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Lorah MM, Vogler E, Gebhardt FE, Graves D, Grabowski JF. Enhanced bioremediation of RDX and Co-Contaminants perchlorate and nitrate using an anaerobic dehalogenating consortium in a fractured rock aquifer. CHEMOSPHERE 2022; 294:133674. [PMID: 35065174 DOI: 10.1016/j.chemosphere.2022.133674] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/15/2022] [Accepted: 01/16/2022] [Indexed: 06/14/2023]
Abstract
The potential neurotoxic and carcinogenic effects of the explosives compound RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) on human health requires groundwater remediation strategies to meet low cleanup goals. Bioremediation of RDX is feasible through biostimulation of native microbes with an organic carbon donor but may be less efficient, or not occur at all, in the presence of the common co-contaminants perchlorate and nitrate. Laboratory tests compared biostimulation with bioaugmentation to achieve anaerobic degradation of RDX, perchlorate, and nitrate; a field pilot test was then conducted in a fractured rock aquifer with the selected bioaugmentation approach. Insignificant reduction of RDX, perchlorate, or nitrate was observed by the native microbes in microcosms, with or without biostimulation by addition of lactate. Tests of the RDX-degrading ability of the microbial consortium WBC-2, originally developed for dehalogenation of chlorinated volatile organic compounds, showed first-order biodegradation rate constants ranging from 0.57 to 0.90 per day (half-lives 1.2 to 0.80 days). WBC-2 sustained degradation without daughter product accumulation when repeatedly amended with RDX and lactate for a year. In microcosms with groundwater containing perchlorate and nitrate, RDX degradation began without delay when bioaugmented with 10% WBC-2. Slower RDX degradation occurred with 3% or 5% WBC-2 amendment, indicating a direct relation with cell density. Transient RDX daughter compounds included methylene dinitramine, MNX, and DNX. With WBC-2 amendment, nitrate concentrations immediately decreased to near or below detection, and perchlorate degradation occurred with half-lives of 25-34 days. Single-well injection tests with WBC-2 and lactate showed that the onset of RDX degradation coincided with the onset of sulfide production, which was affected by the initial perchlorate concentration. Biodegradation rates in the pilot injection tests agreed well with those measured in the microcosms. These results support bioaugmentation with an anaerobic culture as a remedial strategy for sites contaminated with RDX, nitrate, and perchlorate.
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Affiliation(s)
| | - Eric Vogler
- U.S. Geological Survey, Albuquerque, NM, USA.
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Effects of Perchlorate and Other Groundwater Inorganic Co-Contaminants on Aerobic RDX Degradation. Microorganisms 2022; 10:microorganisms10030663. [PMID: 35336238 PMCID: PMC8949498 DOI: 10.3390/microorganisms10030663] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/08/2022] [Accepted: 03/18/2022] [Indexed: 02/01/2023] Open
Abstract
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) pollution is accompanied by other co-contaminants, such as perchlorate and chlorates, which can retard biodegradation. The effects of perchlorate and chlorate on aerobic RDX degradation remain unclear. We hypothesized that they have a negative or no impact on aerobic RDX-degrading bacteria. We used three aerobic RDX-degrading strains—Rhodococcus strains YH1 and T7 and Gordonia YY1—to examine this hypothesis. The strains were exposed to perchlorate, chlorate, and nitrate as single components or in a mixture. Their growth, degradation activity, and gene expression were monitored. Strain-specific responses to the co-contaminants were observed: enhanced growth of strain YH1 and inhibition of strain T7. Vmax and Km of cytochrome P450 (XplA) in the presence of the co-contaminants were not significantly different from the control, suggesting no direct influence on cytochrome P450. Surprisingly, xplA expression increased fourfold in cultures pre-grown on RDX and, after washing, transferred to a medium containing only perchlorate. This culture did not grow, but xplA was translated and active, albeit at lower levels than in the control. We explained this observation as being due to nitrogen limitation in the culture and not due to perchlorate induction. Our results suggest that the aerobic strain YH1 is effective for aerobic remediation of RDX in groundwater.
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Khan MI, Yoo K, Kim S, Cheema SA, Bashir S, Park J. A Sporolactobacillus-, Clostridium-, and Paenibacillus- Dominant Microbial Consortium Improved Anaerobic RDX Detoxification by Starch Addition. J Microbiol Biotechnol 2020; 30:839-847. [PMID: 32160699 PMCID: PMC9728379 DOI: 10.4014/jmb.1910.10034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 03/05/2020] [Indexed: 12/15/2022]
Abstract
In the present study, an anaerobic microbial consortium for the degradation of hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX) was selectively enriched with the co-addition of RDX and starch under nitrogen-deficient conditions. Microbial growth and anaerobic RDX biodegradation were effectively enhanced by the co-addition of RDX and starch, which resulted in increased RDX biotransformation to nitroso derivatives at a greater specific degradation rate than those for previously reported anaerobic RDX-degrading bacteria (isolates). The accumulation of the most toxic RDX degradation intermediate (MNX [hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine]) was significantly reduced by starch addition, suggesting improved RDX detoxification by the co-addition of RDX and starch. The subsequent MiSeq sequencing that targeted the bacterial 16S rRNA gene revealed that the Sporolactobacillus, Clostridium, and Paenibacillus populations were involved in the enhanced anaerobic RDX degradation. These results suggest that these three bacterial populations are important for anaerobic RDX degradation and detoxification. The findings from this work imply that the Sporolactobacillus, Clostridium, and Paenibacillus dominant microbial consortium may be valuable for the development of bioremediation resources for RDX-contaminated environments.
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Affiliation(s)
- Muhammad Imran Khan
- Department of Civil and Environmental Engineering, College of Engineering, Yonsei University, Seoul 03722, Republic of Korea,Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan,Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research- UFZ, 0318 Leipzig, Germany
| | - Keunje Yoo
- Department of Civil and Environmental Engineering, College of Engineering, Yonsei University, Seoul 03722, Republic of Korea,Department of Environmental Engineering, College of Engineering, Korea Maritime and Ocean University, Busan 49112, Republic of Korea
| | - Seonghoon Kim
- Department of Civil and Environmental Engineering, College of Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Sardar Alam Cheema
- Department of Agronomy, University of Agriculture, Faisalabad 8040, Pakistan
| | - Safdar Bashir
- Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad 38040, Pakistan
| | - Joonhong Park
- Department of Civil and Environmental Engineering, College of Engineering, Yonsei University, Seoul 03722, Republic of Korea,Corresponding author Phone: +82-2-2123-7768 Fax: +82-2-312-5798 E-mail:
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Michalsen MM, King AS, Istok JD, Crocker FH, Fuller ME, Kucharzyk KH, Gander MJ. Spatially-distinct redox conditions and degradation rates following field-scale bioaugmentation for RDX-contaminated groundwater remediation. JOURNAL OF HAZARDOUS MATERIALS 2020; 387:121529. [PMID: 31911385 DOI: 10.1016/j.jhazmat.2019.121529] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/10/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
In situ bioaugmentation for cleanup of an hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-contaminated groundwater plume was recently demonstrated. Results of a forced-gradient, field-scale cell transport test with Gordonia sp. KTR9 and Pseudomonas fluorescens strain I-C cells (henceforth "KTR9" and "Strain I-C") showed these strains were transported 13 m downgradient over 1 month. Abundances of xplA and xenB genes, respective indicators of KTR9 and Strain I-C, approached injection well cell densities at 6 m downgradient, whereas gene abundances (and conservative tracer) had begun to increase at 13 m downgradient at test conclusion. In situ push-pull tests were subsequently completed to measure RDX degradation rates in the bioaugmented wells under ambient gradient conditions. Time-series monitoring of RDX, RDX end-products, conservative tracer, xplA and xenB gene copy numbers and XplA and XenB protein abundance were used to assess the efficacy of bioaugmentation and to estimate the apparent first-order RDX degradation rates during each test. A collective evaluation of redox conditions, RDX end-products, varied RDX degradation kinetics, and biomarkers indicated that Strain I-C and KTR9 rapidly degraded RDX. Results showed bioaugmentation is a viable technology for accelerating RDX cleanup in the demonstration site aquifer and may be applicable to other sites. Full-scale implementation considerations are discussed.
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Affiliation(s)
- M M Michalsen
- U.S. Army Engineer Research and Development Center, Environmental Laboratory, Vicksburg, MS 39180, United States.
| | - A S King
- U.S. Army Corps of Engineers, Seattle District, Seattle, WA 98134, United States
| | - J D Istok
- School of Civil and Construction Engineering, Oregon State University, Corvallis, OR 97331, United States
| | - F H Crocker
- U.S. Army Engineer Research and Development Center, Environmental Laboratory, Vicksburg, MS 39180, United States
| | - M E Fuller
- Aptim Federal Services, Lawrenceville, NJ 08648, United States
| | - K H Kucharzyk
- Battelle Memorial Institute, 505 King Ave, Columbus, OH, 43201, United States
| | - M J Gander
- Naval Facilities Engineering Command, Northwest, 1101 Tautog Circle, Silverdale, WA 98113, United States
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Collier JM, Chai B, Cole JR, Michalsen MM, Cupples AM. High throughput quantification of the functional genes associated with RDX biodegradation using the SmartChip real-time PCR system. Appl Microbiol Biotechnol 2019; 103:7161-7175. [PMID: 31352507 DOI: 10.1007/s00253-019-10022-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 07/08/2019] [Accepted: 07/09/2019] [Indexed: 02/06/2023]
Abstract
The explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a contaminant at many military sites. RDX bioremediation as a clean-up approach has been gaining popularity because of cost benefits compared to other methods. RDX biodegradation has primarily been linked to six functional genes (diaA, nfsI, pnrB, xenA, xenB, xplA). However, current methods for gene quantification have the risk of false negative results because of low theoretical primer coverage. To address this, the current study designed new primer sets using the EcoFunPrimer tool based on sequences collected by the Functional Gene Pipeline and Repository and these were verified based on residues and motifs. The primers were also designed to be compatible with the SmartChip Real-Time PCR system, a massively parallel singleplex PCR platform (high throughput qPCR), that enables quantitative gene analysis using 5,184 simultaneous reactions on a single chip with low volumes of reagents. This allows multiple genes and/or multiple primer sets for a single gene to be used with multiple samples. Following primer design, the six genes were quantified in RDX-contaminated groundwater (before and after biostimulation), RDX-contaminated sediment, and uncontaminated samples. The final 49 newly designed primer sets improved upon the theoretical coverage of published primer sets, and this corresponded to more detections in the environmental samples. All genes, except diaA, were detected in the environmental samples, with xenA and xenB being the most predominant. In the sediment samples, nfsI was the only gene detected. The new approach provides a more comprehensive tool for understanding RDX biodegradation potential at contaminated sites.
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Affiliation(s)
- J M Collier
- Department of Civil and Environmental Engineering, Michigan State University, A135, 1449 Engineering Research Court, East Lansing, MI, 48824, USA
| | - B Chai
- Department of Plant, Soil and Microbial Sciences, Plant and Soil Sciences Building, 1066 Bogue St., East Lansing, MI, 48824, USA
| | - J R Cole
- Department of Plant, Soil and Microbial Sciences, Plant and Soil Sciences Building, 1066 Bogue St., East Lansing, MI, 48824, USA
| | - M M Michalsen
- U.S. Army Engineer Research Development Center, 4735 E. Marginal Way S., Seattle, WA, 98134, USA
| | - Alison M Cupples
- Department of Civil and Environmental Engineering, Michigan State University, A135, 1449 Engineering Research Court, East Lansing, MI, 48824, USA.
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Effects of chitin and temperature on sub-Arctic soil microbial and fungal communities and biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4-dinitrotoluene (DNT). Biodegradation 2019; 30:415-431. [DOI: 10.1007/s10532-019-09884-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 06/19/2019] [Indexed: 02/06/2023]
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Rylott EL, Bruce NC. Right on target: using plants and microbes to remediate explosives. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION 2019; 21:1051-1064. [PMID: 31056922 DOI: 10.1080/15226514.2019.1606783] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
While the immediate effect of explosives in armed conflicts is frequently in the public eye, until recently, the insidious, longer-term corollaries of these toxic compounds in the environment have gone largely unnoticed. Now, increased public awareness and concern are factors behind calls for more effective remediation solutions to these global pollutants. Scientists have been working on bioremediation projects in this area for several decades, characterizing genes, biochemical detoxification pathways, and field-applicable plant species. This review covers the progress made in understanding the fundamental biochemistry behind the detoxification of explosives, including new shock-insensitive explosive compounds; how field-relevant plant species have been characterized and genetically engineered; and the major roles that endophytic and rhizospheric microorganisms play in the detoxification of organic pollutants such as explosives.
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Affiliation(s)
- Elizabeth L Rylott
- Centre for Novel Agricultural Products, Department of Biology, University of York , York , UK
| | - Neil C Bruce
- Centre for Novel Agricultural Products, Department of Biology, University of York , York , UK
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Sowani H, Kulkarni M, Zinjarde S. Harnessing the catabolic versatility of Gordonia species for detoxifying pollutants. Biotechnol Adv 2019; 37:382-402. [DOI: 10.1016/j.biotechadv.2019.02.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 01/12/2019] [Accepted: 02/11/2019] [Indexed: 11/26/2022]
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