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1.
Ecotoxicol Environ Saf ; 221: 112415, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34171691

RESUMO

In order to understand the mechanisms of arsenic (As) accumulation and detoxification in aquatic plants exposed to different As species, a hydroponic experiment was conducted and the three aquatic plants (Hydrilla verticillata, Pistia stratiotes and Eichhornia crassipes) were exposed to different concentrations of As(III), As(V) and dimethylarsinate (DMA) for 10 days. The biomass, the surface As adsorption and total As adsorption of three plants were determined. Furthermore, As speciation in the culture solution and plant body, as well as the arsenate reductase (AR) activities of roots and shoots, were also analyzed. The results showed that the surface As adsorption of plants was far less than total As absorption. Compared to As(V), the plants showed a lower DMA accumulation. P. stratiotes showed the highest accumulation of inorganic arsenic but E. crassipes showed the lowest at the same As treatment. E. crassipes showed a strong ability to accumulate DMA. Results from As speciation analysis in culture solution showed that As(III) was transformed to As(V) in all As(III) treatments, and the oxidation rates followed as the sequence of H. verticillata>P. stratiotes>E. crassipes>no plant. As(III) was the predominant species in both roots (39.4-88.3%) and shoots (39-86%) of As(III)-exposed plants. As(V) and As(III) were the predominant species in roots (37-94%) and shoots (31.1-85.6%) in As(V)-exposed plants, respectively. DMA was the predominant species in both roots (23.46-100%) and shoots (72.6-100%) in DMA-exposed plants. The As(III) contents and AR activities in the roots of P. stratiotes and in the shoots of H. verticillata were significantly increased when exposed to 1 mg·L-1 or 3 mg·L-1 As(V). Therefore, As accumulation mainly occurred via biological uptake rather than physicochemical adsorption, and AR played an important role in As detoxification in aquatic plants. In the case of As(V)-exposed plants, their As tolerance was attributed to the increase of AR activities.


Assuntos
Araceae , Arseniato Redutases/metabolismo , Arsênio , Ácido Cacodílico , Eichhornia , Hydrocharitaceae , Proteínas de Plantas/metabolismo , Poluentes Químicos da Água , Adsorção , Araceae/química , Araceae/metabolismo , Arsênio/química , Arsênio/metabolismo , Ácido Cacodílico/química , Ácido Cacodílico/metabolismo , Eichhornia/química , Eichhornia/metabolismo , Hydrocharitaceae/química , Hydrocharitaceae/metabolismo , Hidroponia , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Brotos de Planta/química , Brotos de Planta/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
2.
Bull Environ Contam Toxicol ; 106(6): 978-982, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34021770

RESUMO

Juvenile common carp were treated with Cd2+ at a sublethal concentration for Cyprinidae (6.4 mg/L). The expression of N-methyl-D-aspartate receptor subunit genes (NR2A, NR2B) and ATP-binding cassette subfamily C member 1 gene (ABCC1) was compared between treated and untreated fish. In addition, cadmium accumulation in the fish tissues was assessed. NR2A was 18.9-fold upregulated by Cd2+ in the eyes (choroid + retina), which accumulated Cd, and was not upregulated in brain, which didn't accumulate Cd. This may have been caused by the blocking of calcium channels by Cd2+, which has a very similar ionic radius to that of Ca2+. ABCC1 was 2.6-fold upregulated in gills and was not upregulated in liver; both tissues accumulated high levels of Cd. This difference may have been caused by the accumulation of predominantly previously inactivated Cd in liver or by some difference in the mechanisms of self-detoxification from Cd2+ in fish gills and liver.


Assuntos
Carpas , Poluentes Químicos da Água , Animais , Cádmio/metabolismo , Cádmio/toxicidade , Carpas/genética , Brânquias/metabolismo , Fígado/metabolismo , Distribuição Tecidual , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/toxicidade
3.
Artigo em Inglês | MEDLINE | ID: mdl-33989122

RESUMO

This study is screened for naphthalene degrading strains from a heavily polluted area with high naphthalene concentration in the rainwater for the effective removal of naphthalene from rainwater. Recently, naphthalene biodegradation has been achieved in water. However, the influences of organics and inorganics in the rainwater on the biodegradation of naphthalene remains unclear. The naphthalene degrading strain Klebsiella sp. (WJ-1) was identified from sewage sludge. The effects of temperature, pH, inoculum size, and rotation speed on the degradation ability of WJ-1 were studied. The results showed that the naphthalene degradation rates of WJ-1 in rainwater were higher than those in aqueous solution at different experimental conditions. The optimal conditions were 30 °C, 10% inoculum size, pH 7.0, and a rotation speed of 150 rpm. The substances in rainwater might be important co-metabolites of naphthalene degradation. Based on intermediate metabolites detected by gas chromatography-mass spectrometer (GC-MS), the naphthalene biodegradation pathway was identified, as being similar to the phthalic acid pathway. These results suggest WJ-1 as a good candidate for the efficient bioremediation of naphthalene from rainwater in heavily polluted areas.


Assuntos
Klebsiella/metabolismo , Naftalenos/metabolismo , Chuva/química , Poluentes Químicos da Água/metabolismo , Biodegradação Ambiental , Concentração de Íons de Hidrogênio , Klebsiella/isolamento & purificação , Redes e Vias Metabólicas , Esgotos/microbiologia , Temperatura
4.
Ecotoxicol Environ Saf ; 219: 112236, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33989919

RESUMO

After application, pesticides remained in the field may contaminate water resources through surface runoff and leaching, posing a threat to aquatic ecosystem. In the current study, the accumulation, translocation, distribution and removal of four triazine pesticides (simazine, atrazine, terbuthylazine and metribuzin) by free floating aquatic plant Eichhornia crassipes (E. crassipes) in water-sediment microcosm were investigated and the removal mechanisms were explored. E. crassipes was exposed to an initial concentration of 50 µg·L-1 and the pesticide levels in water, sediment, roots and shoots of E. crassipes were monitored during 30 days. The results demonstrated that E. crassipes was capable of accumulating triazine pesticides with the bio-concentration factor (BCF) ranging from 0.8 to 18.4. Triazine pesticides were mainly stored in roots, and root accumulation and translocation amount depend on the hydrophobicity of the pesticides. The removal of the pesticides in water were significantly accelerated by the presence of E. crassipes, with the removal efficiency ranging from 66% to 79% after 30 days of treatment. Though phytoaccumulation only constituted 2-18% of the total spiked pesticides in the microcosm, E. crassipes played a vital role in removing simazine, atrazine and metribuzin. However, microbial degradation in sediment was the main pathway for the removal of terbuthylazine in the microcosm. This study demonstrated the potential application of E. crassipes to accelerate removal of contaminants from aquatic environment.


Assuntos
Eichhornia/metabolismo , Praguicidas/metabolismo , Poluentes Químicos da Água/metabolismo , Atrazina/metabolismo , Biodegradação Ambiental , Ecossistema , Praguicidas/análise , Triazinas/metabolismo , Água/metabolismo , Poluentes Químicos da Água/análise
5.
Biosensors (Basel) ; 11(4)2021 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-33920129

RESUMO

Selenium (Se) is an element with many commercial applications as well as an essential micronutrient. Dietary Se has antioxidant properties and it is known to play a role in cancer prevention. However, the general population often suffers from Se deficiency. Green algae, such as Chlorella vulgaris, cultivated in Se-enriched environment may be used as a food supplement to provide adequate levels of Se. We used Raman microspectroscopy (RS) for fast, reliable, and non-destructive measurement of Se concentration in living algal cells. We employed inductively coupled plasma-mass spectrometry as a reference method to RS and we found a substantial correlation between the Raman signal intensity at 252 cm-1 and total Se concentration in the studied cells. We used RS to assess the uptake of Se by living and inactivated algae and demonstrated the necessity of active cellular transport for Se accumulation. Additionally, we observed the intracellular Se being transformed into an insoluble elemental form, which we further supported by the energy-dispersive X-ray spectroscopy imaging.


Assuntos
Chlorella vulgaris/metabolismo , Selênio/metabolismo , Análise Espectral Raman , Bioacumulação , Chlorella vulgaris/química , Selênio/análise , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/metabolismo
6.
Aquat Toxicol ; 235: 105825, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33857871

RESUMO

The impact of desorption kinetics and permeation kinetics on in vitro-based predictions of in vivo hepatic blood clearances is investigated in the present study. Most commonly, possible limitations due to slow desorption of chemicals from albumin or slow permeation of chemicals through cellular membranes are not considered when in vivo clearances are predicted from in vitro biotransformation rate constants. To evaluate whether the most commonly used extrapolation models might thus overlook important kinetic limitations, we compare predictions of in vivo clearance that explicitly consider desorption and permeation kinetics with predictions of in vivo clearance that neglect these aspects. Our results show that strong limitations due to slow permeation kinetics are possible depending on the assumed permeability value. While permeability values estimated with a mechanistic approach are fast enough to avoid significant limitations, other experimentally derived permeability values lead to dramatically decreased in vivo clearance predictions. These latter values lead to unrealistically low in vivo biotransformation estimates. Furthermore, we also evaluated the implications of desorption kinetics using experimentally determined desorption rate constants. These evaluations show that slow desorption kinetics are unlikely to limit in vivo clearance.


Assuntos
Peixes/metabolismo , Fígado/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Biotransformação , Cinética , Taxa de Depuração Metabólica , Modelos Biológicos , Permeabilidade , Poluentes Químicos da Água/toxicidade
7.
Aquat Toxicol ; 235: 105819, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33873058

RESUMO

Despite of physiological and toxicological relevance, the potential of androgens to influence fish lipid metabolism remains poorly explored. Here, brown trout primary hepatocytes were exposed to six concentrations (1 nM to 100 µM) of dihydrotestosterone (DHT) and testosterone (T), to assess changes in the mRNA levels of genes covering diverse lipid metabolic pathways. Acsl1, essential for fatty acid activation, was up-regulated by T and DHT, whereas the lipogenic enzymes FAS and ACC were up-regulated by the highest (100 µM) concentration of T and DHT, respectively. ApoA1, the major component of high-density lipoprotein (HDL), was down-regulated by both androgens. PPARγ, linked to adipogenesis and peroxisomal ß-oxidation, was down-regulated by T and DHT, while Acox1-3I, rate-limiting in peroxisomal ß-oxidation, was down-regulated by T. Fabp1, StAR and LPL were not altered. Our findings suggest that androgens may impact on lipid transport, adipogenesis and fatty acid ß-oxidation and promote lipogenesis in fish liver.


Assuntos
Di-Hidrotestosterona/metabolismo , Testosterona/metabolismo , Truta/fisiologia , Poluentes Químicos da Água/metabolismo , Androgênios/metabolismo , Androgênios/toxicidade , Animais , Di-Hidrotestosterona/toxicidade , Proteínas de Ligação a Ácido Graxo , Ácidos Graxos/metabolismo , Hepatócitos/metabolismo , Hepatócitos/fisiologia , Metabolismo dos Lipídeos , Lipogênese , Fígado/metabolismo , PPAR gama/metabolismo , Testosterona/toxicidade , Truta/metabolismo , Poluentes Químicos da Água/toxicidade
8.
Ecotoxicol Environ Saf ; 217: 112246, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33901781

RESUMO

It is generally expected that biotransformation and excretion of pharmaceuticals occurs similarly in fish and mammals, despite significant physiological differences. Here, we exposed European perch (Perca fluviatilis) to the benzodiazepine drug temazepam at a nominal concentration of 2 µg L-1 for 10 days. We collected samples of blood plasma, muscle, and brain in a time-dependent manner to assess its bioconcentration, biotransformation, and elimination over another 10 days of depuration in clean water. We observed rapid pharmacokinetics of temazepam during both the exposure and depuration periods. The steady state was reached within 24 h of exposure in most individuals, as was complete elimination of temazepam from tissues during depuration. Further, the biologically active metabolite oxazepam was produced via fish biotransformation, and accumulated significantly throughout the exposure period. In contrast to human patients, where a negligible amount of oxazepam is created by temazepam biotransformation, we observed a continuous increase of oxazepam concentrations in all fish tissues throughout exposure. Indeed, oxazepam accumulated more than its parent compound, did not reach a steady state during the exposure period, and was not completely eliminated even after 10 days of depuration, highlighting the importance of considering environmental hazards posed by pharmaceutical metabolites.


Assuntos
Hipnóticos e Sedativos/toxicidade , Percas/fisiologia , Temazepam/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Biotransformação , Hipnóticos e Sedativos/metabolismo , Oxazepam/metabolismo , Percas/metabolismo , Temazepam/metabolismo , Poluentes Químicos da Água/metabolismo
9.
Environ Pollut ; 283: 117096, 2021 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-33866217

RESUMO

Moxidectin is an antiparasitic drug belonging to the class of the macrocyclic lactones, subgroup mylbemicins. It is used worldwide in veterinary practice, but little is known about its potential environmental risks. Thus, we used the zebrafish embryo as a model system to study the potential effects of moxidectin on aquatic non-target organisms. The analyses were performed in two experimental sets: (1) acute toxicity and apical endpoints were characterized, with biomarker assays providing information on the activity levels of catalase (CAT), glutathione S-transferase (GST), lactate dehydrogenase (LDH), and acetylcholinesterase (AChE); and (2) internal concentration and spatial distribution of moxidectin were determined using ultraperformance liquid chromatography quadrupole-time-of-flight mass spectrometry (UPLC-QToF-MS) and matrix-assisted laser desorption/ionization-MS imaging (MALDI-MSi). The acute toxicity to zebrafish embryos (96 hpf) appeared mainly as a decrease in hatching rates (EC50 = 20.75 µg/L). It also altered the enzymatic activity of biomarker enzymes related to xenobiotic processing, anaerobic metabolism, and oxidative stress (GST, LDH, and CAT, respectively) and strongly accumulated in the embryos, as internal concentrations were 4 orders of magnitude higher than those detected in exposure solutions. MALDI-MSi revealed accumulations of the drug mainly in the head and eyes of the embryos (72 and 96 hpf). Thus, our results show that exposure to moxidectin decreases hatching success by 96 h and alters biochemical parameters in the early life stages of zebrafish while accumulating in the head and eye regions of the animals, demonstrating the need to prioritize this compound for environmental studies.


Assuntos
Poluentes Químicos da Água , Peixe-Zebra , Animais , Bioacumulação , Biomarcadores/metabolismo , Embrião não Mamífero/metabolismo , Macrolídeos , Estresse Oxidativo , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/metabolismo
10.
Ecotoxicol Environ Saf ; 217: 112199, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33864982

RESUMO

Environmental aging of ubiquitous microplastics (MP) occurs through the action of biotic and abiotic factors, and aged MP exhibit different physicochemical properties and environmental behavior from virgin MP. This study aimed to investigate the aged micro-sized polystyrene (mPS) and polyvinyl chloride (mPVC), and the heavy metals copper (Cu) and cadmium (Cd), and examine the effects of their combined toxicities on microalga Chlorella vulgaris. Results showed that the presence of MP inhibited cell growth as compared with the control, the inhibition rate (I) decreased as concentrations of MP rose and aged MP exhibited stronger inhibition of cells than did virgin MP. The largest I was achieved in each culture with the MP concentration of 0.01 g/L, in which aged mPS with the maximal of 36.84% (Iaged mPS) followed by aged mPVC (Iaged mPVC = 30.03%), virgin mPS (Ivirgin mPS = 29.10%) and virgin mPVC (Ivirgin mPVC = 16.72%). Addition of the heavy metals Cu2+ and Cd2+ significantly inhibited cell growth, and toxicity increased with concentrations in a range of 0.5-2.0 mg/L; the maximum I values were 19.50% (ICu) and 85.14% (ICd), respectively. The combined toxicity of aged MP + Cu or aged MP + Cd was less than that of individual heavy metals. In particular, as compared with the maximal ICd of 85.14% achieved by single Cd2+, the toxicity of Cd2+ was greatly reduced when combined with aged mPS and mPVC, with the I value decreased to 27.55% (Iaged mPS) and 32.51% (Iaged mPVC), respectively. Both single and combined treatments caused cell damage to the microalga, accompanied by increased superoxide dismutase (SOD) and intracellular malonaldehyde (MDA) content.


Assuntos
Chlorella vulgaris/metabolismo , Metais Pesados/toxicidade , Microplásticos/toxicidade , Poluentes Químicos da Água/toxicidade , Disponibilidade Biológica , Cádmio/toxicidade , Chlorella vulgaris/efeitos dos fármacos , Cobre/toxicidade , Malondialdeído/farmacologia , Metais Pesados/metabolismo , Microalgas/metabolismo , Microplásticos/metabolismo , Plásticos , Poliestirenos/toxicidade , Cloreto de Polivinila , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/metabolismo
11.
Molecules ; 26(8)2021 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-33923373

RESUMO

Silver nanoparticles (AgNPs) are favoured antibacterial agents in nano-enabled products and can be released into water resources where they potentially elicit adverse effects. Herein, interactions of 10 and 40 nm AgNPs (10-AgNPs and 40-AgNPs) with aquatic higher plant Salvinia minima at 600 µg/L in moderately hard water (MHW), MHW of raised calcium (Ca2+), and MHW containing natural organic matter (NOM) were examined. The exposure media variants altered the AgNPs' surface properties, causing size-dependent agglomeration. The bio-accessibility in the ascending order was: NOM < MHW < Ca2+, was higher in plants exposed to 10-AgNPs, and across all exposures, accumulation was higher in roots compared to fronds. The AgNPs reduced plant growth and the production of chlorophyll pigments a and b; the toxic effects were influenced by exposure media chemistry, and the smaller 10-AgNPs were commonly the most toxic relative to 40-AgNPs. The toxicity pattern was linked to the averagely higher dissolution of 10-AgNPs compared to the larger counterparts. The scanning electron microscopy and X-ray fluorescence analytical techniques were found limited in examining the interaction of the plants with AgNPs at the low exposure concentration used in this study, thus challenging their applicability considering the even lower predicted environmental concentrations AgNPs.


Assuntos
Nanopartículas Metálicas/efeitos adversos , Prata/efeitos adversos , Traqueófitas/metabolismo , Poluentes Químicos da Água/metabolismo , Bioacumulação , Traqueófitas/efeitos dos fármacos
12.
Int J Mol Sci ; 22(6)2021 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-33805783

RESUMO

In anaerobic bioreactors, the electrons produced during the oxidation of organic matter can potentially be used for the biological reduction of pharmaceuticals in wastewaters. Common electron transfer limitations benefit from the acceleration of reactions through utilization of redox mediators (RM). This work explores the potential of carbon nanomaterials (CNM) as RM on the anaerobic removal of ciprofloxacin (CIP). Pristine and tailored carbon nanotubes (CNT) were first tested for chemical reduction of CIP, and pristine CNT was found as the best material, so it was further utilized in biological anaerobic assays with anaerobic granular sludge (GS). In addition, magnetic CNT were prepared and also tested in biological assays, as they are easier to be recovered and reused. In biological tests with CNM, approximately 99% CIP removal was achieved, and the reaction rates increased ≈1.5-fold relatively to the control without CNM. In these experiments, CIP adsorption onto GS and CNM was above 90%. Despite, after applying three successive cycles of CIP addition, the catalytic properties of magnetic CNT were maintained while adsorption decreased to 29 ± 3.2%, as the result of CNM overload by CIP. The results suggest the combined occurrence of different mechanisms for CIP removal: adsorption on GS and/or CNM, and biological reduction or oxidation, which can be accelerated by the presence of CNM. After biological treatment with CNM, toxicity towards Vibrio fischeri was evaluated, resulting in ≈ 46% detoxification of CIP solution, showing the advantages of combining biological treatment with CNM for CIP removal.


Assuntos
Ciprofloxacina/metabolismo , Elétrons , Nanopartículas de Magnetita/química , Nanotubos de Carbono/química , Esgotos/microbiologia , Poluentes Químicos da Água/metabolismo , Adsorção , Aliivibrio fischeri/efeitos dos fármacos , Aliivibrio fischeri/crescimento & desenvolvimento , Anaerobiose/fisiologia , Biodegradação Ambiental , Reatores Biológicos , Ciprofloxacina/isolamento & purificação , Humanos , Nanopartículas de Magnetita/ultraestrutura , Methanobacterium/metabolismo , Methanobrevibacter/metabolismo , Methanosarcinales/metabolismo , Methanospirillum/metabolismo , Testes de Sensibilidade Microbiana , Nanotubos de Carbono/ultraestrutura , Oxirredução , Poluentes Químicos da Água/isolamento & purificação
13.
Aquat Toxicol ; 234: 105811, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33812312

RESUMO

Toxicokinetic (TK) models refer to the process of contaminant bioaccumulation as a balance between rate of uptake from different sources (e.g., water or food), and rate of elimination via different processes such as excretion, growth and/or biotransformation. Biotransformation can considerably modify the fate of chemicals in an organism, especially their bioavailability, residence time, and toxicity. Invertebrate models generally neglect this process as they assume a low metabolic activity. However, some species such as Gammarus sp. amphipods are able to metabolize a vast range of organic compounds. Some recent TK models include biotransformation, but they prove limited for estimating related parameters by giving negative values and/or large uncertainties for biotransformation rate(s). Here we propose a generic TK model accounting for biotransformation using a Bayesian framework for simultaneously estimating the parameters. We illustrated the added value of our method by fitting this generic TK model to 22 published datasets of several benthic invertebrate species exposed to different chemicals. All parameters are estimated simultaneously for all datasets and showed narrow estimates. Furthermore, the median model predictions and their 95% credibility intervals showed that the model confidently fitted the data. In most cases the uncertainties around biotransformation rate(s) were reduced in comparison to the original studies. From a methodology standpoint, this paper reflects that Bayesian inference has real added value for simultaneously estimating all TK parameters for parent chemicals and their metabolite(s) based on all available data, while accounting for different types of data and the correlation between parameters. Bayesian inference was able to overcome the limits of previous methods, since no parameters were fixed and no irrelevant negative values were obtained. Moreover, the 95% credibility intervals around model predictions, which are core uncertainties for Environmental Risk Assessment, were easily acquired.


Assuntos
Invertebrados/metabolismo , Compostos Orgânicos/metabolismo , Poluentes Químicos da Água/metabolismo , Anfípodes/metabolismo , Animais , Teorema de Bayes , Biotransformação , Modelos Teóricos
14.
Aquat Toxicol ; 234: 105806, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33819675

RESUMO

We studied the temperature dependence of accumulation and elimination of two polychlorinated biphenyls (PCBs; PCB-70 and PCB-126) and a commercial mixture of congeners of polybrominated diphenyl ethers (PBDEs; DE-71™)) in Northern leopard frog (Lithobates pipiens) tadpoles. We reared tadpoles at 18, 23, or 27 °C for 5.3 or up to 13.6 weeks (longer at cooler temperature where development is slower) on diets containing the toxicants, each at several different toxicant concentrations, and compared tissue concentrations as a function of food concentration and rearing temperature. Following > 1 month of accumulation, tissue concentrations of all three toxicants in exposed tadpoles were linearly related to dietary concentrations as expected for first order kinetics, with no significant effect of rearing temperature.We also raised free-swimming L. pipiens tadpoles for 14 days on foods containing either toxicant at 18 or 27 °C during an accumulation phase, and then during depuration (declining toxicant) phase of 14 days we provided food without toxicants and measured the decline of toxicants in tadpole tissue. All the congeners were eliminated faster at warmer rearing temperature, as expected. Using Arrhenius' equation, we calculated that the apparent activation energy for elimination of both PCB congeners by tadpoles was 1.21 eV (95% confidence interval 0.6-1.8 eV). We discuss how this value was within the range of estimates for metabolic reactions generally (range 0.2 - 1.2 eV), which might include metabolic pathways for biotransformation and elimination of PCBs. Furthermore, we discuss how the lack of an effect of rearing temperature on tadpole near-steady-state tissue residue levels suggests that faster elimination at the warmer temperature was balanced by faster uptake, which is plausible considering the similar temperature sensitivities (i.e., activation energies) of all these processes. Although interactions between toxicants and temperature can be complex and likely toxicant-dependent, it is plausible that patterns observed in tadpoles might apply to other aquatic organisms. Published data on depuration in 11 fish species eliminating 8 other organic toxicants indicated that they also had similar apparent activation energy for elimination (0.82 ± 0.12 eV; 95% confidence interval 0.56 - 1.08 eV), even though none of those studied toxicants were PCBs or PBDEs. Additional research on toxicant-temperature interactions can help improve our ability to predict toxicant bioaccumulation in warming climate scenarios.


Assuntos
Éteres Difenil Halogenados/metabolismo , Bifenilos Policlorados/metabolismo , Rana pipiens/crescimento & desenvolvimento , Animais , Éteres Difenil Halogenados/química , Éteres Difenil Halogenados/toxicidade , Larva/química , Larva/efeitos dos fármacos , Larva/metabolismo , Bifenilos Policlorados/química , Bifenilos Policlorados/toxicidade , Rana pipiens/metabolismo , Temperatura , Toxicocinética , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/toxicidade
15.
Appl Environ Microbiol ; 87(11)2021 05 11.
Artigo em Inglês | MEDLINE | ID: covidwho-1225696

RESUMO

The widely prescribed pharmaceutical metformin and its main metabolite, guanylurea, are currently two of the most common contaminants in surface and wastewater. Guanylurea often accumulates and is poorly, if at all, biodegraded in wastewater treatment plants. This study describes Pseudomonas mendocina strain GU, isolated from a municipal wastewater treatment plant, using guanylurea as its sole nitrogen source. The genome was sequenced with 36-fold coverage and mined to identify guanylurea degradation genes. The gene encoding the enzyme initiating guanylurea metabolism was expressed, and the enzyme was purified and characterized. Guanylurea hydrolase, a newly described enzyme, was shown to transform guanylurea to one equivalent (each) of ammonia and guanidine. Guanidine also supports growth as a sole nitrogen source. Cell yields from growth on limiting concentrations of guanylurea revealed that metabolism releases all four nitrogen atoms. Genes encoding complete metabolic transformation were identified bioinformatically, defining the pathway as follows: guanylurea to guanidine to carboxyguanidine to allophanate to ammonia and carbon dioxide. The first enzyme, guanylurea hydrolase, is a member of the isochorismatase-like hydrolase protein family, which includes biuret hydrolase and triuret hydrolase. Although homologs, the three enzymes show distinct substrate specificities. Pairwise sequence comparisons and the use of sequence similarity networks allowed fine structure discrimination between the three homologous enzymes and provided insights into the evolutionary origins of guanylurea hydrolase.IMPORTANCE Metformin is a pharmaceutical most prescribed for type 2 diabetes and is now being examined for potential benefits to COVID-19 patients. People taking the drug pass it largely unchanged, and it subsequently enters wastewater treatment plants. Metformin has been known to be metabolized to guanylurea. The levels of guanylurea often exceed that of metformin, leading to the former being considered a "dead-end" metabolite. Metformin and guanylurea are water pollutants of emerging concern, as they persist to reach nontarget aquatic life and humans, the latter if it remains in treated water. The present study has identified a Pseudomonas mendocina strain that completely degrades guanylurea. The genome was sequenced, and the genes involved in guanylurea metabolism were identified in three widely separated genomic regions. This knowledge advances the idea that guanylurea is not a dead-end product and will allow for bioinformatic identification of the relevant genes in wastewater treatment plant microbiomes and other environments subjected to metagenomic sequencing.


Assuntos
Proteínas de Bactérias/metabolismo , Guanidina/análogos & derivados , Hidrolases/metabolismo , Redes e Vias Metabólicas , Metformina/metabolismo , Ureia/análogos & derivados , Poluentes Químicos da Água/metabolismo , Amônia/metabolismo , Proteínas de Bactérias/genética , Biodegradação Ambiental , Biomineralização , Genoma Bacteriano/genética , Guanidina/metabolismo , Hidrolases/genética , Família Multigênica , Pseudomonas mendocina/genética , Pseudomonas mendocina/isolamento & purificação , Pseudomonas mendocina/metabolismo , Especificidade por Substrato , Ureia/metabolismo , Águas Residuárias/microbiologia
16.
Ecotoxicol Environ Saf ; 214: 112064, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33691241

RESUMO

Hydrophyte decomposition caused large amounts of dissolved organic matter (DOM) to enter aquatic environment that influence the migration and transformation of heavy metals (HMs). Six hydrophytes with five dry weight gradients (DWG) were used for the decomposition experiments. The results showed that protein-like materials occupy relatively high content in the hydrophyte-derived DOM. The binding properties of DOM-Cu(II) have been explored by using two-dimensional correlation spectroscopy (2D-COS) in conjunction with synchronous fluorescence spectroscopy (SFS) and log-transformed SFS. The weak signals of binding site can be amplified by the log-transformed 2D-COS analysis. Herein, more binding sites can be identified by the log-transformed 2D-COS analysis. The results reveal that tryptophan-like materials show a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively low DWG and sediment DOM, and fulvic-like substances indicate a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively high DWG. Meanwhile, the results of binding parameters indicate that the log K is the range of 3.61-4.25, 4.33-4.74, 4.59-4.97, 3.91-4.41, and 4.14-4.78 for D1-D5, respectively, suggesting that hydrophyte decomposition can change the binding affinity between DOM components and Cu(II). The complexes of fluorescent components with Cu(II) showed a high log K value at long wavelength (e.g. humic-like substances), and a relatively low fluorescent ligand proportion (f%) at shorter wavelength in the hydrophyte-derived DOM. However, the log K is the range of 3.08-4.31, 4.09-4.45, 3.93-4.35, 4.39-4.75, and 3.95-4.36 for C1-C5, separately. Protein-like substances with Cu(II) showed a relatively high log K value with the exception of C4. The log-transformed 2D-COS can be an analytical tool to understand the binding heterogeneity of DOM with HMs. The study can provide a guide for managing and controlling the effects of hydrophyte decomposition.


Assuntos
Cobre/metabolismo , Poluentes Químicos da Água/metabolismo , Corantes , Cobre/química , Substâncias Húmicas/análise , Metais Pesados/química , Espectrometria de Fluorescência/métodos
17.
Ecotoxicol Environ Saf ; 214: 112082, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33721579

RESUMO

This study investigates the effects of polycyclic aromatic hydrocarbons (PAHs) on two potentially toxic Pseudo-nitzschia hasleana and P. mannii, isolated from a PAH contaminated marine environment. Both species, maintained in non-axenic cultures, have been exposed during 144 h to increasing concentrations of a 15 PAHs mixture. Analysis of the domoic acid, showed very low concentrations. Dose-response curves for growth and photosynthesis inhibition were determined. Both species have maintained their growth until the end of incubation even at the highest concentration tested (120 µg l-1), Nevertheless, P mannii showed faster growth and seemed to be more tolerant than P. hasleana. To reduce PAH toxicity, both species have enhanced their biovolume, with a higher increase for P. mannii relative to P hasleana. Both species were also capable of bio-concentrating PAHs and were able to degrade them probably in synergy with their associated bacteria. The highest biodegradation was observed for P. mannii, which could harbored more efficient hydrocarbon-degrading bacteria. This study provides the first evidence that PAHs can control the growth and physiology of potentially toxic diatoms. Future studies should investigate the bacterial community associated with Pseudo-nitzschia species, as responses to pollutants or to other environmental stressors could be strongly influence by associated bacteria.


Assuntos
Diatomáceas/fisiologia , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Poluentes Químicos da Água/toxicidade , Adaptação Fisiológica , Bactérias , Biodegradação Ambiental , Diatomáceas/metabolismo , Ácido Caínico/análogos & derivados , Fotossíntese , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Poluentes Químicos da Água/metabolismo
18.
Chemosphere ; 276: 129977, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33684862

RESUMO

Todays, with the industrialization of human societies, pollution of aquatic ecosystems with plastics derivatives are a serious concern, affecting the life of their organisms. The present study was conducted to investigate the size effects of micro-plastic, polystyrene on some physiological lesions of the goldfish, Carassius auratus. Fish were exposed to two sizes (0.25 and 8 µm) polystyrene at different environmentally relevant concentrations. The exposure trial was done in two steps. First, fish exposed to a stable concentration of 300 mg/L polystyrene for 168 h. Gill, intestine, and liver tissues were sampled every 24 h to investigate the accumulation of polystyrene. Then, fish were exposed in three replicates to 0 (control), 0.05, 0.5, and 5 mg/L polystyrene in two sizes of 0.25 and 8 µm for 28 days. After the exposure period, gill, liver, and intestine tissues were sampled for histological study, also, serum samples were collected for biochemical assays. Fluorescent microscope observations confirmed the accumulation of polystyrene in tissue samples with time. In addition, histological lesions were found in the liver, intestine, and gill of the exposed fish. The severity of lesions showed a size and dose-dependent pattern. Polystyrene induced the antioxidant system of exposed fish through elevating the levels of SOD and CAT activity and significant difference in expression of antioxidant related genes (CAT, SOD and HSP70). In conclusion, the results of the present study confirmed the toxic effects of microplastic, polystyrene on goldfish.


Assuntos
Carpa Dourada , Poluentes Químicos da Água , Animais , Ecossistema , Expressão Gênica , Carpa Dourada/genética , Sistema Imunitário , Fígado/metabolismo , Microplásticos , Estresse Oxidativo , Plásticos/metabolismo , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/toxicidade
19.
Appl Environ Microbiol ; 87(11)2021 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-33741630

RESUMO

The widely prescribed pharmaceutical metformin and its main metabolite, guanylurea, are currently two of the most common contaminants in surface and wastewater. Guanylurea often accumulates and is poorly, if at all, biodegraded in wastewater treatment plants. This study describes Pseudomonas mendocina strain GU, isolated from a municipal wastewater treatment plant, using guanylurea as its sole nitrogen source. The genome was sequenced with 36-fold coverage and mined to identify guanylurea degradation genes. The gene encoding the enzyme initiating guanylurea metabolism was expressed, and the enzyme was purified and characterized. Guanylurea hydrolase, a newly described enzyme, was shown to transform guanylurea to one equivalent (each) of ammonia and guanidine. Guanidine also supports growth as a sole nitrogen source. Cell yields from growth on limiting concentrations of guanylurea revealed that metabolism releases all four nitrogen atoms. Genes encoding complete metabolic transformation were identified bioinformatically, defining the pathway as follows: guanylurea to guanidine to carboxyguanidine to allophanate to ammonia and carbon dioxide. The first enzyme, guanylurea hydrolase, is a member of the isochorismatase-like hydrolase protein family, which includes biuret hydrolase and triuret hydrolase. Although homologs, the three enzymes show distinct substrate specificities. Pairwise sequence comparisons and the use of sequence similarity networks allowed fine structure discrimination between the three homologous enzymes and provided insights into the evolutionary origins of guanylurea hydrolase.IMPORTANCE Metformin is a pharmaceutical most prescribed for type 2 diabetes and is now being examined for potential benefits to COVID-19 patients. People taking the drug pass it largely unchanged, and it subsequently enters wastewater treatment plants. Metformin has been known to be metabolized to guanylurea. The levels of guanylurea often exceed that of metformin, leading to the former being considered a "dead-end" metabolite. Metformin and guanylurea are water pollutants of emerging concern, as they persist to reach nontarget aquatic life and humans, the latter if it remains in treated water. The present study has identified a Pseudomonas mendocina strain that completely degrades guanylurea. The genome was sequenced, and the genes involved in guanylurea metabolism were identified in three widely separated genomic regions. This knowledge advances the idea that guanylurea is not a dead-end product and will allow for bioinformatic identification of the relevant genes in wastewater treatment plant microbiomes and other environments subjected to metagenomic sequencing.


Assuntos
Proteínas de Bactérias/metabolismo , Guanidina/análogos & derivados , Hidrolases/metabolismo , Redes e Vias Metabólicas , Metformina/metabolismo , Ureia/análogos & derivados , Poluentes Químicos da Água/metabolismo , Amônia/metabolismo , Proteínas de Bactérias/genética , Biodegradação Ambiental , Biomineralização , Genoma Bacteriano/genética , Guanidina/metabolismo , Hidrolases/genética , Família Multigênica , Pseudomonas mendocina/genética , Pseudomonas mendocina/isolamento & purificação , Pseudomonas mendocina/metabolismo , Especificidade por Substrato , Ureia/metabolismo , Águas Residuárias/microbiologia
20.
Ecotoxicol Environ Saf ; 214: 112124, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33711578

RESUMO

Aniline, a synthetic compound widely used in industrial and pesticide production, is a potential environmental pollutant. The removal of aniline is extremely important to minimize threats to human health and the surrounding environment. The objectives of this study were to investigate the removal efficiency and physiological response of Salix. babylonica cuttings to aniline pollution. Photosynthesis, chlorophyll fluorescence, spectral reflectance and the concentration of aniline in leaves, stems and roots were analysed. The experiment showed that S. babylonica has a strong removal effect on aniline wastewater. Cuttings from S. babylonica stems and roots played an important role in accumulating aniline. However, this increase in aniline concentration was dose dependent and was not always linear. With increasing aniline concentration in S. babylonica was increasingly stressed, with negative impacts on photosynthesis, chlorophyll fluorescence and spectral reflectance index in S. babylonica leaves. These results indicate that non-stomatal limitations are the main reason for the reduction in Pn in S. babylonica leaves due to chlorophyll structure destruction under aniline stress. In addition, aniline concentrations result in an unbalanced distribution of excitation energy between the two light systems, thereby hindering photosynthetic electron transfer and restricting the efficient operation of photosynthesis. Salix babylonica can endure moderate concentrations of aniline and has potential for the phyto-management of aniline-polluted wastewater, although further studies are needed using polluted wastewater.


Assuntos
Compostos de Anilina/metabolismo , Salix/metabolismo , Poluentes Químicos da Água/metabolismo , Biodegradação Ambiental , Clorofila/metabolismo , Fotossíntese , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Caules de Planta/metabolismo , Águas Residuárias/análise
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