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Evaluating the effects of bioremediation on genotoxicity of polycyclic aromatic hydrocarbon-contaminated soil using genetically engineered, higher eukaryotic cell lines.

ABSTRACT: Bioremediation is one of the commonly applied remediation strategies at sites contaminated with polycyclic aromatic hydrocarbons (PAHs). However, remediation goals are typically based on removal of the target contaminants rather than on broader measures related to health risks. We investigated changes in the toxicity and genotoxicity of PAH-contaminated soil from a former manufactured-gas plant site before and after two simulated bioremediation processes: a sequencing batch bioreactor system and a continuous-flow column system. Toxicity and genotoxicity of the residues from solvent extracts of the soil were determined by the chicken DT40 B-lymphocyte isogenic cell line and its DNA-repair-deficient mutants. Although both bioremediation processes significantly removed PAHs from the contaminated soil (bioreactor 69% removal, column 84% removal), bioreactor treatment resulted in an increase in toxicity and genotoxicity over the course of a treatment cycle, whereas long-term column treatment resulted in a decrease in toxicity and genotoxicity. However, when screening with a battery of DT40 mutants for genotoxicity profiling, we found that column treatment induced DNA damage types that were not observed in untreated soil. Toxicity and genotoxicity bioassays can supplement chemical analysis-based risk assessment for contaminated soil when evaluating the efficacy of bioremediation.

SUBMITTER: Hu J

PROVIDER: S-EPMC3348858 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Evaluating the effects of bioremediation on genotoxicity of polycyclic aromatic hydrocarbon-contaminated soil using genetically engineered, higher eukaryotic cell lines.

Hu Jing J Nakamura Jun J Richardson Stephen D SD Aitken Michael D MD

Environmental science & technology 20120405 8

Bioremediation is one of the commonly applied remediation strategies at sites contaminated with polycyclic aromatic hydrocarbons (PAHs). However, remediation goals are typically based on removal of the target contaminants rather than on broader measures related to health risks. We investigated changes in the toxicity and genotoxicity of PAH-contaminated soil from a former manufactured-gas plant site before and after two simulated bioremediation processes: a sequencing batch bioreactor system and ...[more]

PMID: 22443351

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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:BackgroundThe PIG-A gene mutation assay is a valuable tool for measuring in vivo gene mutations in blood cells. The human PIG-A assay, used as a potential genotoxicity biomarker, is minimally invasive, sensitive, and cost-efficient; however, the relationship between carcinogen exposure and PIG-A mutations is not well understood.MethodsWe investigated the genotoxic effect of red blood cells using PIG-A assay and lymphocyte cytokinesis-block micronucleus test in barbecue restaurant workers (N = 70) exposed to polycyclic aromatic hydrocarbons (PAHs) and self-identified healthy control subjects (N = 56). Urinary PAH metabolites were measured to evaluate internal exposure levels.ResultsMultivariate Poisson regression showed that the PAH-exposed workers exhibited significantly higher PIG-A mutant frequency (MF) (8.04 ± 6.81 × 10- 6) than did the controls (5.56 ± 5.26 × 10- 6) (RR = 0.707, 95% CI: 0.615-0.812, P < 0.001). These results indicate that PAH exposure is a risk factor for elevated PIG-A MF. The frequencies of micronuclei (MN) and nuclear buds (NBUD) in the PAH-exposed workers (MN: 3.06 ± 2.07 ‰, NBUD: 1.38 ± 1.02 ‰) were also significantly higher than in the controls (MN: 1.46 ± 0.64 ‰, P < 0.001; NBUD: 0.70 ± 0.60 ‰, P < 0.001). Additionally, PIG-A MFs showed better associations with several urinary hydroxylated PAH metabolites (P2-OH-Flu = 0.032, r2-OH-Flu = 0. 268; P2-OH-Phe = 0.022, r2-OH-Phe = 0.286; P3-OH-Phe = 0.0312, r3-OH-Phe = 0.270; P4-OH-Phe = 0.018, r4-OH-Phe = 0.296), while the increase in MN, NPB, and NBUD frequencies was not associated with any OH-PAH metabolites; and high-PAH-exposed workers showed the highest PIG-A MFs. Furthermore, there was a significant association between PIG-A MF and PAH exposure levels (Chi-square test for trend, P = 0.006).ConclusionsOur results indicate that an increase in PIG-A MF in barbecue workers could reflect the response to PAH exposure, providing evidence of its potential as a genotoxicity biomarker in human risk assessment.

Dataset Information

Evaluating the effects of bioremediation on genotoxicity of polycyclic aromatic hydrocarbon-contaminated soil using genetically engineered, higher eukaryotic cell lines.

Publications

Evaluating the effects of bioremediation on genotoxicity of polycyclic aromatic hydrocarbon-contaminated soil using genetically engineered, higher eukaryotic cell lines.

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