Organic Xenobiotics Research Articles

Interactive effects of nanoparticles with other contaminants in aquatic organisms: Friend or foe?

The increasing production and use of nanoparticles (NPs) will lead to their release into the aquatic environment, posing a potential threat to the health of aquatic organisms. Both in the water phase and in the sediments NPs could mix and interact with other pollutants, such as organic xenobiotics and heavy metals, leading to possible changes in their bioavailability/bioconcentration/toxicity. However, whether these interactive effects may lead to increased harmful effects in marine organisms is largely unknown. In this work, available data mainly obtained on carbon based NPs and n-TiO2, as examples of widespread NPs, in aquatic organisms are reviewed. Moreover, data are summarized on the interactive effects of n-TiO2 with 2,3,7,8-TCDD and Cd2+, chosen as examples of common and persistent organic and inorganic contaminants, respectively, in the model marine bivalve Mytilus. The results reveal complex and often unexpected interactive responses of NPs with other pollutants, depending on type of contaminant and the endpoint measured, as well as differences in bioaccumulation. The results are discussed in relation with data obtained in freshwater organisms. Overall, information available so far indicate that interactive effects of NPs with other contaminants do not necessarily lead to increased toxicity or harmful effects in aquatic organisms.

Characterization of glutathione S-transferases from Sus scrofa, Cydia pomonella and Triticum aestivum: Their responses to cantharidin

Glutathione S-transferases (GSTs) play a key role in detoxification of xenobiotics in organisms. However, their other functions, especially response to the natural toxin cantharidin produced by beetles in the Meloidae and Oedemeridae families, are less known. We obtained GST cDNAs from three sources: Cydia pomonella (CpGSTd1), Sus scrofa (SsGSTα1), and Triticum aestivum (TaGSTf3). The predicted molecular mass is 24.19, 25.28 and 24.49kDa, respectively. These proteins contain typical N-terminal and C-terminal domains. Recombinant GSTs were heterologously expressed in Escherichia coli as soluble fusion proteins. Their optimal activities are exhibited at pH 7.0–7.5 at 30°C. Activity of CpGSTd1 is strongly inhibited by cantharidin and cantharidic acid, but is only slightly suppressed by the demethylated analog of cantharidin and cantharidic acid. Enzymatic assays revealed that cantharidin has no effect on SsGSTα1 activity, while it significantly stimulates TaGSTf3 activity, with an EC50 value of 0.3852mM. Activities of these proteins are potently inhibited by the known GST competitive inhibitor: S-hexylglutathione (GTX). Our results suggest that these GSTs from different sources share similar structural and biochemical characteristics. Our results also suggest that CpGSTd1 might act as a binding protein with cantharidin and its analogs.

Operation of fill-and-draw reactors fed with bisphenol A as sole carbon and energy source.

While there is ample evidence in the literature that many organic xenobiotics can be biodegraded as sole carbon and energy source by pure batch cultures of selected microorganisms, the same evidence is very limited for continuous or semi-continuous mixed-culture processes simulating biological wastewater treatment plants. This study investigates for the first time whether Bisphenol A (BPA) can be removed and used as sole carbon and energy source by mixed microbial cultures in a semi-continuous process. Four fill and draw bioreactors were inoculated with unacclimated soil and operated at various hydraulic retention times (HRT), in the range of 1.7-4.2 d, using a feed composed solely of BPA (115 mg/l), and mineral salts. At steady-state, the BPA removal in the four reactors varied in the range 7.5-19% and did not show a significant trend with the HRT. The maximum growth rate on BPA was measured in the range 0.29-1.54 d-1.

Magnetically responsive yeast cells: methods of preparation and applications.

Magnetically modified yeast cells represent an interesting type of biocomposite material, applicable in various areas of bioanalysis, biotechnology and environmental technology. In this review, typical examples of magnetic modifications of yeast cells of the genera Saccharomyces, Kluyveromyces, Rhodotorula and Yarrowia are presented, as well as their possible applications as biocatalysts, active part of biosensors and biosorbents for the separation of organic xenobiotics, heavy metal ions and radionuclides.

The Simplest Flowchart Stating the Mechanisms for Organic Xenobiotics-induced Toxicity: Can it Possibly be Accepted as a "Central Dogma" for Toxic Mechanisms?

Xenobiotics causing a variety of toxicity in biological systems could be classified as two types, inorganic and organic chemicals. It is estimated that the organic xenobiotics are responsible for approximately 80~90% of chemical-induced toxicity in human population. In the class for toxicology, we have encountered some difficulties in explaining the mechanisms of toxicity caused especially by organic chemicals. Here, a simple flowchart was introduced for explaining the mechanism of toxicity caused by organic xenobiotics, as the central dogma of molecular biology. This flowchart, referred to as a central dogma, was described based on a view of various aspects as follows: direct-acting chemicals vs. indirect-acting chemicals, cytochrome P450-dependent vs. cytochrome P450-independent biotransformation, reactive intermediates, reactivation, toxicokinetics vs. toxicodynamics, and reversibility vs. irreversibility. Thus, the primary objective of this flowchart is to help better understanding of the organic xenobiotics-induced toxic mechanisms, providing a major pathway for toxicity occurring in biological systems.

Potential and Limits of Biodegradation Processes for the Removal of Organic Xenobiotics from Wastewaters

AbstractIn the removal of organic xenobiotics from wastewaters, biodegradation is an interesting alternative to conventional physical and chemical processes. Biodegradation in biological wastewater treatment plants has the potential advantages of removing the xenobiotics from the environment, transforming them into nontoxic products such as carbon dioxide and new biomass, and being relatively low in cost. Many xenobiotics have been found to be biodegradable as sole carbon and energy source under aerobic conditions, while under anaerobic conditions many chlorinated hydrocarbons can be biodegraded by reductive dechlorination processes. The main limits of biodegradation processes are the limited time for adaptation to the xenobiotics, the very low xenobiotics concentration in the influent, the competition with abiotic removal mechanisms, the limited availability of external substrates for cometabolism, and the intrinsic nonbiodegradability. Existing biological wastewater treatment processes can be modified by using higher values of the solids retention time, bioaugmentation, addition of readily biodegradable substrates to support cometabolism, and the use of anaerobic‐aerobic processes.

Particular Qualities of Surface Water Bodies Pollution with Components of Pharmaceutical Substances

Overview on pharmacological water pollution in various countries is presented. Original data on contamination of water bodies (serving as sources of water supply for Moscow) with medicines components and pharmaceutical substances metabolites are considered. Application of calculation techniques of the “structure-activity” type has been proposed for forecast of by-effects of drugs and pharmacological activity of other organic xenobiotics has been proposed. Some other ways of pharmaceutical contamination reduction have been recommended.

Magnetically-modified natural biogenic iron oxides for organic xenobiotics removal

Biogenic iron oxides have been collected from a water stream and subsequently magnetically modified using water-based magnetic fluid. Both natural and magnetically modified materials have been characterized in detail using wavelength dispersive X-ray fluorescence spectrometry, X-ray powder diffraction, Mossbauer spectroscopy, electron microscopy and BET surface area measurements. The natural material is composed of 2-line ferrihydrite, forming hollow microtubules—sheaths of Leptothrix ochracea, and detrital components. As a result of the ferrofluid modification, maghemite nanoparticles were identified on the surface of the treated material. The active surface area of the bulk, magnetically-modified sample was 148 m2 g−1. The magnetically modified material was tested as inexpensive magnetically responsive adsorbent for the removal of selected organic xenobiotics, namely organic dyes, from aqueous solutions. The observed maximum adsorption capacities ranged between 34.3 and 97.8 mg of dye per 1 g of adsorbent.

Magnetically modified natural biogenic iron oxides for organic xenobiotics removal

Biogenic iron oxides have been collected from a water stream and subsequently magnetically modified using water-based magnetic fluid. Both natural and magnetically modified materials have been characterized in detail using wavelength dispersive X-ray fluorescence spectrometry, X-ray powder diffraction, Mossbauer spectroscopy, electron microscopy and BET surface area measurements. The natural material is composed of 2-line ferrihydrite, forming hollow microtubules—sheaths of Leptothrix ochracea, and detrital components. As a result of the ferrofluid modification, maghemite nanoparticles were identified on the surface of the treated material. The active surface area of the bulk, magnetically-modified sample was 148 m2 g−1. The magnetically modified material was tested as inexpensive magnetically responsive adsorbent for the removal of selected organic xenobiotics, namely organic dyes, from aqueous solutions. The observed maximum adsorption capacities ranged between 34.3 and 97.8 mg of dye per 1 g of adsorbent.

Semi-quantitative actor-based modelling as a tool to assess the drivers of change and physical variables in participatory integrated assessments

Integrated assessments that aim to support sustainable natural resources management require analysing how biophysical systems are impacted by human actions. These analyses are often performed by modelling the physical system, while human actions are prescribed as scenarios and introduced into the physical models by varying the model input. To achieve a more thorough analysis of the human system component in participatory integrated assessments, we developed a semi-quantitative approach for actor-based modelling which focuses on modelling actions of societal actors based on their problem perceptions but also computes the resulting changes of physical system variables. Our approach is intended to support transdisciplinary research and identification of sustainable development options in problem fields with high levels of uncertainty or ignorance, together with the actors that are being modelled. Actor-based modelling is done using an enhanced version of the DANA software. DANA allows modelling the actors in a specific problem field by representing the perception of each actor by directed graphs, and by computing optimal actions from the perspective of each actor. These perception graphs are semi-quantitative causal maps, which can easily be discussed among stakeholders in a participatory process. DANA was extended to support, in addition to actor modelling, the other two steps in actor-based modelling, modelling of actions and modelling of factors. Modelling of actions refers to determining the actions of each actor under certain scenario assumptions, taking into account the diverse problem perceptions of the individual actors in the problem field, the action of the other actors and exogenous changes. Modelling of factors refers to calculating, in a semi-quantitative way, the resulting changes of physical variables (e.g. pollutant emissions), which may serve as input to physical models. We applied actor-based modelling in an integrated assessment of mobile organic xenobiotics in rivers. Our study shows that actor-based modelling allows generating scientifically better founded and more transparent scenarios of the drivers of change in integrated assessments, in particular because they are based on a structured analysis of the actors' problem perceptions.

Identification of organic xenobiotics in urban aquatic environments using time-of-flight mass spectrometry

Qualitative non-target and post-target analysis methods using gas chromatography–time-of-flight mass spectrometry were applied for analysing neutral and acidic organic xenobiotics in urban and suburban water samples. Ten water samples representing wastewater, stormwater and surface water matrices were collected and concentrated using solid phase extraction. Compound identification was performed using a spectral deconvolution program, accurate mass measurements and comparisons with library spectra. The non-target and post-target analyses identified 36 and 18 compounds, respectively. The identification of 10 compounds was afterwards confirmed with standard compounds. Organophosphate esters were the most abundant compound group detected. The combination of non-target and post-target analyses proved a useful tool in the tentative identification of xenobiotics in water samples. Post-target analysis can complement non-target analysis results at low analyte concentrations. Results showed that several organic xenobiotics originate in urban areas and accumulate in the environment. The wastewater sample produced the highest number of identified compounds, but most of these compounds were also found in stormwater samples from the city centre. Nearly all the compounds present in wastewater were additionally detected in the surface water sample taken 3km downstream from the wastewater effluent discharge point. Only a few xenobiotics were otherwise detected in the surface water samples.

Spin labeling ESR investigation of the molecular environment of soil interacting with chemical organic contaminants

This manuscript elucidates the influence of special functional groups of organic xenobiotic chemicals on partly simultaneous molecular binding mechanisms. Organic xenobiotics are released as contaminants into the environment and are partially bound to soil constituents, such as humic substances (HS) and the mineral phase. The interaction of chemical contaminants with HS of soil was investigated using a labeling technique of soil samples with stable nitroxide radicals as model contaminants. These nitroxide radicals only differed in one functionality, a hydroxy or an amino functional group. Electron spin resonance (ESR) analyses of contaminated soil samples showed that the interaction was a multistage process that comprised an initial increase in the concentration of free organic radicals of soil influenced by contaminants with hydroxy or amino functionality, a decrease in the polarity of the molecular environment of soil, and a change in mobility of contaminant molecules. Towards the end of interaction, the concentration of free organic radicals usually decreased. Binding of contaminants to soil constituents via specific functionality was revealed detecting a change in their ESR spectra. Basing on the ESR analyses, a two-way exchange of protons' electron pairs between contaminants and HS was hypothesized to interpret the beginning of interaction.

Temporal and spatial trends of perfluoroalkyl substances in liver of roe deer (Capreolus capreolus)

For more than 50 years perfluoroalkyl substances (PFASs) have found worldwide industrial and household uses. Some PFASs are presumed to be persistent and bioaccumulative. Roe deer (Capreolus capreolus) are thought to be a suitable bioindicator for the accumulation of organic xenobiotics. Due to the ubiquitous nature of PFASs in the environment a retrospective study on temporal trends was carried out. A total of 110 deer liver pools collected from 1989 to 2010 in Germany were analyzed for their levels of PFASs. The highest concentrations were measured for perfluorooctane sulfonate (PFOS) (median 6.3 μg/kg). Perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) were detected with median concentrations of 0.5 μg/kg, 1.2 μg/kg and 0.3 μg/kg, respectively, while concentrations of the other PFASs were below the limit of quantification. PFOS concentrations decreased significantly (rs = −0.741; p = <0.0001) from 9.2 μg/kg in 2000 to 1.8 μg/kg in 2010.

Biodegradation of drotaverine hydrochloride by free and immobilized cells of Rhodococcus rhodochrous IEGM 608

Drotaverine [1-(3,4-diethoxybenzylidene)-6,7-diethoxy-1,2,3,4-tetrahydroisoquinoline] hydrochloride, an antispasmodic drug derived from benzylisoquinoline was evaluated for its biodegradability using a bacterial strain Rhodococcus rhodochrous IEGM 608. The experiments were performed under aerobic conditions with rhodococci cultures able to degrade drotaverine. In the presence of glucose, the removal efficiency of drotaverine by free Rhodoccocus cells pre-grown with isoquinoline was above 80% (200mg/l, initial concentration) after 25days. Rhodococcus immobilization on hydrophobized sawdust enhanced the biodegradation process, with the most marked drotaverine loss being observed during the first 5days of fermentation. High metabolic activity of rhodococcal cells towards drotaverine was confirmed respirometrically. GC-MS analysis of transformation products resulting from drotaverine biodegradation revealed 3,4-diethoxybenzoic acid, 3,4-diethoxybenzaldehyde and 3,4-diethoxybenzoic acid ethyl ester which were detected in the culture medium until drotaverine completely disappeared. Based on these major and other minor metabolites, putative pathways for drotaverine biodegradation were proposed. The obtained data broadened the spectrum of organic xenobiotics oxidized by Rhodoccocus bacteria and proved their potential in decontamination of natural ecosystems from pharma pollutants.

Multi-component trace analysis of organic xenobiotics in surface water containing suspended particular matter by solid phase extraction/gas chromatography–mass spectrometry

Suspended particulate matter (SPM) often disturbs the analysis of surface water by conventional methods, such as liquid–liquid extraction (LLE) or solid phase extraction (SPE), caused by insufficient extraction or by plugging. Water and SPM are therefore often separately analysed, which is associated with high expenditure of time, work and costs. Hence, SPM is partly ignored, if the fraction of sorptively bound analytes is small compared to the total analyte concentration. However, the European Water Framework Directive (WFD, Directive 2000/60/EC) requires explicitly an investigation of the whole water sample including SPM, because many priority and priority hazardous substances can sorb substantially to SPM. Therefore, an SPE disk based method was developed for the determination of 54 priority and priority hazardous pollutants including polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE), organic chlorinated pesticides (OCP) and other pesticides in surface water containing SPM. The developed SPE disk method allows analysis of 1L surface water containing up to 1000mg SPM without prior separation of SPM in about 2h including gas chromatography–mass (GC–MS) spectrometry analysis. The limits of quantification vary in a range of 0.8 to 38ng/L.

Laccase activity in soils: Considerations for the measurement of enzyme activity

Laccases (benzenediol: oxygen oxidoreductases, EC 1.10.3.2) are copper-containing enzymes that catalyze the oxidative conversion of a variety of chemicals, such as mono-, oligo-, and polyphenols and aromatic amines. Laccases have been proposed to participate in the transformation of organic matter and xenobiotics as well as microbial interactions. Several laccase assays have been proposed and used in soils. Here, we show that the optimal pH conditions for the laccase substrates 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS, pH 3–5), 2,6-dimethoxyphenol (4–5.5), L-3,4-dihydroxyphenylalanine (DOPA; 4–6), guaiacol (3.5–5), 4-methylcatechol (3.5–5), and syringaldazine (5.5–7.0) are similar between purified laccases from Trametes versicolor and Pyricularia sp. and soil extracts; the substrate affinities of purified enzymes (KM) and soil extracts were also similar. The laccase assays showed specificity overlap with tyrosinase and ligninolytic peroxidases when hydrogen peroxide is present. The ABTS oxidation assay is able to reliably detect the presence of 13.5pgmL−1 or 0.199×10−12molmL−1 of T. versicolor laccase, which is three times more sensitive than the 2,6-dimethoxyphenol-based assay and more than 40 times more sensitive than any of the other assays. The low molecular mass soil-derived compounds and the isolated fulvic and humic acids influence the laccase assays and should be removed from the soil extracts before measurements of the enzyme activity are performed.

Significance of Xenobiotic Metabolism for Bioaccumulation Kinetics of Organic Chemicals in Gammarus pulex

Bioaccumulation and biotransformation are key toxicokinetic processes that modify toxicity of chemicals and sensitivity of organisms. Bioaccumulation kinetics vary greatly among organisms and chemicals; thus, we investigated the influence of biotransformation kinetics on bioaccumulation in a model aquatic invertebrate using fifteen 14C-labeled organic xenobiotics from diverse chemical classes and physicochemical properties (1,2,3-trichlorobenzene, imidacloprid, 4,6-dinitro-o-cresol, ethylacrylate, malathion, chlorpyrifos, aldicarb, carbofuran, carbaryl, 2,4-dichlorophenol, 2,4,5-trichlorophenol, pentachlorophenol, 4-nitrobenzyl-chloride, 2,4-dichloroaniline, and sea-nine (4,5-dichloro-2-octyl-3-isothiazolone)). We detected and identified metabolites using HPLC with UV and radio-detection as well as high resolution mass spectrometry (LTQ-Orbitrap). Kinetics of uptake, biotransformation, and elimination of parent compounds and metabolites were modeled with a first-order one-compartment model. Bioaccumulation factors were calculated for parent compounds and metabolite enrichment factors for metabolites. Out of 19 detected metabolites, we identified seven by standards or accurate mass measurements and two via pathway analysis and analogies to other compounds. 1,2,3-Trichlorobenzene, imidacloprid, and 4,6-dinitro-o-cresol were not biotransformed. Dietary uptake contributed little to overall uptake. Differentiation between parent and metabolites increased accuracy of bioaccumulation parameters compared to total 14C measurements. Biotransformation dominated toxicokinetics and strongly affected internal concentrations of parent compounds and metabolites. Many metabolites reached higher internal concentrations than their parents, characterized by large metabolite enrichment factors.

Regulation of xenobiotic transporter genes in liver and brain of juvenile thicklip grey mullets (Chelon labrosus) after exposure to Prestige-like fuel oil and to perfluorooctane sulfonate

Xenobiotic transport proteins are involved in cellular defence against accumulation of xenobiotics participating in multixenobiotic resistance (MXR). In order to study the transcriptional regulation of MXR genes in fish exposed to common chemical pollutants we selected the thicklip grey mullet (Chelon labrosus), since mugilids are widespread in highly degraded estuarine environments where they have to survive through development and adulthood. Partial sequences belonging to genes coding for members of 3 different families of ATP binding cassette (ABC) transporter proteins (ABCB1; ABCB11; ABCC2; ABCC3; ABCG2) and a vault protein (major vault protein, MVP) were amplified and sequenced from mullet liver. Their liver and brain transcription levels were examined in juvenile mullets under exposure to perfluorooctane sulfonate (PFOS) and to fresh (F) and weathered (WF) Prestige-like heavy fuel oil for 2 and 16days. In liver, PFOS significantly up-regulated transcription of abcb1, abcb11 and abcg2 while in brain only abcb11 was up-regulated. Both fuel treatments significantly down-regulated abcb11 in liver at day 2 while abcc2 was only down-regulated by WF. mvp was significantly up-regulated by F and down-regulated by WF at day 2 in the liver. At day 16 only a significant up-regulation of abcb1 in the F group was recorded. Brain abcc3 and abcg2 were down-regulated by both fuels at day 2, while abcb1 and abcc2 were only down-regulated by F exposure. After 16days of exposure only abcb11 and abcg2 were regulated. In conclusion, exposure to organic xenobiotics significantly alters transcription levels of genes participating in xenobiotic efflux, especially after short periods of exposure. Efflux transporter gene transcription profiling could thus constitute a promising tool to assess exposure to common pollutants.

Bioaccumulation and catabolism of prometryne in green algae

Investigation on organic xenobiotics bioaccumulation/biodegradation in green algae is of great importance from environmental point of view because widespread distribution of these compounds in agricultural areas has become one of the major problems in aquatic ecosystem. Also, new technology needs to be developed for environmental detection and re-usage of the compounds as bioresources. Prometryne as a herbicide is widely used for killing annual grasses in China and other developing countries. However, overuse of the pesticide results in high risks to contamination to aquatic environments. In this study, we focused on analysis of bioaccumulation and degradation of prometryne in Chlamydomonas reinhardtii, a green alga, along with its adaptive response to prometryne toxicity. C. reinhardtii treated with prometryne at 2.5–12.5μgL−1 for 4d or 7.5μgL−1 for 1–6d accumulated a large quantity of prometryne, with more than 2mgkg−1 fresh weight in cells exposed to 10μgL−1 prometryne. Moreover, it showed a great ability to degrade simultaneously the cell-accumulated prometryne. Such uptake and catabolism of prometryne led to the rapid removal of prometryne from media. Physiological and molecular analysis revealed that toxicology was associated with accumulation of prometryne in the cells. The biological processes of degradation can be interpreted as an internal tolerance mechanism. These results suggest that the green alga is useful in bioremediation of prometryne-contaminated aquatic ecosystems.

Influence of different flow conditions on the occurrence and behavior of potentially hazardous organic xenobiotics in the influent and effluent of a municipal sewage treatment plant in Germany: an effect-directed approach

Flow conditions in the sewer systems are particularly important for the chemical and toxicological characteristics of raw and treated wastewater. Nevertheless, this topic has not been thoroughly investigated to date. In this study, composite wastewater samples were taken daily from the influent and effluent of a municipal sewage treatment plant. Polarity-based fractionation of the samples was carried out through sequential solid phase extractions. Biological testing of single and recombinant fractions was performed using bioluminescence inhibition assay according to DIN EN ISO 11348-2. Selected compounds (pharmaceuticals and polycyclic aromatic hydrocarbons) were also included in the chemical analysis by liquid chromatography coupled with tandem mass spectrometry and gas chromatography coupled with mass spectrometry. By analyzing different flow conditions, this study clarifies how these fractions contribute to the total toxicity of organic substances in wastewater. Additionally, it demonstrates the extent to which the potentially hazardous effects of the fractions can be reduced at the examined sewage treatment plant. Summarizing, medium to highly polar organic compounds were particularly relevant for the total toxicity of organic xenobiotics. For rising wastewater flow under wet weather conditions, we observed a significant decrease in the overall toxicity of the organic pollutants and specifically in the toxic effects of the moderately polar fraction 2. The results provide the starting point for an important risk assessment regarding the occurrence and behavior of potentially toxic xenobiotics by differentiated polarity in municipal wastewater for varying flow conditions.