucidated genome features that distinguish strain SZ from other members of the Geobacteraceae. RESULTS Sequencing the G. lovleyi strain SZ genome revealed a 3.9 Mbp chromosome with 54.7% GC content (i.e., the percent of the total guanines (Gs) and cytosines (Cs) among the four bases within the genome), and average amino acid identities of 53-56% compared to other sequenced Geobacter spp. Sequencing also revealed the presence of a 77 kbp plasmid, pSZ77 (53.0% GC), with nearly half of its encoded genes corresponding to chromosomal homologs in other Geobacteraceae genomes. Among these chromosome-derived features, pSZ77 encodes 15 out of the 24 genes required for de novo cobalamin biosynthesis, a required cofactor for organohalide respiration. A plasmid with 99% sequence identity to pSZ77 was subsequently detected in the PCE-dechlorinating G. lovleyi strain KB-1 present in the PCE-to-ethene-dechlorinating consortium KB-1. Additional PCE-to-cis-DCE-dechlorinating G. lovleyi strains obtained from the PCE-contaminated Fort Lewis, WA, site did not carry a plasmid indicating that pSZ77 is not a requirement (marker) for PCE respiration within this species. Chromosomal genomic islands found within the G. lovleyi strain SZ genome encode two reductive dehalogenase (RDase) homologs and a putative conjugative pilus system. Despite the loss of many c-type cytochrome and oxidative-stress-responsive genes, strain SZ retained the majority of Geobacter core metabolic capabilities, including U(VI) respiration. CONCLUSIONS Gene acquisitions have expanded strain SZ's respiratory capabilities to include PCE and TCE as electron acceptors. Respiratory processes core to the Geobacter genus, such as metal reduction, were retained despite a substantially reduced number of c-type cytochrome genes. pSZ77 is stably maintained within its host strains SZ and KB-1, likely because the replicon carries essential genes including genes involved in cobalamin biosynthesis and possibly corrinoid transport. Lateral acquisition of the plasmid replicon and the RDase genomic island represent unique genome features of the PCE-respiring G. lovleyi strains SZ and KB-1, and at least the latter signifies adaptation to PCE contamination.
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Affiliation(s)
- Darlene D Wagner
- School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, GA, 30332, USA
| | - Laura A Hug
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 3G5, Canada
| | - Janet K Hatt
- School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA, 30332, USA
| | - Melissa R Spitzmiller
- School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA, 30332, USA
| | - Elizabeth Padilla-Crespo
- Department of Microbiology, University of Tennessee, M409 Walters Life Science Building, 1414 Cumberland Avenue, Knoxville, TN, 37996, USA
| | - Kirsti M Ritalahti
- Department of Microbiology, University of Tennessee, M409 Walters Life Science Building, 1414 Cumberland Avenue, Knoxville, TN, 37996, USA
- Biosciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Bethel Valley Road, Building 1520, Oak Ridge, TN, 37831, USA
| | - Elizabeth A Edwards
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, ON, M5S 3E5, Canada
| | - Konstantinos T Konstantinidis
- School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, GA, 30332, USA
- School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA, 30332, USA
| | - Frank E Löffler
- Department of Microbiology, University of Tennessee, M409 Walters Life Science Building, 1414 Cumberland Avenue, Knoxville, TN, 37996, USA
- Biosciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Bethel Valley Road, Building 1520, Oak Ridge, TN, 37831, USA
- Department of Civil and Environmental Engineering, University of Tennessee, 223 Perkins Hall, Knoxville, TN, 37996, USA
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Löffler FE, Yan J, Ritalahti KM, Adrian L, Edwards EA, Konstantinidis KT, Müller JA, Fullerton H, Zinder SH, Spormann AM. Dehalococcoides mccartyi gen. nov., sp. nov., obligately organohalide-respiring anaerobic bacteria relevant to halogen cycling and bioremediation, belong to a novel bacterial class, Dehalococcoidia classis nov., order Dehalococcoidales ord. nov. and family Dehalococcoidaceae fam. nov., within the phylum Chloroflexi. Int J Syst Evol Microbiol 2012; 63:625-635. [PMID: 22544797 DOI: 10.1099/ijs.0.034926-0] [Citation(s) in RCA: 355] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Six obligately anaerobic bacterial isolates (195(T), CBDB1, BAV1, VS, FL2 and GT) with strictly organohalide-respiring metabolisms were obtained from chlorinated solvent-contaminated aquifers, contaminated and uncontaminated river sediments or anoxic digester sludge. Cells were non-motile with a disc-shaped morphology, 0.3-1 µm in diameter and 0.1-0.2 µm thick, and characteristic indentations on opposite flat sides of the cell. Growth occurred in completely synthetic, reduced medium amended with a haloorganic electron acceptor (mostly chlorinated but also some brominated compounds), hydrogen as electron donor, acetate as carbon source, and vitamins. No other growth-supporting redox couples were identified. Aqueous hydrogen consumption threshold concentrations were <1 nM. Growth ceased when vitamin B(12) was omitted from the medium. Addition of sterile cell-free supernatant of Dehalococcoides-containing enrichment cultures enhanced dechlorination and growth of strains 195 and FL2, suggesting the existence of so-far unidentified stimulants. Dechlorination occurred between pH 6.5 and 8.0 and over a temperature range of 15-35 °C, with an optimum growth temperature between 25 and 30 °C. The major phospholipid fatty acids were 14 : 0 (15.7 mol%), br15 : 0 (6.2 mol%), 16 : 0 (22.7 mol%), 10-methyl 16 : 0 (25.8 mol%) and 18 : 0 (16.6 mol%). Unusual furan fatty acids including 9-(5-pentyl-2-furyl)-nonanoate and 8-(5-hexyl-2-furyl)-octanoate were detected in strains FL2, BAV1 and GT, but not in strains 195(T) and CBDB1. The 16S rRNA gene sequences of the six isolates shared more than 98 % identity, and phylogenetic analysis revealed an affiliation with the phylum Chloroflexi and more than 10 % sequence divergence from other described isolates. The genome sizes and G+C contents ranged from 1.34 to 1.47 Mbp and 47 to 48.9 mol% G+C, respectively. Based on 16S rRNA gene sequence comparisons, genome-wide average nucleotide identity and phenotypic characteristics, the organohalide-respiring isolates represent a new genus and species, for which the name Dehalococcoides mccartyi gen. nov., sp. nov. is proposed. Isolates BAV1 ( = ATCC BAA-2100 = JCM 16839 = KCTC 5957), FL2 ( = ATCC BAA-2098 = DSM 23585 = JCM 16840 = KCTC 5959), GT ( = ATCC BAA-2099 = JCM 16841 = KCTC 5958), CBDB1, 195(T) ( = ATCC BAA-2266(T) = KCTC 15142(T)) and VS are considered strains of Dehalococcoides mccartyi, with strain 195(T) as the type strain. The new class Dehalococcoidia classis nov., order Dehalococcoidales ord. nov. and family Dehalococcoidaceae fam. nov. are described to accommodate the new taxon.
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Affiliation(s)
- Frank E Löffler
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA.,Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| | - Jun Yan
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA.,Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| | - Kirsti M Ritalahti
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| | - Lorenz Adrian
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, D-04318 Leipzig, Germany
| | - Elizabeth A Edwards
- Department of Chemical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Konstantinos T Konstantinidis
- School of Civil and Environmental Engineering and School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Jochen A Müller
- Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, D-04318 Leipzig, Germany
| | - Heather Fullerton
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Stephen H Zinder
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Alfred M Spormann
- Departments of Civil and Environmental Engineering and of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
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Ritalahti KM, Justicia-Leon SD, Cusick KD, Ramos-Hernandez N, Rubin M, Dornbush J, Löffler FE. Sphaerochaeta globosa gen. nov., sp. nov. and Sphaerochaeta pleomorpha sp. nov., free-living, spherical spirochaetes. Int J Syst Evol Microbiol 2011; 62:210-216. [PMID: 21398503 DOI: 10.1099/ijs.0.023986-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Free-living bacteria with spherical cells 0.5-2.5 µm in diameter were isolated from freshwater sediment. 16S rRNA gene sequence analysis placed the new isolates within the phylum Spirochaetes ('spirochaetes'). The isolates never displayed a helical morphology or motility. Growth occurred in the presence of 100 mg ampicillin l(-1) in complex and defined mineral salts medium amended with vitamins, yeast extract and monosaccharides, disaccharides or soluble starch as fermentable substrates. Two distinct isolates, designated Buddy(T) and Grapes(T), exhibited doubling times of 21±2 and 15±1 h in glucose-amended medium and grew at 15-37 and 15-30 °C. Optimum growth was observed between 25 and 30 °C and pH 6.5-7.5, with no growth below pH 5 or above pH 10. Hexose and pentose fermentation yielded ethanol, acetate and formate as major end products. Growth was strictly fermentative and anaerobic, but the isolates tolerated brief oxygen exposure. Nitrate, sulfate, thiosulfate and carbon dioxide were not used as electron acceptors, but soluble Fe(III) was reduced to Fe(II) in glucose-amended medium. The DNA G+C base contents of isolates Buddy(T) and Grapes(T) were 45.5-46.4 and 47.0-49.2 mol%, respectively. Phospholipid fatty acid (PLFA) profiles contained large proportions of C(14:0) and C(16:0) straight-chain saturated fatty acids; C(16:1)ω7c and C(16:1)ω9c dominated the mono-unsaturated PLFAs in isolate Grapes(T), whereas isolate Buddy(T) also possessed C(18:1)ω5c, C(18:1)ω7c and C(18:1)ω9c fatty acids. Branched monoenoic acids accounted for up to 12.4 and 30% of the total PLFA in isolates Grapes(T) and Buddy(T), respectively. Based on their unique morphological features and the phylogenetic distance from their closest relatives, we propose the new genus, Sphaerochaeta gen. nov., to accommodate the new isolates within the novel species Sphaerochaeta globosa sp. nov. (type strain Buddy(T) =DSM 22777(T) =ATCC BAA-1886(T)) and Sphaerochaeta pleomorpha sp. nov. (type strain Grapes(T) =DSM 22778(T) =ATCC BAA-1885(T)). Sphaerochaeta globosa is the type species of the genus.
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Affiliation(s)
- Kirsti M Ritalahti
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| | - Shandra D Justicia-Leon
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.,School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Kathleen D Cusick
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
| | - Natalia Ramos-Hernandez
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.,School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Michael Rubin
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.,School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Jessica Dornbush
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.,School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Frank E Löffler
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA.,Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA
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10
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Ritalahti KM, Hatt JK, Lugmayr V, Henn K, Petrovskis EA, Ogles DM, Davis GA, Yeager CM, Lebrón CA, Löffler FE. Comparing on-site to off-site biomass collection for Dehalococcoides biomarker gene quantification to predict in situ chlorinated ethene detoxification potential. Environ Sci Technol 2010; 44:5127-5133. [PMID: 20545341 DOI: 10.1021/es100408r] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Biostimulation and bioaugmentation have emerged as constructive remedies for chlorinated ethene-contaminated aquifers, and a link between Dehalococcoides (Dhc) bacteria and chlorinated ethene detoxification has been established. To quantify Dhc biomarker genes, groundwater samples are shipped to analytical laboratories where biomass is collected on membrane filters by vacuum filtration for DNA extraction and quantitative real-time PCR analysis. This common practice was compared with a straightforward, on-site filtration approach to Sterivex cartridges. In initial laboratory studies with groundwater amended with known amounts of Dhc target cells, Sterivex cartridges yielded one-third of the total DNA and 9-18% of the Dhc biomarker gene copies compared with vacuum filtration. Upon optimization, DNA yields increased to 94 +/- 38% (+/-SD, n = 10), and quantification of Dhc biomarker genes exceeded the values obtained with the vacuum filtration procedure up to 5-fold. Both methods generated reproducible results when volumes containing >10(4) total Dhc target gene copies were collected. Analysis of on-site and off-site biomass collection procedures corroborated the applicability of the Sterivex cartridge for Dhc biomarker quantification in groundwater. Ethene formation coincided with Dhc cell titers of >2 x 10(6) L(-1) and high (i.e., >10(5)) abundance of the vinyl chloride reductive dehalogenase genes vcrA and/or bvcA; however, high Dhc cell titers alone were insufficient to predict ethene formation. Further, ethene formation occurred at sites with high Dhc cell titers but low or no detectable vcrA or bvcA genes, suggesting that other, not yet identified vinyl chloride reductive dehalogenases contribute to ethene formation. On-site biomass collection with Sterivex cartridges avoids problems associated with shipping groundwater and has broad applicability for biomarker monitoring in aqueous samples.
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Affiliation(s)
- Kirsti M Ritalahti
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996-0845, USA
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11
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Loffler FE, Champine JE, Ritalahti KM, Sprague SJ, Tiedje JM. Complete reductive dechlorination of 1,2-dichloropropane by anaerobic bacteria. Appl Environ Microbiol 2010; 63:2870-5. [PMID: 16535654 PMCID: PMC1389209 DOI: 10.1128/aem.63.7.2870-2875.1997] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transformation of 1,2-dichloropropane (1,2-D) was observed in anaerobic microcosms and enrichment cultures derived from Red Cedar Creek sediment. 1-Chloropropane (1-CP) and 2-CP were detected after an incubation period of 4 weeks. After 4 months the initial amount of 1,2-D was stoichiometrically converted to propene, which was not further transformed. Dechlorination of 1,2-D was not inhibited by 2-bromoethanesulfonate. Sequential 5% (vol/vol) transfers from active microcosms yielded a sediment-free, nonmethanogenic culture, which completely dechlorinated 1,2-D to propene at a rate of 5 nmol min(sup-1) mg of protein(sup-1). No intermediate formation of 1-CP or 2-CP was detected in the sediment-free enrichment culture. A variety of electron donors, including hydrogen, supported reductive dechlorination of 1,2-D. The highest dechlorination rates were observed between 20(deg) and 25(deg)C. In the presence of 1,2-D, the hydrogen threshold concentration was below 1 ppm by volume (ppmv). In addition to 1,2-D, the enrichment culture transformed 1,1-D, 2-bromo-1-CP, tetrachloroethene, 1,1,2,2-tetrachloroethane, and 1,2-dichloroethane to less halogenated compounds. These findings extend our knowledge of the reductive dechlorination process and show that halogenated propanes can be completely dechlorinated by anaerobic bacteria.
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Loffler FE, Ritalahti KM, Tiedje JM. Dechlorination of chloroethenes is inhibited by 2-bromoethanesulfonate in the absence of methanogens. Appl Environ Microbiol 2010; 63:4982-5. [PMID: 16535759 PMCID: PMC1389315 DOI: 10.1128/aem.63.12.4982-4985.1997] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
2-Bromoethanesulfonate (BES) inhibited the reductive dechlorination of chloroethenes in several sediment-free enrichment cultures in the absence of methanogenic archaea. Archaeon-specific PCR primers confirmed the absence of methanogens in the enrichment cultures. BES should not be used to attribute dechlorination activities to methanogens.
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13
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McMurdie PJ, Behrens SF, Müller JA, Göke J, Ritalahti KM, Wagner R, Goltsman E, Lapidus A, Holmes S, Löffler FE, Spormann AM. Localized plasticity in the streamlined genomes of vinyl chloride respiring Dehalococcoides. PLoS Genet 2009; 5:e1000714. [PMID: 19893622 PMCID: PMC2764846 DOI: 10.1371/journal.pgen.1000714] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 10/08/2009] [Indexed: 11/18/2022] Open
Abstract
Vinyl chloride (VC) is a human carcinogen and widespread priority pollutant. Here we report the first, to our knowledge, complete genome sequences of microorganisms able to respire VC, Dehalococcoides sp. strains VS and BAV1. Notably, the respective VC reductase encoding genes, vcrAB and bvcAB, were found embedded in distinct genomic islands (GEIs) with different predicted integration sites, suggesting that these genes were acquired horizontally and independently by distinct mechanisms. A comparative analysis that included two previously sequenced Dehalococcoides genomes revealed a contextually conserved core that is interrupted by two high plasticity regions (HPRs) near the Ori. These HPRs contain the majority of GEIs and strain-specific genes identified in the four Dehalococcoides genomes, an elevated number of repeated elements including insertion sequences (IS), as well as 91 of 96 rdhAB, genes that putatively encode terminal reductases in organohalide respiration. Only three core rdhA orthologous groups were identified, and only one of these groups is supported by synteny. The low number of core rdhAB, contrasted with the high rdhAB numbers per genome (up to 36 in strain VS), as well as their colocalization with GEIs and other signatures for horizontal transfer, suggests that niche adaptation via organohalide respiration is a fundamental ecological strategy in Dehalococccoides. This adaptation has been exacted through multiple mechanisms of recombination that are mainly confined within HPRs of an otherwise remarkably stable, syntenic, streamlined genome among the smallest of any free-living microorganism.
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Affiliation(s)
- Paul J McMurdie
- Departments of Civil and Environmental Engineering and of Chemical Engineering, Stanford University, Stanford, California, United States of America
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14
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Amos BK, Ritalahti KM, Cruz-Garcia C, Padilla-Crespo E, Löffler FE. Oxygen effect on Dehalococcoides viability and biomarker quantification. Environ Sci Technol 2008; 42:5718-5726. [PMID: 18754499 DOI: 10.1021/es703227g] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Oxygen-sensitive Dehalococcoides bacteria play crucial roles in detoxification of chlorinated contaminants (e.g., chlorinated ethenes), and bioremediation monitoring relies on quantification of Dehalococcoides DNA and RNA biomarkers. To explore the effects of oxygen on Dehalococcoides activity, viability, and biomarker quantification, batch experiments with a tetrachloroethene-to-ethene dechlorinating consortium (Bio-Dechlor INOCULUM [BDI]) harboring multiple Dehalococcoides strains were performed to quantify the effects of < or = 4 mg/L dissolved oxygen. Oxygen inhibited reductive dechlorination, and only incomplete dechlorination to vinyl chloride (VC) occurred following oxygen consumption and extended incubation periods (89 days). Following 30 days of oxygen exposure and subsequent oxygen removal (i.e., reversibility experiments), all trichloroethene- (TCE-) fed cultures dechlorinated TCE to VC, but VC dechlorination to ethene occurred in only one out of fourteen replicates. These results suggest that Dehalococcoides strains respond differently to oxygen exposure, and strains catalyzing the VC-to-ethene dechlorination step are more susceptible to oxygen inhibition. Quantitative real-time PCR (qPCR) analysis detected a 1-1.5 order-of-magnitude decrease in the number of Dehalococcoides biomarker genes (i.e., 16S rRNA gene and the reductive dehalogenase [RDase] genes tceA, vcrA, bvcA) in the oxygen-amended cultures, but qPCR analysis failed to distinguish viable, dechlorinating from irreversibly inhibited (nonviable) Dehalococcoides cells. Reverse transcriptase qPCR (RT-qPCR) detected Dehalococcoides gene transcripts in the oxygen-amended, non-dechlorinating cultures, and biomarker transcription did not always correlate with dechlorination (in)activity. Enhanced molecular tools that complement existing protocols and provide quantitative information on the viability and activity of the Dehalococcoides population are desirable.
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Affiliation(s)
- Benjamin K Amos
- School of Civil and Environmental Engineering and School of Biology, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332-0512, USA
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15
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Bedard DL, Ritalahti KM, Löffler FE. The Dehalococcoides population in sediment-free mixed cultures metabolically dechlorinates the commercial polychlorinated biphenyl mixture aroclor 1260. Appl Environ Microbiol 2007; 73:2513-21. [PMID: 17308182 PMCID: PMC1855590 DOI: 10.1128/aem.02909-06] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microbial reductive dechlorination of commercial polychlorinated biphenyl (PCB) mixtures (e.g., Aroclors) in aquatic sediments is crucial to achieve detoxification. Despite extensive efforts over nearly two decades, the microorganisms responsible for Aroclor dechlorination remained elusive. Here we demonstrate that anaerobic bacteria of the Dehalococcoides group derived from sediment of the Housatonic River (Lenox, MA) simultaneously dechlorinate 64 PCB congeners carrying four to nine chlorines in Aroclor 1260 in the sediment-free JN cultures. Quantitative real-time PCR showed that the Dehalococcoides cell titer in JN cultures amended with acetate and hydrogen increased from 7.07 x 10(6) +/- 0.42 x 10(6) to 1.67 x 10(8) +/- 0.04 x 10(8) cells/ml, concomitant with a 64.2% decrease of the PCBs with six or more chlorines in Aroclor 1260. No Dehalococcoides growth occurred in parallel cultures without PCBs. Aroclor 1260 dechlorination supported the growth of 9.25 x 10(8) +/- 0.04 x 10(8) Dehalococcoides cells per mumol of chlorine removed. 16S rRNA gene-targeted PCR analysis of known dechlorinators (i.e., Desulfitobacterium, Dehalobacter, Desulfuromonas, Sulfurospirillum, Anaeromyxobacter, Geobacter, and o-17/DF-1-type Chloroflexi organisms) ruled out any involvement of these bacterial groups in the dechlorination. Our results suggest that the Dehalococcoides population present in the JN cultures also catalyzes in situ dechlorination of Aroclor 1260 in the Housatonic River. The identification of Dehalococcoides organisms as catalysts of extensive Aroclor 1260 dechlorination and our ability to propagate the JN cultures under defined conditions offer opportunities to study the organisms' ecophysiology, elucidate nutritional requirements, identify reductive dehalogenase genes involved in PCB dechlorination, and design molecular tools required for bioremediation applications.
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MESH Headings
- Aroclors/metabolism
- Base Sequence
- Chlorine/metabolism
- Chloroflexi/classification
- Chloroflexi/isolation & purification
- Chloroflexi/metabolism
- Colony Count, Microbial
- DNA, Bacterial/biosynthesis
- DNA, Bacterial/chemistry
- DNA, Bacterial/genetics
- DNA, Ribosomal/chemistry
- DNA, Ribosomal/genetics
- Geologic Sediments/microbiology
- Massachusetts
- Molecular Sequence Data
- Polychlorinated Biphenyls/metabolism
- Polymerase Chain Reaction/methods
- RNA, Ribosomal, 16S/genetics
- Rivers/microbiology
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Water Microbiology
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Affiliation(s)
- Donna L Bedard
- Department of Biology, SC 1W14, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
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Krajmalnik-Brown R, Sung Y, Ritalahti KM, Saunders FM, Löffler FE. Environmental distribution of the trichloroethene reductive dehalogenase gene (tceA) suggests lateral gene transfer among Dehalococcoides. FEMS Microbiol Ecol 2007; 59:206-14. [PMID: 17233752 DOI: 10.1111/j.1574-6941.2006.00243.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The trichloroethene reductive dehalogenase gene (tceA) of Dehalococcoides spp. was detected in 12 of 21 trichloroethene-to-ethene dechlorinating enrichment cultures established from aquifer and sediment samples collected from diverse geographic locations in the USA. Analysis of the tceA chromosomal regions indicated that the tceA genes shared greater than 95% sequence identity, and all shared identical tceAB spacer sequences and tceB genes downstream of tceA. A putative transposable element (PTE) was present 1077 bp downstream of the tceB stop codon in three of eight chromosomal regions analyzed. Sequence identity was interrupted downstream of tceB and upstream or downstream of the PTE, suggesting that intrachromosomal or interchromosomal transfer of tceAB had occurred.
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Affiliation(s)
- Rosa Krajmalnik-Brown
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0512, USA
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Sung Y, Fletcher KE, Ritalahti KM, Apkarian RP, Ramos-Hernández N, Sanford RA, Mesbah NM, Löffler FE. Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium. Appl Environ Microbiol 2006; 72:2775-82. [PMID: 16597982 PMCID: PMC1448980 DOI: 10.1128/aem.72.4.2775-2782.2006] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A bacterial isolate, designated strain SZ, was obtained from noncontaminated creek sediment microcosms based on its ability to derive energy from acetate oxidation coupled to tetrachloroethene (PCE)-to-cis-1,2-dichloroethene (cis-DCE) dechlorination (i.e., chlororespiration). Hydrogen and pyruvate served as alternate electron donors for strain SZ, and the range of electron acceptors included (reduced products are given in brackets) PCE and trichloroethene [cis-DCE], nitrate [ammonium], fumarate [succinate], Fe(III) [Fe(II)], malate [succinate], Mn(IV) [Mn(II)], U(VI) [U(IV)], and elemental sulfur [sulfide]. PCE and soluble Fe(III) (as ferric citrate) were reduced at rates of 56.5 and 164 nmol min(-1) mg of protein(-1), respectively, with acetate as the electron donor. Alternate electron acceptors, such as U(VI) and nitrate, did not inhibit PCE dechlorination and were consumed concomitantly. With PCE, Fe(III) (as ferric citrate), and nitrate as electron acceptors, H(2) was consumed to threshold concentrations of 0.08 +/- 0.03 nM, 0.16 +/- 0.07 nM, and 0.5 +/- 0.06 nM, respectively, and acetate was consumed to 3.0 +/- 2.1 nM, 1.2 +/- 0.5 nM, and 3.6 +/- 0.25 nM, respectively. Apparently, electron acceptor-specific acetate consumption threshold concentrations exist, suggesting that similar to the hydrogen threshold model, the measurement of acetate threshold concentrations offers an additional diagnostic tool to delineate terminal electron-accepting processes in anaerobic subsurface environments. Genetic and phenotypic analyses classify strain SZ as the type strain of the new species, Geobacter lovleyi sp. nov., with Geobacter (formerly Trichlorobacter) thiogenes as the closest relative. Furthermore, the analysis of 16S rRNA gene sequences recovered from PCE-dechlorinating consortia and chloroethene-contaminated subsurface environments suggests that Geobacter lovleyi belongs to a distinct, dechlorinating clade within the metal-reducing Geobacter group. Substrate versatility, consumption of electron donors to low threshold concentrations, and simultaneous reduction of electron acceptors suggest that strain SZ-type organisms have desirable characteristics for bioremediation applications.
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Affiliation(s)
- Youlboong Sung
- Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3228 ES&T Building, Atlanta, GA 30332-0512, USA
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Ritalahti KM, Amos BK, Sung Y, Wu Q, Koenigsberg SS, Löffler FE. Quantitative PCR targeting 16S rRNA and reductive dehalogenase genes simultaneously monitors multiple Dehalococcoides strains. Appl Environ Microbiol 2006; 72:2765-74. [PMID: 16597981 PMCID: PMC1449079 DOI: 10.1128/aem.72.4.2765-2774.2006] [Citation(s) in RCA: 289] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 16S rRNA gene provides insufficient information to infer the range of chloroorganic electron acceptors used by different Dehalococcoides organisms. To overcome this limitation and provide enhanced diagnostic tools for growth measurements, site assessment, and bioremediation monitoring, a quantitative real-time PCR (qPCR) approach targeting 16S rRNA genes and three Dehalococcoides reductive dehalogenase (RDase) genes with assigned function (i.e., tceA, bvcA, and vcrA) was designed and evaluated. qPCR standard curves generated for the RDase genes by use of genomic DNA from Dehalococcoides pure cultures correlated with standard curves obtained for both Bacteria- and Dehalococcoides-targeted 16S rRNA genes, suggesting that the RDase genes are useful targets for quantitative assessment of Dehalococcoides organisms. RDase gene probe/primer pairs were specific for the Dehalococcoides strains known to carry the diagnostic RDase gene sequences, and the qPCR method allowed the detection of as few as 1 to 20 and quantification of as few as 50 to 100 tceA, bvcA, or vcrA gene targets per PCR volume. The qPCR approach was applied to dechlorinating enrichment cultures, microcosms, and samples from a contaminated site. In characterized enrichment cultures where known Dehalococcoides strains were enumerated, the sum of the three RDase genes equaled the total Dehalococcoides cell numbers. In site samples and chloroethane-dechlorinating microcosms, the sum of the three RDase genes was much less than that predicted by Dehalococcoides-targeted qPCR, totaling 10 to 30% of the total Dehalococcoides cell numbers. Hence, a large number of Dehalococcoides spp. contain as-yet-unidentified RDase genes, indicating that our current understanding of the dechlorinating Dehalococcoides community is incomplete.
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Affiliation(s)
- Kirsti M Ritalahti
- Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3230 ES&T Building, Atlanta, GA 30332-0512, USA.
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Sung Y, Ritalahti KM, Apkarian RP, Löffler FE. Quantitative PCR confirms purity of strain GT, a novel trichloroethene-to-ethene-respiring Dehalococcoides isolate. Appl Environ Microbiol 2006; 72:1980-7. [PMID: 16517646 PMCID: PMC1393247 DOI: 10.1128/aem.72.3.1980-1987.2006] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A novel Dehalococcoides isolate capable of metabolic trichloroethene (TCE)-to-ethene reductive dechlorination was obtained from contaminated aquifer material. Growth studies and 16S rRNA gene-targeted analyses suggested culture purity; however, the careful quantitative analysis of Dehalococcoides 16S rRNA gene and chloroethene reductive dehalogenase gene (i.e., vcrA, tceA, and bvcA) copy numbers revealed that the culture consisted of multiple, distinct Dehalococcoides organisms. Subsequent transfers, along with quantitative PCR monitoring, yielded isolate GT, possessing only vcrA. These findings suggest that commonly used qualitative 16S rRNA gene-based procedures are insufficient to verify purity of Dehalococcoides cultures. Phylogenetic analysis revealed that strain GT is affiliated with the Pinellas group of the Dehalococcoides cluster and shares 100% 16S rRNA gene sequence identity with two other Dehalococcoides isolates, strain FL2 and strain CBDB1. The new isolate is distinct, as it respires the priority pollutants TCE, cis-1,2-dichloroethene (cis-DCE), 1,1-dichloroethene (1,1-DCE), and vinyl chloride (VC), thereby producing innocuous ethene and inorganic chloride. Strain GT dechlorinated TCE, cis-DCE, 1,1-DCE, and VC to ethene at rates up to 40, 41, 62, and 127 micromol liter-1 day-1, respectively, but failed to dechlorinate PCE. Hydrogen was the required electron donor, which was depleted to a consumption threshold concentration of 0.76+/-0.13 nM with VC as the electron acceptor. In contrast to the known TCE dechlorinating isolates, strain GT dechlorinated TCE to ethene with very little formation of chlorinated intermediates, suggesting that this type of organism avoids the commonly observed accumulation of cis-DCE and VC during TCE-to-ethene dechlorination.
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Affiliation(s)
- Youlboong Sung
- Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3228 ES&T Building, Atlanta, GA 30332-0512, USA
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He J, Sung Y, Krajmalnik-Brown R, Ritalahti KM, Löffler FE. Isolation and characterization of Dehalococcoides sp. strain FL2, a trichloroethene (TCE)- and 1,2-dichloroethene-respiring anaerobe. Environ Microbiol 2005; 7:1442-50. [PMID: 16104866 DOI: 10.1111/j.1462-2920.2005.00830.x] [Citation(s) in RCA: 185] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A strictly anaerobic bacterium was isolated from tetrachloroethene (PCE)-to-ethene dechlorinating microcosms established with river sediment without prior exposure to chlorinated solvents. The isolation procedure included the addition of 2-bromoethanesulfonate to select against methanogenic archaea, >50 consecutive 1-2% (v/v) transfers to reduced mineral salts medium amended with trichloroethene (TCE), acetate, and hydrogen, the addition of ampicillin, and the dilution-to-extinction principle. Culture-dependent and 16S rRNA gene-targeted approaches suggested culture purity. Microscopic examination revealed a homogeneous culture of an organism with a distinct, disc-shaped morphology. The isolate shared >99% 16S rRNA gene sequence similarity with members of the Pinellas group of the Dehalococcoides cluster, and was designated Dehalococcoides sp. strain FL2. Strain FL2 could be propagated with TCE, cis-1,2-dichloroethene (cis-DCE), or trans-DCE as the electron acceptors, acetate as the carbon source, and hydrogen as the electron donor in defined, completely synthetic medium. No other growth-supporting redox couples were identified. Trichloroethene, cis-DCE and trans-DCE were dechlorinated at rates of 27.5, 30.4 and 18.8 micromol l-1 day-1 respectively. Quantitative real-time polymerase chain reaction (PCR) with a fluorescently labelled linear hybridization probe confirmed growth with these electron acceptors, and suggested that strain FL2 captures energy from both the TCE-to-cis-DCE and 1,2-DCE-to-VC dechlorination steps. Tetrachloroethene and vinyl chloride (VC) were slowly and cometabolically dechlorinated in the presence of a growth-supporting chloroethene, but ethene formation was incomplete, even after prolonged incubation. At room temperature, strain FL2 grew with a doubling time of 2.4 days, and yielded 166.1+/-10.2 mg of protein per mole of chloride released. In the presence of excess electron acceptor, strain FL2 consumed hydrogen to a concentration of 0.061+/-0.016 nM. Dechlorination ceased following the addition of 0.5 mM sulfite, whereas sulfate (10 mM) and nitrate (5 mM) had no inhibitory effects.
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Affiliation(s)
- Jianzhong He
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
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Ritalahti KM, Löffler FE, Rasch EE, Koenigsberg SS. Bioaugmentation for chlorinated ethene detoxification: Bioaugmentation and molecular diagnostics in the bioremediation of chlorinated ethene-contaminated sites. Ind Biotechnol (New Rochelle N Y) 2005. [DOI: 10.1089/ind.2005.1.114] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Kirsti M. Ritalahti
- Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3228 ES&T Building, Atlanta, Georgia 30332-0512
| | - Frank E. Löffler
- Georgia Institute of Technology, School of Civil and Environmental Engineering, 311 Ferst Drive, 3228 ES&T Building, Atlanta, Georgia 30332-0512
| | - Erin E. Rasch
- Regenesis, 1011 Calle Sombra, San Clemente, CA 92673
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Abstract
Strategies and procedures for enriching, isolating, and cultivating reductively dechlorinating bacteria that use chloroorganic compounds as metabolic electron acceptors from environmental samples are described. Further, nucleic acid-based approaches used to detect and quantify dechlorinator (i.e., Dehalococcoides)-specific genes are presented.
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Affiliation(s)
- Frank E Löffler
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332-0512, USA
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Krajmalnik-Brown R, Hölscher T, Thomson IN, Saunders FM, Ritalahti KM, Löffler FE. Genetic identification of a putative vinyl chloride reductase in Dehalococcoides sp. strain BAV1. Appl Environ Microbiol 2004; 70:6347-51. [PMID: 15466590 PMCID: PMC522117 DOI: 10.1128/aem.70.10.6347-6351.2004] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dehalococcoides sp. strain BAV1 couples growth with the reductive dechlorination of vinyl chloride (VC) to ethene. Degenerate primers targeting conserved regions in reductive dehalogenase (RDase) genes were designed and used to PCR amplify putative RDase genes from strain BAV1. Seven unique RDase gene fragments were identified. Transcription analysis of VC-grown BAV1 cultures suggested that bvcA was involved in VC reductive dechlorination, and the complete sequence of bvcA was obtained. bvcA was absent in Dehalococcoides isolates that failed to respire VC, yet was detected in four of eight VC-respiring mixed cultures.
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Affiliation(s)
- Rosa Krajmalnik-Brown
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0512, USA.
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Hölscher T, Krajmalnik-Brown R, Ritalahti KM, Von Wintzingerode F, Görisch H, Löffler FE, Adrian L. Multiple nonidentical reductive-dehalogenase-homologous genes are common in Dehalococcoides. Appl Environ Microbiol 2004; 70:5290-7. [PMID: 15345412 PMCID: PMC520921 DOI: 10.1128/aem.70.9.5290-5297.2004] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Degenerate primers were used to amplify large fragments of reductive-dehalogenase-homologous (RDH) genes from genomic DNA of two Dehalococcoides populations, the chlorobenzene- and dioxin-dechlorinating strain CBDB1 and the trichloroethene-dechlorinating strain FL2. The amplicons (1,350 to 1,495 bp) corresponded to nearly complete open reading frames of known reductive dehalogenase genes and short fragments (approximately 90 bp) of genes encoding putative membrane-anchoring proteins. Cloning and restriction analysis revealed the presence of at least 14 different RDH genes in each strain. All amplified RDH genes showed sequence similarity with known reductive dehalogenase genes over the whole length of the sequence and shared all characteristics described for reductive dehalogenases. Deduced amino acid sequences of seven RDH genes from strain CBDB1 were 98.5 to 100% identical to seven different RDH genes from strain FL2, suggesting that both strains have an overlapping substrate range. All RDH genes identified in strains CBDB1 and FL2 were related to the RDH genes present in the genomes of Dehalococcoides ethenogenes strain 195 and Dehalococcoides sp. strain BAV1; however, sequence identity did not exceed 94.4 and 93.1%, respectively. The presence of RDH genes in strains CBDB1, FL2, and BAV1 that have no orthologs in strain 195 suggests that these strains possess dechlorination activities not present in strain 195. Comparative sequence analysis identified consensus sequences for cobalamin binding in deduced amino acid sequences of seven RDH genes. In conclusion, this study demonstrates that the presence of multiple nonidentical RDH genes is characteristic of Dehalococcoides strains.
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Affiliation(s)
- Tina Hölscher
- School of Civil and Environmental Engineering, 311 Ferst Dr., 3228 ES and T Building, Georgia Institute of Technology, Atlanta, GA 30332-0512, USA
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Ritalahti KM, Löffler FE. Populations implicated in anaerobic reductive dechlorination of 1,2-dichloropropane in highly enriched bacterial communities. Appl Environ Microbiol 2004; 70:4088-95. [PMID: 15240287 PMCID: PMC444787 DOI: 10.1128/aem.70.7.4088-4095.2004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
1,2-Dichloropropane (1,2-D), a widespread groundwater contaminant, can be reductively dechlorinated to propene by anaerobic bacteria. To shed light on the populations involved in the detoxification process, a comprehensive 16S rRNA gene-based bacterial community analysis of two enrichment cultures derived from geographically distinct locations was performed. Analysis of terminal restriction fragments, amplicons obtained with dechlorinator-specific PCR primers, and enumeration with quantitative real-time PCR as well as screening clone libraries all implied that Dehalococcoides populations were involved in 1,2-D dechlorination in both enrichment cultures. Physiological traits (e.g., dechlorination in the presence of ampicillin and a requirement for hydrogen as the electron donor) supported the involvement of Dehalococcoides populations in the dechlorination process. These findings expand the spectrum of chloroorganic compounds used by Dehalococcoides species as growth-supporting electron acceptors. The combined molecular approach allowed a comparison between different 16S rRNA gene-based approaches for the detection of Dehalococcoides populations.
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Affiliation(s)
- Kirsti M Ritalahti
- School of Civil and Environmental Engineering, 311 Ferst Dr., 3228 ES&T Building, Georgia Institute of Technology, Atlanta, GA 30332-0512, USA
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He J, Ritalahti KM, Yang KL, Koenigsberg SS, Löffler FE. Detoxification of vinyl chloride to ethene coupled to growth of an anaerobic bacterium. Nature 2003; 424:62-5. [PMID: 12840758 DOI: 10.1038/nature01717] [Citation(s) in RCA: 313] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2003] [Accepted: 04/29/2003] [Indexed: 11/09/2022]
Abstract
Tetrachloroethene (PCE) and trichloroethene (TCE) are ideal solvents for numerous applications, and their widespread use makes them prominent groundwater pollutants. Even more troubling, natural biotic and abiotic processes acting on these solvents lead to the accumulation of toxic intermediates (such as dichloroethenes) and carcinogenic intermediates (such as vinyl chloride). Vinyl chloride was found in at least 496 of the 1,430 National Priorities List sites identified by the US Environmental Protection Agency, and its precursors PCE and TCE are present in at least 771 and 852 of these sites, respectively. Here we describe an unusual, strictly anaerobic bacterium that destroys dichloroethenes and vinyl chloride as part of its energy metabolism, generating environmentally benign products (biomass, ethene and inorganic chloride). This organism might be useful for cleaning contaminated subsurface environments and restoring drinking-water reservoirs.
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Affiliation(s)
- Jianzhong He
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0512, USA
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Sung Y, Ritalahti KM, Sanford RA, Urbance JW, Flynn SJ, Tiedje JM, Löffler FE. Characterization of two tetrachloroethene-reducing, acetate-oxidizing anaerobic bacteria and their description as Desulfuromonas michiganensis sp. nov. Appl Environ Microbiol 2003; 69:2964-74. [PMID: 12732573 PMCID: PMC154526 DOI: 10.1128/aem.69.5.2964-2974.2003] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2002] [Accepted: 01/30/2003] [Indexed: 11/20/2022] Open
Abstract
Two tetrachlorethene (PCE)-dechlorinating populations, designated strains BB1 and BRS1, were isolated from pristine river sediment and chloroethene-contaminated aquifer material, respectively. PCE-to-cis-1,2-dichloroethene-dechlorinating activity could be transferred in defined basal salts medium with acetate as the electron donor and PCE as the electron acceptor. Taxonomic analysis based on 16S rRNA gene sequencing placed both isolates within the Desulfuromonas cluster in the delta subdivision of the Proteobacteria. PCE was dechlorinated at rates of at least 139 nmol min(-1) mg of protein(-1) at pH values between 7.0 and 7.5 and temperatures between 25 and 30 degrees C. Dechlorination also occurred at 10 degrees C. The electron donors that supported dechlorination included acetate, lactate, pyruvate, succinate, malate, and fumarate but not hydrogen, formate, ethanol, propionate, or sulfide. Growth occurred with malate or fumarate alone, whereas oxidation of the other electron donors depended strictly on the presence of fumarate, malate, ferric iron, sulfur, PCE, or TCE as an electron acceptor. Nitrate, sulfate, sulfite, thiosulfate, and other chlorinated compounds were not used as electron acceptors. Sulfite had a strong inhibitory effect on growth and dechlorination. Alternate electron acceptors (e.g., fumarate or ferric iron) did not inhibit PCE dechlorination and were consumed concomitantly. The putative fumarate, PCE, and ferric iron reductases were induced by their respective substrates and were not constitutively present. Sulfide was required for growth. Both strains tolerated high concentrations of PCE, and dechlorination occurred in the presence of free-phase PCE (dense non-aqueous-phase liquids). Repeated growth with acetate and fumarate as substrates yielded a BB1 variant that had lost the ability to dechlorinate PCE. Due to the 16S rRNA gene sequence differences with the closest relatives and the unique phenotypic characteristics, we propose that the new isolates are members of a new species, Desulfuromonas michiganensis, within the Desulfuromonas cluster of the Geobacteraceae.
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Affiliation(s)
- Youlboong Sung
- School of Civil and Environmental Engineering. School of Biology, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0512, USA
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Sung Y, Ritalahti KM, Sanford RA, Urbance JW, Flynn SJ, Tiedje JM, Löffler FE. Characterization of two tetrachloroethene-reducing, acetate-oxidizing anaerobic bacteria and their description as Desulfuromonas michiganensis sp. nov. Appl Environ Microbiol 2003. [PMID: 12732573 DOI: 10.1128/aem.69.5.2964] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
Two tetrachlorethene (PCE)-dechlorinating populations, designated strains BB1 and BRS1, were isolated from pristine river sediment and chloroethene-contaminated aquifer material, respectively. PCE-to-cis-1,2-dichloroethene-dechlorinating activity could be transferred in defined basal salts medium with acetate as the electron donor and PCE as the electron acceptor. Taxonomic analysis based on 16S rRNA gene sequencing placed both isolates within the Desulfuromonas cluster in the delta subdivision of the Proteobacteria. PCE was dechlorinated at rates of at least 139 nmol min(-1) mg of protein(-1) at pH values between 7.0 and 7.5 and temperatures between 25 and 30 degrees C. Dechlorination also occurred at 10 degrees C. The electron donors that supported dechlorination included acetate, lactate, pyruvate, succinate, malate, and fumarate but not hydrogen, formate, ethanol, propionate, or sulfide. Growth occurred with malate or fumarate alone, whereas oxidation of the other electron donors depended strictly on the presence of fumarate, malate, ferric iron, sulfur, PCE, or TCE as an electron acceptor. Nitrate, sulfate, sulfite, thiosulfate, and other chlorinated compounds were not used as electron acceptors. Sulfite had a strong inhibitory effect on growth and dechlorination. Alternate electron acceptors (e.g., fumarate or ferric iron) did not inhibit PCE dechlorination and were consumed concomitantly. The putative fumarate, PCE, and ferric iron reductases were induced by their respective substrates and were not constitutively present. Sulfide was required for growth. Both strains tolerated high concentrations of PCE, and dechlorination occurred in the presence of free-phase PCE (dense non-aqueous-phase liquids). Repeated growth with acetate and fumarate as substrates yielded a BB1 variant that had lost the ability to dechlorinate PCE. Due to the 16S rRNA gene sequence differences with the closest relatives and the unique phenotypic characteristics, we propose that the new isolates are members of a new species, Desulfuromonas michiganensis, within the Desulfuromonas cluster of the Geobacteraceae.
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Affiliation(s)
- Youlboong Sung
- School of Civil and Environmental Engineering. School of Biology, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0512, USA
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He J, Ritalahti KM, Aiello MR, Löffler FE. Complete detoxification of vinyl chloride by an anaerobic enrichment culture and identification of the reductively dechlorinating population as a Dehalococcoides species. Appl Environ Microbiol 2003; 69:996-1003. [PMID: 12571022 PMCID: PMC143667 DOI: 10.1128/aem.69.2.996-1003.2003] [Citation(s) in RCA: 264] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A major obstacle in the implementation of the reductive dechlorination process at chloroethene-contaminated sites is the accumulation of the intermediate vinyl chloride (VC), a proven human carcinogen. To shed light on the microbiology involved in the final critical dechlorination step, a sediment-free, nonmethanogenic, VC-dechlorinating enrichment culture was derived from tetrachloroethene (PCE)-to-ethene-dechlorinating microcosms established with material from the chloroethene-contaminated Bachman Road site aquifer in Oscoda, Mich. After 40 consecutive transfers in defined, reduced mineral salts medium amended with VC, the culture lost the ability to use PCE and trichloroethene (TCE) as metabolic electron acceptors. PCE and TCE dechlorination occurred in the presence of VC, presumably in a cometabolic process. Enrichment cultures supplied with lactate or pyruvate as electron donor dechlorinated VC to ethene at rates up to 54 micromol liter(-1)day(-1), and dichloroethenes (DCEs) were dechlorinated at about 50% of this rate. The half-saturation constant (K(S)) for VC was 5.8 microM, which was about one-third lower than the concentrations determined for cis-DCE and trans-DCE. Similar VC dechlorination rates were observed at temperatures between 22 and 30 degrees C, and negligible dechlorination occurred at 4 and 35 degrees C. Reductive dechlorination in medium amended with ampicillin was strictly dependent on H(2) as electron donor. VC-dechlorinating cultures consumed H(2) to threshold concentrations of 0.12 ppm by volume. 16S rRNA gene-based tools identified a Dehalococcoides population, and Dehalococcoides-targeted quantitative real-time PCR confirmed VC-dependent growth of this population. These findings demonstrate that Dehalococcoides populations exist that use DCEs and VC but not PCE or TCE as metabolic electron acceptors.
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Affiliation(s)
- Jianzhong He
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0512, USA
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