Dataset Information

Nontarget Analysis Reveals a Bacterial Metabolite of Pyrene Implicated in the Genotoxicity of Contaminated Soil after Bioremediation.

ABSTRACT: Bioremediation is an accepted technology for cleanup of soil contaminated with polycyclic aromatic hydrocarbons (PAHs), but it can increase the genotoxicity of the soil despite removal of the regulated PAHs. Although polar biotransformation products have been implicated as causative genotoxic agents, no specific product has been identified. We pursued a nontarget analytical approach combining effect-directed analysis (EDA) and metabolite profiling to compare extracts of PAH-contaminated soil from a former manufactured-gas plant site before and after treatment in a laboratory-scale aerobic bioreactor. A compound with the composition C15H8O2 and four methylated homologues were shown to accumulate as a result of bioreactor treatment, and the C15H8O2 compound purified from soil extracts was determined to be genotoxic. Its structure was established by nuclear magnetic resonance and mass spectroscopy as a heretofore unidentified ?,?-unsaturated lactone derived from dioxygenation of pyrene at an apical ring, 2H-naphtho[2,1,8-def]chromen-2-one (NCO), which was confirmed by synthesis. The concentration of NCO in the bioreactor was 11 ?g g-1 dry soil, corresponding to 13% of the pyrene removed. It also accumulated in aerobically incubated soil from two additional PAH-contaminated sites and was formed from pyrene by two pyrene-degrading bacterial cultures known to be geographically widespread, underscoring its potential environmental significance.

SUBMITTER: Tian Z

PROVIDER: S-EPMC6309544 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Nontarget Analysis Reveals a Bacterial Metabolite of Pyrene Implicated in the Genotoxicity of Contaminated Soil after Bioremediation.

Tian Zhenyu Z Gold Avram A Nakamura Jun J Zhang Zhenfa Z Vila Joaquim J Singleton David R DR Collins Leonard B LB Aitken Michael D MD

Environmental science & technology 20170530 12

Bioremediation is an accepted technology for cleanup of soil contaminated with polycyclic aromatic hydrocarbons (PAHs), but it can increase the genotoxicity of the soil despite removal of the regulated PAHs. Although polar biotransformation products have been implicated as causative genotoxic agents, no specific product has been identified. We pursued a nontarget analytical approach combining effect-directed analysis (EDA) and metabolite profiling to compare extracts of PAH-contaminated soil fro ...[more]

PMID: 28510420

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Project description:The formation of more polar and toxic polycyclic aromatic hydrocarbon (PAH) transformation products is one of the concerns associated with the bioremediation of PAH-contaminated soils. Soil contaminated with coal tar (prebioremediation) from a former manufactured gas plant (MGP) site was treated in a laboratory scale bioreactor (postbioremediation) and extracted using pressurized liquid extraction. The soil extracts were fractionated, based on polarity, and analyzed for 88 PAHs (unsubstituted, oxygenated, nitrated, and heterocyclic PAHs). The PAH concentrations in the soil tested, postbioremediation, were lower than their regulatory maximum allowable concentrations (MACs), with the exception of the higher molecular weight PAHs (BaA, BkF, BbF, BaP, and IcdP), most of which did not undergo significant biodegradation. The soil extract fractions were tested for genotoxicity using the DT40 chicken lymphocyte bioassay and developmental toxicity using the embryonic zebrafish (Danio rerio) bioassay. A statistically significant increase in genotoxicity was measured in the unfractionated soil extract, as well as in four polar soil extract fractions, postbioremediation (p < 0.05). In addition, a statistically significant increase in developmental toxicity was measured in one polar soil extract fraction, postbioremediation (p < 0.05). A series of morphological abnormalities, including peculiar caudal fin malformations and hyperpigmentation in the tail, were measured in several soil extract fractions in embryonic zebrafish, both pre- and postbioremediation. The increased toxicity measured postbioremediation is not likely due to the 88 PAHs measured in this study (including quinones), because most were not present in the toxic polar fractions and/or because their concentrations did not increase postbioremediation. However, the increased toxicity measured postbioremediation is likely due to hydroxylated and carboxylated transformation products of the 3- and 4-ring PAHs (PHE, 1MPHE, 2MPHE, PRY, BaA, and FLA) that were most degraded.

Project description:Bacterial community dynamics and biodegradation processes were examined in a highly creosote-contaminated soil undergoing a range of laboratory-based bioremediation treatments. The dynamics of the eubacterial community, the number of heterotrophs and polycyclic aromatic hydrocarbon (PAH) degraders, and the total petroleum hydrocarbon (TPH) and PAH concentrations were monitored during the bioremediation process. TPH and PAHs were significantly degraded in all treatments (72 to 79% and 83 to 87%, respectively), and the biodegradation values were higher when nutrients were not added, especially for benzo(a)anthracene and chrysene. The moisture content and aeration were determined to be the key factors associated with PAH bioremediation. Neither biosurfactant addition, bioaugmentation, nor ferric octate addition led to differences in PAH or TPH biodegradation compared to biodegradation with nutrient treatment. All treatments resulted in a high first-order degradation rate during the first 45 days, which was markedly reduced after 90 days. A sharp increase in the size of the heterotrophic and PAH-degrading microbial populations was observed, which coincided with the highest rates of TPH and PAH biodegradation. At the end of the incubation period, PAH degraders were more prevalent in samples to which nutrients had not been added. Denaturing gradient gel electrophoresis analysis and principal-component analysis confirmed that there was a remarkable shift in the composition of the bacterial community due to both the biodegradation process and the addition of nutrients. At early stages of biodegradation, the alpha-Proteobacteria group (genera Sphingomonas and Azospirillum) was the dominant group in all treatments. At later stages, the gamma-Proteobacteria group (genus Xanthomonas), the alpha-Proteobacteria group (genus Sphingomonas), and the Cytophaga-Flexibacter-Bacteroides group (Bacteroidetes) were the dominant groups in the nonnutrient treatment, while the gamma-Proteobacteria group (genus Xathomonas), the beta-Proteobacteria group (genera Alcaligenes and Achromobacter), and the alpha-Proteobacteria group (genus Sphingomonas) were the dominant groups in the nutrient treatment. This study shows that specific bacterial phylotypes are associated both with different phases of PAH degradation and with nutrient addition in a preadapted PAH-contaminated soil. Our findings also suggest that there are complex interactions between bacterial species and medium conditions that influence the biodegradation capacity of the microbial communities involved in bioremediation processes.

Project description:Soil remediation industries continue to seek technologies to speed-up treatment and reduce operating costs. Some processes are energy intensive and, in some cases, transport can be the main source of carbon emissions. Residual fertilizing materials (RFM), such as organic residues, have the potential to be beneficial bioremediation agents. Following a circular economy framework, we investigated the feasibility of sourcing RFMs locally to reduce transport and assess possible bioremediation efficiency gains. RFMs were recruited within 100 km of the treatment site: ramial chipped wood (RCW), horse manure (MANR) and brewer spent grain (BSG). They were added to the land treatment unit's baseline fertilizer treatment (FERT, "F") to measure if they improved the remediation efficiency of an engine oil-contaminated soil (7,500 ± 100 mg kg-1). Results indicate that MANR-F was the only amendment more effective than FERT for petroleum hydrocarbons (PHC) reduction, while emitting the least CO2 overall. RCW-F was equivalent to FERT but retained more moisture. Although BSG contributed the most nitrogen to the soil, BSG-F retained excessive moisture, emitted more volatile organic compounds, contained less soil O2, and was less effective than the baseline treatment. Significantly more of the C16-C22 fraction was removed (63% ± 22%) than all other fractions (C22-C28, C28-C34, C34-C40), which were equally removed. Microbial community-level physiological profiling was conducted with Biolog Ecoplates™, and catabolic diversity differed between treatments (utilization rates of 31 carbon sources). MANR-F has the potential to increase PHC-remediation speed and efficiency compared to inorganic fertilizer alone. Other RFM promote moisture retention and diverse microbial catabolic activity. A variety of RFM are present across the globe and some can offer low-cost amendments to boost remediation efficiency, while reducing treatment time compared to traditional fertilizer-only methods.

Dataset Information

Nontarget Analysis Reveals a Bacterial Metabolite of Pyrene Implicated in the Genotoxicity of Contaminated Soil after Bioremediation.

Publications

Nontarget Analysis Reveals a Bacterial Metabolite of Pyrene Implicated in the Genotoxicity of Contaminated Soil after Bioremediation.

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