1
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Botti A, Musmeci E, Matturro B, Vanzetto G, Bosticco C, Negroni A, Rossetti S, Fava F, Biagi E, Zanaroli G. Chemical-physical parameters and microbial community changes induced by electrodes polarization inhibit PCB dechlorination in a marine sediment. JOURNAL OF HAZARDOUS MATERIALS 2024; 469:133878. [PMID: 38447365 DOI: 10.1016/j.jhazmat.2024.133878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 01/30/2024] [Accepted: 02/22/2024] [Indexed: 03/08/2024]
Abstract
Microbial reductive dechlorination of organohalogenated pollutants is often limited by the scarcity of electron donors, that can be overcome with microbial electrochemical technologies (METs). In this study, polarized electrodes buried in marine sediment microcosms were investigated to stimulate PCB reductive dechlorination under potentiostatic (-0.7 V vs Ag/AgCl) and galvanostatic conditions (0.025 mA·cm-2-0.05 mA·cm-2), using graphite rod as cathode and iron plate as sacrificial anode. A single circuit and a novel two antiparallel circuits configuration (2AP) were investigated. Single circuit polarization impacted the sediment pH and redox potential (ORP) proportionally to the intensity of the electrical input and inhibited PCB reductive dechlorination. The effects on the sediment's pH and ORP, along with the inhibition of PCB reductive dechlorination, were mitigated in the 2AP system. Electrodes polarization stimulated sulfate-reduction and promoted the enrichment of bacterial clades potentially involved in sulfate-reduction as well as in sulfur oxidation. This suggested the electrons provided were consumed by competitors of organohalide respiring bacteria and specifically sequestered by sulfur cycling, which may represent the main factor limiting the applicability of METs for stimulating PCB reductive dechlorination in marine sediments.
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Affiliation(s)
- Alberto Botti
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Eliana Musmeci
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Bruna Matturro
- Water Research Institute (IRSA), National Research Council (CNR), 00010 Montelibretti, Italy; National Biodiversity Future Center, 90133 Palermo, Italy
| | - Giampietro Vanzetto
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Caterina Bosticco
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Andrea Negroni
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Simona Rossetti
- Water Research Institute (IRSA), National Research Council (CNR), 00010 Montelibretti, Italy
| | - Fabio Fava
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Elena Biagi
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy
| | - Giulio Zanaroli
- Dept. of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum University of Bologna, Via Terracini 28, 40131 Bologna, Italy.
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2
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Xu Y, Wang Y, Zheng A, Yuan Y, Xu L, Tang Y, Qin Q. Efficient biostimulation of microbial dechlorination of polychlorinated biphenyls by acetate and lactate under nitrate reducing conditions: Insights into dechlorination pathways and functional genes. JOURNAL OF HAZARDOUS MATERIALS 2024; 468:133775. [PMID: 38367444 DOI: 10.1016/j.jhazmat.2024.133775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 02/04/2024] [Accepted: 02/09/2024] [Indexed: 02/19/2024]
Abstract
Microbial-catalyzed reductive dechlorination of polychlorinated biphenyls (PCBs) is largely affected by the indigenous sediment geochemical properties. In this study, the effects of nitrate on PCB dechlorination and microbial community structures were first investigated in Taihu Lake sediment microcosms. And biostimulation study was attempted supplementing acetate/lactate. PCB dechlorination was apparently inhibited under nitrate-reducing conditions. Lower PCB dechlorination rate and less PCB dechlorination extent were observed in nitrate amended sediment microcosms (T-N) than those in non-nitrate amended microcosms (T-1) during 66 weeks of incubation. The total PCB mass reduction in T-N was 17.6% lower than that in T-1. The flanked-para dechlorination was completely inhibited, while the ortho-flanked meta dechlorination was only partially inhibited in T-N. The 7.5 mM of acetate/lactate supplementation recovered PCB dechlorination by resuming ortho-flanked meta dechlorination. Repeated additions of lactate showed more effective biostimulation than acetate. Phylum Chloroflexi, containing most known PCB dechlorinators, was found to play a vital role on stability of the network structures. In T-N, putative dechlorinating Chloroflexi, Dehalococcoides and RDase genes rdh12, pcbA4, pcbA5 all declined. With acetate/lactate supplementation, Dehalococcoides grew by 1-2 orders of magnitude and rdh12, pcbA4, pcbA5 increased by 1-3 orders of magnitude. At Week 66, parent PCBs declined by 86.4% and 80.9% respectively in T-N-LA and T-N-AC compared to 69.9% in T-N. These findings provide insights into acetate/lactate biostimulation as a cost-effective approach for treating PCB contaminated sediments undergoing nitrate inhibition.
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Affiliation(s)
- Yan Xu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China.
| | - Ying Wang
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - An Zheng
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yaping Yuan
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Lei Xu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yanqiang Tang
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Qingdong Qin
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu 210096, China
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3
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Xu L, Tang Y, Liu S, Chen X, Wang Y, Liu Z, Qin Q, Fu D, Xu Y. Short-chain fatty acids facilitated long-term dechlorination of PCBs in Taihu Lake sediment microcosms: Evidence from PCB congener and microbial community analyses. CHEMOSPHERE 2023; 340:139935. [PMID: 37619750 DOI: 10.1016/j.chemosphere.2023.139935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 07/12/2023] [Accepted: 08/21/2023] [Indexed: 08/26/2023]
Abstract
Microbial reductive dechlorination hosts great promise as an in situ bioremediation strategy for polychlorinated biphenyls (PCBs) contamination. However, the slow dechlorination in sediments limits natural attenuation. Short-chain fatty acids, as preferred carbon sources and electron donors for dechlorinating microorganisms, might stimulate PCB dechlorination. Herein, two sets of short-chain fatty acids, sole acetate and a fatty acid mixture (acetate, propionate, and butyrate), were amended periodically into Taihu Lake (China) sediment microcosms containing nine PCB congeners (PCB5, 12, 64, 71, 105, 114, 149, 153, and 170) after 24 weeks of incubation. Short-chain fatty acids facilitated the long-term PCB dechlorination and the promoting effect of the fatty acid mixture compared favorably with that of sole acetate. By the end of 108 weeks, the total PCB mass concentrations in acetate amended and fatty acid mixture amended microcosms significantly declined by 7.6% and 10.3% compared with non-amended microcosms (P < 0.05), respectively. Short-chain fatty acids selectively favored the removal of flanked meta and single-flanked para chlorines. Notably, a rare ortho dechlorination pathway, PCB25 (24-3-CB) to PCB13 (3-4-CB), was enhanced. Supplementary fatty acids significantly increased reductive dehalogenases (RDase) gene pcbA5 instead of improving the growth of Dehalococcoides. These findings highlight the merits of low cost short-chain fatty acids on in situ biostimulation in treating PCBs contamination.
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Affiliation(s)
- Lei Xu
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Yanqiang Tang
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Sha Liu
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Xi Chen
- Water Affairs Bureau of Nanjing Pukou District, Nanjing, 211899, China
| | - Ying Wang
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Zheming Liu
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Qingdong Qin
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Dafang Fu
- School of Civil Engineering, Southeast University, Nanjing, 210096, China
| | - Yan Xu
- School of Civil Engineering, Southeast University, Nanjing, 210096, China.
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4
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Cheng YH, Chang SC, Lai YL, Hu CC. Microbiome reengineering by four environmental factors for the rapid biodegradation of trichloroethylene. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 326:116658. [PMID: 36399881 DOI: 10.1016/j.jenvman.2022.116658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 10/21/2022] [Accepted: 10/27/2022] [Indexed: 06/16/2023]
Abstract
Trichloroethylene (TCE) was once a widely applied industrial solvent, but is now an infamous contaminant in groundwater. Although anaerobic reductive dechlorination is considered a greener remediation approach, the accumulation of toxic intermediates, such as vinyl chloride (VC), and a longer remediation period are highly concerning. Biostimulation and bioaugmentation have been developed to solve these problems. The former method may not be effective, and the latter may introduce foreign genes. Here, we propose a new approach by applying environmental stresses to reshape the indigenous microbiome. In this study, by using the Taguchi method, the effects of heating, pH, salinity, and desiccation were systematically examined. The optimum conditions were defined as 50 °C, pH 9, 3.50% salinity (w/v), and 21% volumetric water content (θW). The top performing group, G7, can complete the conversion of 11.81 mg/L TCE into ethene in 3.0 days with a 1.23% abundance of Dehalococcoides mccartyi 195 (Dhc 195). Redundancy analysis confirmed that temperature and salinity were the predominant factors in reorganizing the microbiomes. The microbiome structure and its effectiveness can last for at least 90 d. The repetitive selection conditions and sustainable degradation capability strongly supported that microbiome reengineering is feasible for the rapid bioremediation of TCE-contaminated environmental matrices.
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Affiliation(s)
- Yu-Hsuan Cheng
- Department of Environmental Engineering, National Chung Hsing University, No. 145, Xingda Road, Taichung, 40227, Taiwan
| | - Shu-Chi Chang
- Department of Environmental Engineering, National Chung Hsing University, No. 145, Xingda Road, Taichung, 40227, Taiwan.
| | - Yan-Lin Lai
- Graduate Institute of Biotechnology, National Chung Hsing University, No. 145, Xingda Road, Taichung, 40227, Taiwan
| | - Chung-Chi Hu
- Graduate Institute of Biotechnology, National Chung Hsing University, No. 145, Xingda Road, Taichung, 40227, Taiwan
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5
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Ewald JM, Schnoor JL, Mattes TE. Combined read- and assembly-based metagenomics to reconstruct a Dehalococcoides mccartyi genome from PCB-contaminated sediments and evaluate functional differences among organohalide-respiring consortia in the presence of different halogenated contaminants. FEMS Microbiol Ecol 2022; 98:6602352. [PMID: 35665806 DOI: 10.1093/femsec/fiac067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/27/2022] [Accepted: 05/31/2022] [Indexed: 11/12/2022] Open
Abstract
Microbial communities that support respiration of halogenated organic contaminants by Dehalococcoides sp. facilitate full-scale bioremediation of chlorinated ethenes and demonstrate the potential to aid in bioremediation of halogenated aromatics like polychlorinated biphenyls (PCBs). However, it remains unclear if Dehalococcoides-containing microbial community dynamics observed in sediment-free systems quantitatively resemble that of sediment environments. To evaluate that possibility we assembled, annotated, and analyzed a Dehalococcoides sp. metagenome-assembled genome (MAG) from PCB-contaminated sediments. Phylogenetic analysis of reductive dehalogenase gene (rdhA) sequences within the MAG revealed that pcbA1 and pcbA4/5-like rdhA were absent, while several candidate PCB dehalogenase genes and potentially novel rdhA sequences were identified. Using a compositional comparative metagenomics approach, we quantified Dehalococcoides-containing microbial community structure shifts in response to halogenated organics and the presence of sediments. Functional level analysis revealed significantly greater abundances of genes associated with cobamide remodeling and horizontal gene transfer in tetrachloroethene-fed cultures as compared to halogenated aromatic-exposed consortia with or without sediments, despite little evidence of statistically significant differences in microbial community taxonomic structure. Our findings support the use of a generalizable comparative metagenomics workflow to evaluate Dehalococcoides-containing consortia in sediments and sediment-free environments to eludicate functions and microbial interactions that facilitate bioremediation of halogenated organic contaminants.
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Affiliation(s)
- Jessica M Ewald
- Department of Civil and Environmental Engineering, 4105 Seamans Center, University of Iowa, Iowa City, IA, 52242, USA
| | - Jerald L Schnoor
- Department of Civil and Environmental Engineering, 4105 Seamans Center, University of Iowa, Iowa City, IA, 52242, USA
| | - Timothy E Mattes
- Department of Civil and Environmental Engineering, 4105 Seamans Center, University of Iowa, Iowa City, IA, 52242, USA
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6
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Xu G, Zhang N, Zhao X, Chen C, Zhang C, He J. Offshore Marine Sediment Microbiota Respire Structurally Distinct Organohalide Pollutants. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:3065-3075. [PMID: 35187933 DOI: 10.1021/acs.est.1c06680] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Marine sediments are a major sink of organohalide pollutants, but the potential for offshore marine microbiota to transform these pollutants remains underexplored. Here, we report dehalogenation of diverse organohalide pollutants by offshore marine microbiota. Dechlorination of polychlorinated biphenyls (PCBs) was observed in four marine sediment microcosms, which was positively correlated with in situ PCB contamination. Three distinct enrichment cultures were enriched from these PCB-dechlorinating microcosms using tetrachloroethene (PCE) as the sole organohalide. All enrichment cultures also dehalogenated polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA), and 2,4,6-trichlorophenol (2,4,6-TCP). Particularly, two enrichments completely debrominated penta-BDEs, the first observation of complete debromination of penta-BDEs in marine cultures. Multiple Dehalococcoides and uncultivated Dehalococcoidia were identified in the initial sediment microcosms, but only Dehalococcoides was dominant in all enrichments. Transcription of a gene encoding a PcbA5-like reductive dehalogenase (RDase) was observed during dehalogenation of different organohalides in each enrichment culture. When induced by a single organohalide substrate, the PcbA5-like RDase dehalogenated all tested organohalides (PCE, PCBs, PBDEs, TBBPA, and 2,4,6-TCP) in in vitro tests, suggesting its involvement in dehalogenation of structurally distinct organohalides. Our results demonstrate the versatile dehalogenation capacity of marine Dehalococcoidia and contribute to a better understanding of the fate of these pollutants in marine systems.
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Affiliation(s)
- Guofang Xu
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, Singapore 117576, Singapore
- NUS Graduate School─Integrative Sciences and Engineering Programme (ISEP), National University of Singapore, Singapore 119077, Singapore
| | - Ning Zhang
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, Singapore 117576, Singapore
- Institute of Marine Biology and Pharmacology, Ocean College, Zhejiang University, Zhoushan, Zhejiang 316021, China
- College of Chemical Engineering and Pharmacy, Henan University of Science and Technology, Luoyang, Henan 471003, China
| | - Xuejie Zhao
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, Singapore 117576, Singapore
| | - Chen Chen
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, Singapore 117576, Singapore
| | - Chunfang Zhang
- Institute of Marine Biology and Pharmacology, Ocean College, Zhejiang University, Zhoushan, Zhejiang 316021, China
| | - Jianzhong He
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, Singapore 117576, Singapore
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7
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Xu L, Liu S, Tang Y, Han X, Wang Y, Fu D, Qin Q, Xu Y. Long-Term Dechlorination of Polychlorinated Biphenyls (PCBs) in Taihu Lake Sediment Microcosms: Identification of New Pathways, PCB-Driven Shifts of Microbial Communities, and Insights into Dechlorination Potential. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:938-950. [PMID: 34958198 DOI: 10.1021/acs.est.1c06057] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Microbial reductive dechlorination of polychlorinated biphenyls (PCBs) is regarded as an alternative approach for in situ remediation and detoxification in the environment. To better understand the process of PCB dechlorination in freshwater lake sediment, a long-term (108 weeks) dechlorination study was performed in Taihu Lake sediment microcosms with nine parent PCB congeners (PCB5, 12, 64, 71, 105, 114, 149, 153, and 170). Within 108 weeks, the total PCBs declined by 32.8%, while parent PCBs declined by 84.8%. PCB dechlorinators preferred to attack meta- and para-chlorines, principally para-flanked meta and single-flanked para chlorines. A total of 58 dechlorination pathways were observed, and 20 of them were not in 8 processes, suggesting the broad spectrum of PCB dechlorination in the environment. Rare ortho dechlorination was confirmed to target the unflanked ortho chlorine, indicating a potential for complete dechlorination. PCBs drove the shifts of the microbial community structures, and putative dechlorinating bacteria were growth-linked to PCB dechlorination. The distinct jump of RDase genes ardA, rdh12, pcbA4, and pcbA5 was found to be consistent with the commencement of dechlorination. The maintained high level of putative dechlorinating phylum Chloroflexi (including Dehalococcoides and o-17/DF-1), genus Dehalococcoides, and four RDase genes at the end of incubation revealed the long-term dechlorination potential. This work provided insights into dechlorination potential for long-term remediation strategies at PCB-contaminated sites.
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Affiliation(s)
- Lei Xu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Sha Liu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Yanqiang Tang
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Xuexin Han
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Ying Wang
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Dafang Fu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Qingdong Qin
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
| | - Yan Xu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing 210096, Jiangsu, China
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8
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Recent advances in the biodegradation of polychlorinated biphenyls. World J Microbiol Biotechnol 2020; 36:145. [PMID: 32862310 DOI: 10.1007/s11274-020-02922-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 08/22/2020] [Indexed: 12/22/2022]
Abstract
Polychlorinated biphenyls (PCBs) are typical lasting organic pollutants. Persistence and recalcitrance to biodegradation of PCBs have hampered the transformation of PCB congeners from the environment. Biological transformation of polychlorinated biphenyls could take place through anaerobic dechlorination, aerobic microbial degradation, and a combination of transformation of anaerobic dechlorination and aerobic degradation. Under anaerobic conditions, microbial dechlorination is an important degradation mode for PCBs, especially high-chlorinated congeners. The low-chlorinated compounds formed after reductive dechlorination could be further aerobically degraded and completely mineralized. This paper reviews the recent advances in biological degradation of PCBs, introduces the functional bacteria and enzymes involved in the anaerobic and aerobic degradation of PCBs, and discusses the synergistic action of anaerobic reduction and aerobic degradation. In addition, the different ways to the microbial remediation of PCBs-contaminated environments are discussed. This review provides a theoretical foundation and practical basis to use PCBs-degrading microorganisms for bioremediation.
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9
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Matturro B, Mascolo G, Rossetti S. Microbiome changes and oxidative capability of an anaerobic PCB dechlorinating enrichment culture after oxygen exposure. N Biotechnol 2020; 56:96-102. [DOI: 10.1016/j.nbt.2019.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 12/18/2019] [Accepted: 12/22/2019] [Indexed: 12/16/2022]
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10
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Ewald JM, Humes SV, Martinez A, Schnoor JL, Mattes TE. Growth of Dehalococcoides spp. and increased abundance of reductive dehalogenase genes in anaerobic PCB-contaminated sediment microcosms. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:8846-8858. [PMID: 31209752 PMCID: PMC6918016 DOI: 10.1007/s11356-019-05571-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 05/24/2019] [Indexed: 06/09/2023]
Abstract
Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious risk to human and environmental health. One promising strategy to remediate PCB-contaminated sediments utilizes organohalide-respiring bacteria (OHRB) that dechlorinate PCBs.However, functional genes that act as biomarkers for PCB dechlorination processes (i.e., reductive dehalogenase genes) are poorly understood. Here, we developed anaerobic sediment microcosms that harbor an OHRB community dominated by the genus Dehalococcoides. During the 430-day microcosm incubation, Dehalococcoides 16S rRNA sequences increased two orders of magnitude to 107 copies/g of sediment, and at the same time, PCB118 decreased by as much as 70%. In addition, the OHRB community dechlorinated a range of penta- and tetra-chlorinated PCB congeners including PCBs 66, 70 + 74 + 76, 95, 90 + 101, and PCB110 without exogenous electron donor. We quantified candidate reductive dehalogenase (RDase) genes over a 430-day incubation period and found rd14, a reductive dehalogenase that belongs to Dehalococcoides mccartyi strain CG5, was enriched to 107 copies/g of sediment. At the same time, pcbA5 was enriched to only 105 copies/g of sediment. A survey for additional RDase genes revealed sequences similar to strain CG5's rd4 and rd8. In addition to demonstrating the PCB dechlorination potential of native microbial communities in contaminated freshwater sediments, our results suggest candidate functional genes with previously unexplored potential could serve as biomarkers of PCB dechlorination processes.
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Affiliation(s)
- Jessica M Ewald
- Department of Civil and Environmental Engineering, IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, 52242, USA
| | - Shelby V Humes
- Department of Civil and Environmental Engineering, IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, 52242, USA
| | - Andres Martinez
- Department of Civil and Environmental Engineering, IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, 52242, USA
| | - Jerald L Schnoor
- Department of Civil and Environmental Engineering, IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, 52242, USA
| | - Timothy E Mattes
- Department of Civil and Environmental Engineering, IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, IA, 52242, USA.
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11
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Ni J, Liu Y, Shen C, Chen D, Xin Y, Liu Q. Bioinformatics, bacterial expression and enzyme activity analyses of dichloromethane dehalogenase from Methylobacterium rhodesianum H13. BIOTECHNOL BIOTEC EQ 2020. [DOI: 10.1080/13102818.2020.1818622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Affiliation(s)
- Jianguo Ni
- Department of Environmental Engineering, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou, Zhejiang, PR China
- Department of Linpu Environmental Protection, Hangzhou Ecological Environment Bureau of Xiaoshan Branch, Hangzhou, Zhejiang, PR China
| | - Ying Liu
- Department of Environmental Engineering, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou, Zhejiang, PR China
| | - Chenjia Shen
- Department of Environmental Engineering, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou, Zhejiang, PR China
| | - Dongzhi Chen
- Department of Environmental Engineering, College of Environment, Zhejiang University of Technology, Hangzhou, Zhejiang, PR China
| | - Yueyong Xin
- Department of Environmental Engineering, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou, Zhejiang, PR China
| | - Qi Liu
- Department of Environmental Engineering, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou, Zhejiang, PR China
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12
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Xu Y, Gregory KB, VanBriesen JM. Reduction in sulfate inhibition of microbial dechlorination of polychlorinated biphenyls in Hudson and Grasse River sediments through fatty acid supplementation. CHEMOSPHERE 2019; 233:81-91. [PMID: 31170587 DOI: 10.1016/j.chemosphere.2019.05.211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 06/09/2023]
Abstract
Microbial dechlorination of polychlorinated biphenyls (PCBs) in aquatic sediments may reduce the need for dredging for remediation. To better understand this biotransformation route under different geochemical conditions, the influence of sulfate on dechlorination in sediments from the Hudson River and the Grasse River spiked with two PCB mixtures (PCB 5/12, 64/71, 105/114 and 149/153/170 in Mixture 1 and PCB 5/12, 64/71, 82/97/99, 144/170 in Mixture 2) was investigated. The results showed that PCB dechlorination was partially inhibited in the sulfate-amended sediment microcosms. The rate, extent and preference of dechlorination were mainly controlled by the indigenous differences (sulfate, carbon content etc.) in sediment, but also affected by the PCB mixture composition. An increase of Dehalococcoides 16S rRNA genes coincided with the resumption of dechlorination. Dechlorination preferences were identified using a modified dechlorination pathway analysis approach. The low carbon content and high background sulfate Hudson sediment exhibited more para dechlorination targeting flanked para chlorines. The high carbon content and low background sulfate Grasse sediment preferentially removed more para-flanked meta chlorines than flanked para chlorines. The supplementation of fatty acids (acetate or a mixture of acetate, propionate and butyrate) dramatically increased PCB dechlorination in the Grasse sediment by resuming ortho-flanked meta dechlorination. Rare ortho removals were found in the Grasse sediment after adding fatty acids. This study suggests that supplementary fatty acids might be used to stimulate PCB dechlorination under sulfate reducing conditions, but the effectiveness largely depends on sediment geochemistry.
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Affiliation(s)
- Yan Xu
- Department of Municipal Engineering, School of Civil Engineering, Southeast University, Nanjing, Jiangsu, 210096, China; Department of Civil and Environmental Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, 15213-3890, PA, United States.
| | - Kelvin B Gregory
- Department of Civil and Environmental Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, 15213-3890, PA, United States.
| | - Jeanne M VanBriesen
- Department of Civil and Environmental Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, 15213-3890, PA, United States.
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Wei K, Yin H, Peng H, Lu G, Dang Z. Bioremediation of triphenyl phosphate in river water microcosms: Proteome alteration of Brevibacillus brevis and cytotoxicity assessments. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 649:563-570. [PMID: 30176467 DOI: 10.1016/j.scitotenv.2018.08.342] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 08/24/2018] [Accepted: 08/24/2018] [Indexed: 06/08/2023]
Abstract
Triphenyl phosphate (TPHP), an organophosphate flame retardant, was detected in river water samples collected from an electronic waste recycling area in Guiyu, Southern China. The concentrations of TPHP ranged from not detected to 347.2 ng/L, with an average of 138.8 ng/L. The bioaugmentation potential of Brevibacillus brevis on TPHP biodegradation by aerobic microcosms contained in river water from Guiyu was assessed. The results showed that TPHP degradation efficiency was significantly improved to 97.9% by bioaugmentation with B. brevis after 96 h incubation. A total of 182 significantly changed proteins in B. brevis were identified and quantified by isobaric tags for relative and absolute quantification (iTRAQ) in response to TPHP stress. The differentially expressed proteins were mainly associated with energy metabolism, lipid metabolism, cell wall biosynthesis, amino acid transport, and metabolism. The identification that proteins of B. brevis respond to TPHP existence provides novel insights into biodegradation mechanisms of bacteria under environmental stress. Additionally, cytotoxicity assays indicated that the degrading intermediates of TPHP, namely diphenyl phosphate and phenyl phosphate, were less cytotoxic to human HepG2 cells compared with TPHP. Collectively, these findings suggest that aerobic bioaugmentation with degrading microorganisms is a potential strategy for in situ treatment of TPHP-contaminated sites.
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Affiliation(s)
- Kun Wei
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem, Restoration in Industry Clusters, Guangdong Provincial Engineering and Technology, Research Center for Environxmental Risk Prevention and Emergency Disposal, School of Environment and Energy, South China University of Technology, Guangzhou 510006, Guangdong, PR China
| | - Hua Yin
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem, Restoration in Industry Clusters, Guangdong Provincial Engineering and Technology, Research Center for Environxmental Risk Prevention and Emergency Disposal, School of Environment and Energy, South China University of Technology, Guangzhou 510006, Guangdong, PR China.
| | - Hui Peng
- Department of Chemistry, Jinan University, Guangzhou 510632, Guangdong, PR China
| | - Guining Lu
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem, Restoration in Industry Clusters, Guangdong Provincial Engineering and Technology, Research Center for Environxmental Risk Prevention and Emergency Disposal, School of Environment and Energy, South China University of Technology, Guangzhou 510006, Guangdong, PR China
| | - Zhi Dang
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem, Restoration in Industry Clusters, Guangdong Provincial Engineering and Technology, Research Center for Environxmental Risk Prevention and Emergency Disposal, School of Environment and Energy, South China University of Technology, Guangzhou 510006, Guangdong, PR China
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14
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Polychlorinated Biphenyls (PCBs): Environmental Fate, Challenges and Bioremediation. MICROORGANISMS FOR SUSTAINABILITY 2019. [DOI: 10.1007/978-981-13-7462-3_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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15
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Wang YF, Zhu HW, Wang Y, Zhang XL, Tam NFY. Diversity and Dynamics of Microbial Community Structure in Different Mangrove, Marine and Freshwater Sediments During Anaerobic Debromination of PBDEs. Front Microbiol 2018; 9:952. [PMID: 29867858 PMCID: PMC5962692 DOI: 10.3389/fmicb.2018.00952] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 04/24/2018] [Indexed: 01/11/2023] Open
Abstract
Little is known about the diversity and succession of indigenous microbial community during debromination of polybrominated diphenyl ethers (PBDEs). This study examined the diversity and dynamics of microbial community structure in eight saline (mangrove and marine) and freshwater sediment microcosms exhibiting different debrominating capabilities for hexa-BDE 153, a common congener in sediments, using terminal restriction fragment length polymorphism (T-RFLP) and clone library analyses. The results showed that microbial community structure greatly differed between the saline and freshwater microcosms, likely leading to distinct variations in their debrominating capabilities and pathways. Higher relative abundances of Chloroflexi and Deltaproteobacteria succeed by Alphaproteobacteria and Betaproteobacteria were detected in the two mangrove microcosms with the fastest debrominating capabilities mainly via para pathway, respectively; the dominance of Alphaproteobacteria resulted in less accumulation of tetra-BDEs and more complete debromination of lower brominated congeners (from di- to tetra-BDEs). Meanwhile, the shifts in both microbial community structure and PBDE profiles were relatively small in the less efficient freshwater microcosms, with relatively more ortho and meta brominated products of BDE-153 resulted. Coincidently, one of the freshwater microcosms showed sudden increases of Chloroflexi and Deltaproteobacteria by the end of incubation, which synchronized with the increase in the removal rate of BDE-153. The significant relationship between microbial community structure and PBDEs was confirmed by redundancy analysis (18.7% of total variance explained, P = 0.002). However, the relative abundance of the well-known dechlorinator Dehalococcoides showed no clear correlation with the debrominating capability across different microcosms. These findings shed light in the significance of microbial community network in different saline environments on enhancement of PBDE intrinsic debromination.
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Affiliation(s)
- Ya Fen Wang
- Laboratory of Basin Hydrology and Wetland Eco-restoration, School of Environmental Studies, China University of Geosciences, Wuhan, China.,Department of Biology and Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - Hao Wen Zhu
- Department of Biology and Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - Ying Wang
- Department of Biology and Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong
| | - Xiang Ling Zhang
- School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan, China
| | - Nora Fung Yee Tam
- Department of Biology and Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong.,State Key Laboratory in Marine Pollution, City University of Hong Kong, Kowloon Tong, Hong Kong
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Nijenhuis I, Stollberg R, Lechner U. Anaerobic microbial dehalogenation and its key players in the contaminated Bitterfeld-Wolfen megasite. FEMS Microbiol Ecol 2018; 94:4828323. [PMID: 29385441 DOI: 10.1093/femsec/fiy012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 01/25/2018] [Indexed: 11/14/2022] Open
Abstract
The megasite Bitterfeld-Wolfen is highly contaminated as a result of accidents and because of dumping of wastes from local chemical industries in the last century. A variety of contaminants including chlorinated ethenes and benzenes, hexachlorohexanes and chlorinated dioxins can still be found in the groundwater and (river) sediments. Investigations of the in situ microbial transformation of organohalides have been performed only over the last two decades at this megasite. In this review, we summarise the research on the activity of anaerobic dehalogenating bacteria at the field site in Bitterfeld-Wolfen, focusing on chlorinated ethenes, monochlorobenzene and chlorinated dioxins. Various methods and concepts were applied including ex situ cultivation and isolation, and in situ analysis of hydrochemical parameters, compound-specific stable isotope analysis of contaminants, 13C-tracer studies and molecular markers. Overall, biotransformation of organohalides is ongoing at the field site and Dehalococcoides mccartyi species play an important role in the detoxification process in the Bitterfeld-Wolfen region.
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Affiliation(s)
- Ivonne Nijenhuis
- Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Reiner Stollberg
- Department of Groundwater Remediation, Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
| | - Ute Lechner
- Institute of Biology/Microbiology Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle, Germany
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17
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Matturro B, Frascadore E, Rossetti S. High-throughput sequencing revealed novel Dehalococcoidia in dechlorinating microbial enrichments from PCB-contaminated marine sediments. FEMS Microbiol Ecol 2018; 93:4443194. [PMID: 29040506 DOI: 10.1093/femsec/fix134] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 10/10/2017] [Indexed: 01/07/2023] Open
Abstract
In this study, six PCE-to-ethene dechlorinating cultures, fed with a fermentable substrate (lactate) or hydrogen as electron donor, were obtained from PCB and PCE dechlorinating microcosms constructed with PCB-contaminated marine sediments. A novel Chloroflexi member (OTU-DIS1) affiliated to Dehalococcoidales Incertae Sedis, only distantly related to known dechlorinating bacteria, dominated the enrichment cultures (up to 86% of total OTUs). Sulfate-, thiosulfate- and sulfur-reducing bacteria affiliated to genera Desulfobacter, Dethiosulfatibacter and Desulfuromusa were also found to lesser extent. Remarkably, tceA, vcrA and the bifunctional PCE/PCB dehalogenase genes pcbA1, pcbA4 and pcbA5 were found in all dechlorinating microbial enrichments indicating the coexistence of different Dehalococcoides mccartyi strains. The reductive dechlorination rate in each culture remained unvaried over long-term operation (≈ 30 months) and ranged between 0.85 and 0.97 mmol Cl-1 released L-1 d-1 in the lactate-fed microbial enrichments and between 0.66 and 0.85 mmol Cl-1 released L-1 d-1 in the H2-fed microbial enrichments. Overall, this study highlights the presence of yet unexplored biodiversity in PCBs contaminated marine sediments and indicates these environments as promising sources of novel organohalide-respiring bacteria.
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Affiliation(s)
- Bruna Matturro
- Water Research Institute, IRSA-CNR, Via Salaria km 29,300, 00015 Monterotondo (RM), Italy
| | - Emanuela Frascadore
- Water Research Institute, IRSA-CNR, Via Salaria km 29,300, 00015 Monterotondo (RM), Italy
| | - Simona Rossetti
- Water Research Institute, IRSA-CNR, Via Salaria km 29,300, 00015 Monterotondo (RM), Italy
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Nuzzo A, Negroni A, Zanaroli G, Fava F. Identification of two organohalide-respiring Dehalococcoidia associated to different dechlorination activities in PCB-impacted marine sediments. Microb Cell Fact 2017; 16:127. [PMID: 28738864 PMCID: PMC5525228 DOI: 10.1186/s12934-017-0743-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 07/14/2017] [Indexed: 01/02/2023] Open
Abstract
Background Microbial reductive dechlorination of polychlorinated biphenyls (PCBs) plays a major role in detoxifying anoxic contaminated freshwater and marine sediments from PCBs. Known members of the phylum Chloroflexi are typically responsible for this activity in freshwater sediments, whereas less is known about the microorganisms responsible for this activity in marine sediments. PCB-respiring activities were detected in PCB-impacted marine sediments of the Venice Lagoon. The aim of this work was to identify the indigenous organohalide-respiring microorganisms in such environments and assess their dechlorination specificity against spiked Aroclor™ 1254 PCBs under laboratory conditions resembling the in situ biogeochemistry. Results High PCB dechlorination activities (from 150 ± 7 to 380 ± 44 μmol of chlorine removed kg−1 week−1) were detected in three out of six sediments sampled from different locations of the lagoon. An uncultured non-Dehalococcoides phylotype of the class Dehalococcoidia closely related to Dehalobium chlorocoercia DF-1, namely phylotype VLD-1, was detected and enriched up to 109 16S rRNA gene copies per gram of sediment where dechlorination activities were higher and 25-4/24-4 and 25-2/24-2/4-4 chlorobiphenyls (CB) accumulated as the main tri-/dichlorinated products. Conversely, a different phylotype closely related to the SF1/m-1 clade, namely VLD-2, also enriched highly where lower dechlorination activity and the accumulation of 25-3 CB as main tri-chlorinated product occurred, albeit in the simultaneous presence of VLD-1. Both phylotypes showed growth yields higher or comparable to known organohalide respirers and neither phylotypes enriched in sediment cultures not exhibiting dechlorination. Conclusions These findings confirm the presence of different PCB-respiring microorganisms in the indigenous microbial communities of Venice Lagoon sediments and relate two non-Dehalococcoides phylotypes of the class Dehalococcoidia to different PCB dechlorination rates and specificities. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0743-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Andrea Nuzzo
- Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131, Bologna, Italy
| | - Andrea Negroni
- Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131, Bologna, Italy
| | - Giulio Zanaroli
- Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131, Bologna, Italy.
| | - Fabio Fava
- Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131, Bologna, Italy
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Kaya D, Imamoglu I, Sanin FD, Payne RB, Sowers KR. Potential risk reduction of Aroclor 1254 by microbial dechlorination in anaerobic Grasse River sediment microcosms. JOURNAL OF HAZARDOUS MATERIALS 2017; 321:879-887. [PMID: 27745958 DOI: 10.1016/j.jhazmat.2016.10.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 09/20/2016] [Accepted: 10/04/2016] [Indexed: 06/06/2023]
Abstract
Aroclor 1254 was the second most produced commercial PCB mixture and is found in soils, sediments and sewage throughout the globe. This commercial PCB mixture is considered particularly toxic because of the relatively high concentrations of congeners with dioxin-like properties. The potential for risk reduction by microbial reductive dechlorination of Aroclor 1254 (A1254) was investigated in sediment microcosms from Grasse River (GR), Massena, NY. The specificity of A1254 dechlorination was doubly- and singly-flanked chlorines in meta positions and to a less extent doubly-flanked para chlorines of 2345-substituted chlorobiphenyl rings. The average dechlorination rate of A1254 was 0.0153 Cl-/biphenyl/day, and dechlorination rates of single congeners ranged between 0.001 and 0.0074 Cl-/biphenyl/day. Potential risk associated with A1254 based on the toxic equivalency factors of the dioxin-like congeners was reduced by 83%. Additional potential risk associated with bioaccumulation in fish was reduced by 35% based on biota-sediment accumulation factor estimates for all detected congeners. Finally, the dechlorination end-products were tri- and tetra-chlorobiphenyls with unflanked chlorines, all of which are susceptible to further degradation by aerobic microorganisms. The combined results indicate that microbial reductive dechlorination has the potential for reducing risk associated with toxicity and bioaccumulation in fish in sites contaminated with A1254.
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Affiliation(s)
- Devrim Kaya
- Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey; Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA; Department of Environmental Engineering, Kocaeli University, Kocaeli, Turkey
| | - Ipek Imamoglu
- Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey
| | - F Dilek Sanin
- Department of Environmental Engineering, Middle East Technical University, Ankara, Turkey
| | - Rayford B Payne
- Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Kevin R Sowers
- Department of Marine Biotechnology, Institute of Marine and Environmental Technology, University of Maryland Baltimore County, Baltimore, MD, USA.
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