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1.
Chemosphere ; 240: 124949, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31568949

RESUMO

Pharmaceutically active compounds are of great concern due to their detection frequency in the environment and the unexpected risks. In this study, the simultaneous removal of mixed pharmaceuticals by microalgae was explored using a typical freshwater diatom Navicula sp. Results showed that Navicula sp. could efficiently remove atenolol, carbamazepine, ibuprofen and naproxen with the efficiencies of >90% after 21 d of exposure. As compared to the removal efficiencies of each pharmaceutical in the individual pharmaceutical treatments, the degradation of sulfamethoxazole, bezafibrate, and naproxen was improved in the mixed treatment, whereas the removal efficiencies of carbamazepine and atenolol decreased. Additionally, the presence of hydrophobic pharmaceuticals (i.e., ibuprofen and naproxen) accelerated the degradation of carbamazepine and sulfamethoxazole and inhibited the removal of atenolol in the mixture with the combination of six pharmaceuticals, while the addition of other pharmaceuticals show no significant effect on the removal of ibuprofen and naproxen. The bioaccumulation of pharmaceuticals in Navicula sp. increased as their log KOW values decreased. Four bezafibrate metabolites were identified and the degradation pathways of bezafibrate in diatom were proposed. It is the first report on the metabolism of BEZ in diatom, and further studies on the environmental risk of the metabolites should be investigated.


Assuntos
Bezafibrato/análise , Biodegradação Ambiental , Diatomáceas/metabolismo , Preparações Farmacêuticas/análise , Preparações Farmacêuticas/metabolismo , Poluentes Químicos da Água/análise , Atenolol/análise , Carbamazepina/análise , Água Doce/química , Ibuprofeno/análise , Inativação Metabólica , Naproxeno/análise , Sulfametoxazol/análise
2.
Chemosphere ; 238: 124560, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31437632

RESUMO

Plastics are the most abundant marine debris globally dispersed in the oceans and its production is rising with documented negative impacts in marine ecosystems. However, the chemical-physical and biological interactions occurring between plastic and planktonic communities of different types of microorganisms are poorly understood. In these respects, it is of paramount importance to understand, on a molecular level on the surface, what happens to plastic fragments when dispersed in the ocean and directly interacting with phytoplankton assemblages. This study presents a computer-aided analysis of electron paramagnetic resonance (EPR) spectra of selected spin probes able to enter the phyoplanktonic cell interface and interact with the plastic surface. Two different marine phytoplankton species were analyzed, such as the diatom Skeletonema marinoi and dinoflagellate Lingulodinium polyedrum, in absence and presence of polyethylene terephthalate (PET) fragments in synthetic seawater (ASPM), in order to in-situ characterize the interactions occurring between the microalgal cells and plastic surfaces. The analysis was performed at increasing incubation times. The cellular growth and adhesion rates of microalgae in batch culture medium and on the plastic fragments were also evaluated. The data agreed with the EPR results, which showed a significant difference in terms of surface properties between the diatom and dinoflagellate species. Low-polar interactions of lipid aggregates with the plastic surface sites were mainly responsible for the cell-plastic adhesion by S. marinoi, which is exponentially growing on the plastic surface over the incubation time.


Assuntos
Diatomáceas/metabolismo , Dinoflagelados/metabolismo , Microalgas/crescimento & desenvolvimento , Fitoplâncton/metabolismo , Plásticos/metabolismo , Polietilenotereftalatos/metabolismo , Ecossistema , Espectroscopia de Ressonância de Spin Eletrônica , Microalgas/metabolismo , Oceanos e Mares , Água do Mar/química , Resíduos/análise
3.
Chemosphere ; 238: 124692, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31545214

RESUMO

Diatomaceous earth or diatom (DE) are naturally available and low cost micro particles with distinct porous structure were used as an adsorbent for the removal of a hazardous dye, Eriochrome Black T (EBT). The surface modification of these DE were performed by sol-gel and hydrothermal methods to obtain a series of adsorbents such as diatom-ceria (DC), diatom-silica xerogel (DX), and diatom-silica xerogel-ceria (DXC). A cauliflower like morphology structure of ceria was observed on DE and DX. The adsorption performance of EBT was conducted by varying various parameters such as pH, adsorbent dosage, initial concentration, contact time and ionic strength. The materials DE, DC, DX and DXC showed the EBT removal efficiencies of 52, 77, 20, and 93%, respectively. The maximum adsorption capacity (qm) of DE, DC, DX and DXC was found to be 13.83, 23.64, 0.2 and 47.02 mgg-1 for the adsorption of EBT, respectively. The selectivity of EBT towards DXC was evaluated by treating a mixture of anionic dyes. The dye removal experiments was performed in presence of inorganic salts, however the presence of these salts did not affect the removal efficiency of DXC. Furthermore, the reusability of DXC was studied by recycling it up to 5 times and even at 5th cycle a removal efficiency of ∼66.8% was found. Thus, these studies demonstrate that the DXC material could be a promising candidate for the removal of EBT via adsorption for real time application in water treatment.


Assuntos
Compostos Azo/análise , Corantes/análise , Terra de Diatomáceas/metabolismo , Diatomáceas/metabolismo , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Porosidade , Reciclagem , Sílica Gel/química
4.
Environ Sci Pollut Res Int ; 26(34): 35107-35120, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31679142

RESUMO

In freshwater ecosystem, phototrophic biofilms play a crucial role through adsorption and sequestration of organic and inorganic pollutants. However, extracellular polymeric substance (EPS) secretion by phototrophic biofilms exposed to metals is poorly documented. This work evaluated the physiological responses of phototrophic biofilms by exposing three microorganisms (cyanobacterium Phormidium autumnale, diatom Nitzschia palea and green alga Uronema confervicolum) to 20 and 200 µg L-1 of Cu or 60 and 600 µg L-1 of Zn, both individually and in combination. Analysis of metal effects on algal biomass and photosynthetic efficiency showed that metals were toxic at higher concentrations for these two parameters together and that all the strains were more sensitive to Cu than to Zn. U. confervicolum was the most impacted in terms of growth, while P. autumnale was the most impacted in terms of photosynthetic efficiency. In consequence to metal exposure at higher concentrations (Cu200, Zn600 and Cu200Zn600), a higher EPS production was measured in diatom and cyanobacterium biofilms, essentially caused by an overproduction of protein-like polymers. On the other hand, the amount of secreted polysaccharides decreased during metal exposure of the diatom and green alga biofilms. Size exclusion chromatography revealed specific EPS molecular fingerprints in P. autumnale and N. palea biofilms that have secreted different protein-like polymers during their development in the presence of Zn600. These proteins were not detected in the presence of Cu200 despite an increase of proteins in the EPS extracts compared to the control. These results highlight interesting divergent responses between the three mono-species biofilms and suggest that increasing protein production in EPS biofilms may be a fingerprint of natural biofilm against metal pollutants in freshwater rivers.


Assuntos
Biofilmes/crescimento & desenvolvimento , Cobre/toxicidade , Zinco/toxicidade , Biofilmes/efeitos dos fármacos , Biomassa , Cobre/análise , Cianobactérias/metabolismo , Diatomáceas/metabolismo , Ecossistema , Matriz Extracelular de Substâncias Poliméricas , Água Doce , Metais/análise , Fotossíntese , Rios , Zinco/análise
5.
Nat Commun ; 10(1): 4552, 2019 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-31591397

RESUMO

Diatoms outcompete other phytoplankton for nitrate, yet little is known about the mechanisms underpinning this ability. Genomes and genome-enabled studies have shown that diatoms possess unique features of nitrogen metabolism however, the implications for nutrient utilization and growth are poorly understood. Using a combination of transcriptomics, proteomics, metabolomics, fluxomics, and flux balance analysis to examine short-term shifts in nitrogen utilization in the model pennate diatom in Phaeodactylum tricornutum, we obtained a systems-level understanding of assimilation and intracellular distribution of nitrogen. Chloroplasts and mitochondria are energetically integrated at the critical intersection of carbon and nitrogen metabolism in diatoms. Pathways involved in this integration are organelle-localized GS-GOGAT cycles, aspartate and alanine systems for amino moiety exchange, and a split-organelle arginine biosynthesis pathway that clarifies the role of the diatom urea cycle. This unique configuration allows diatoms to efficiently adjust to changing nitrogen status, conferring an ecological advantage over other phytoplankton taxa.


Assuntos
Diatomáceas/genética , Diatomáceas/metabolismo , Redes e Vias Metabólicas/genética , Nitrogênio/metabolismo , Carbono/metabolismo , Cloroplastos/genética , Cloroplastos/metabolismo , Evolução Molecular , Perfilação da Expressão Gênica/métodos , Regulação da Expressão Gênica , Metabolômica/métodos , Mitocôndrias/genética , Mitocôndrias/metabolismo , Modelos Biológicos , Nitratos/metabolismo , Proteômica/métodos , Água do Mar/microbiologia , Transdução de Sinais/genética
6.
Nat Commun ; 10(1): 4167, 2019 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-31519883

RESUMO

Diatoms possess an impressive capacity for rapidly inducible thermal dissipation of excess absorbed energy (qE), provided by the xanthophyll diatoxanthin and Lhcx proteins. By knocking out the Lhcx1 and Lhcx2 genes individually in Phaeodactylum tricornutum strain 4 and complementing the knockout lines with different Lhcx proteins, multiple mutants with varying qE capacities are obtained, ranging from zero to high values. We demonstrate that qE is entirely dependent on the concerted action of diatoxanthin and Lhcx proteins, with Lhcx1, Lhcx2 and Lhcx3 having similar functions. Moreover, we establish a clear link between Lhcx1/2/3 mediated inducible thermal energy dissipation and a reduction in the functional absorption cross-section of photosystem II. This regulation of the functional absorption cross-section can be tuned by altered Lhcx protein expression in response to environmental conditions. Our results provide a holistic understanding of the rapidly inducible thermal energy dissipation process and its mechanistic implications in diatoms.


Assuntos
Diatomáceas/metabolismo , Luz , Diatomáceas/fisiologia , Fotossíntese/fisiologia , Complexo de Proteína do Fotossistema II/metabolismo , Complexo de Proteína do Fotossistema II/fisiologia , Xantofilas/metabolismo
7.
Microb Cell Fact ; 18(1): 161, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31547820

RESUMO

BACKGROUND: Numerous studies have shown that stress induction and genetic engineering can effectively increase lipid accumulation, but lead to a decrease of growth in the majority of microalgae. We previously found that elevated CO2 concentration increased lipid productivity as well as growth in Phaeodactylum tricornutum, along with an enhancement of the oxidative pentose phosphate pathway (OPPP) activity. The purpose of this work directed toward the verification of the critical role of glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme in the OPPP, in lipid accumulation in P. tricornutum and its simultaneous rapid growth rate under high-CO2 (0.15%) cultivation. RESULTS: In this study, G6PDH was identified as a target for algal strain improvement, wherein G6PDH gene was successfully overexpressed and antisense knockdown in P. tricornutum, and systematic comparisons of the photosynthesis performance, algal growth, lipid content, fatty acid profiles, NADPH production, G6PDH activity and transcriptional abundance were performed. The results showed that, due to the enhanced G6PDH activity, transcriptional abundance and NAPDH production, overexpression of G6PDH accompanied by high-CO2 cultivation resulted in a much higher of both lipid content and growth in P. tricornutum, while knockdown of G6PDH greatly decreased algal growth as well as lipid accumulation. In addition, the total proportions of saturated and unsaturated fatty acid, especially the polyunsaturated fatty acid eicosapentaenoic acid (EPA; C20:5, n-3), were highly increased in high-CO2 cultivated G6PDH overexpressed strains. CONCLUSIONS: The successful of overexpression and antisense knockdown of G6PDH well demonstrated the positive influence of G6PDH on algal growth and lipid accumulation in P. tricornutum. The improvement of algal growth, lipid content as well as polyunsaturated fatty acids in high-CO2 cultivated G6PDH overexpressed P. tricornutum suggested this G6PDH overexpression-high CO2 cultivation pattern provides an efficient and economical route for algal strain improvement to develop algal-based biodiesel production.


Assuntos
Dióxido de Carbono/metabolismo , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/genética , Ácidos Graxos/metabolismo , Glucosefosfato Desidrogenase/genética , Dióxido de Carbono/análise , Diatomáceas/metabolismo , Engenharia Genética , Glucosefosfato Desidrogenase/metabolismo , Microalgas/genética , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , NADP/metabolismo , Via de Pentose Fosfato , Fotossíntese
8.
BMC Biotechnol ; 19(1): 53, 2019 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-31349823

RESUMO

BACKGROUND: Increasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems. The physiological and biochemical processes of marine phytoplankton in response to ocean acidification have been reported, but have been mainly focused on growth and photosynthetic physiology. To acquire a thorough knowledge of the molecular regulation mechanisms, model species with clear genetic background should be selected for systematic study. Phaeodactylum tricornutum is a pennate diatom with the characteristics of small genome size, short generation cycle, and easy to transform. Furthermore, the genome of P. tricornutum has been completely sequenced. RESULTS AND DISCUSSION: In this study, P. tricornutum was cultured at high and normal CO2 concentrations. Cell composition changes during culture time were investigated. The 13C isotope tracing technique was used to determine fractional labeling enrichments for the main cellular components. The results suggested that when lipid content increased significantly under high CO2 conditions, total protein and soluble sugar contents decreased. The 13C labeling experiment indicated that the C skeleton needed for fatty acid C chain elongation in lipid synthesis under high CO2 conditions is not mainly derived from NaHCO3 (carbon fixed by photosynthesis). CONCLUSION: This study indicated that breakdown of intracellular protein and soluble sugar provide C skeleton for lipid synthesis under high CO2 concentration.


Assuntos
Proteínas de Algas/metabolismo , Dióxido de Carbono/metabolismo , Carbono/metabolismo , Diatomáceas/metabolismo , Lipídeos/biossíntese , Açúcares/metabolismo , Isótopos de Carbono/metabolismo , Diatomáceas/genética , Diatomáceas/fisiologia , Ecossistema , Concentração de Íons de Hidrogênio , Espaço Intracelular/metabolismo , Lipogênese , Oceanos e Mares , Fotossíntese , Água do Mar/química , Solubilidade , Açúcares/química
9.
Bioresour Technol ; 289: 121717, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31279322

RESUMO

To enhance biodiesel production and quality from a bloom-forming diatom Skeletonema costatum, a two-stage model, in which cells were cultured in nutrient replete conditions first and then transferred to nutrient limitation conditions, was explored. Compared to one-stage model, nutrient limitation in the second stage significantly increased lipid content in spite of decreasing growth; consequently, Si-limitation and N-Si-limitation respectively increased lipid productivity by 37.6% and 76.7% for 6 h induction, and 42.8% and 113.7% for 12 induction. Nutrient limitation enhanced the proportions of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) but reduced polyunsaturated fatty acid (PUFA). Therefore, N-Si-limitation reduced iodine value by 33.7% and 45.6% but increased cetane number by 6.4% and 21.6% for 6 and 24 h induction, respectively. These findings indicate that the two-stage model with N-Si-limitation can enhance lipid productivity as well as biodiesel quality from diatoms.


Assuntos
Biocombustíveis , Diatomáceas/metabolismo , Lipídeos/biossíntese , Nitrogênio/farmacologia , Silício/farmacologia , Diatomáceas/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento
10.
Protist ; 170(3): 328-348, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31260945

RESUMO

Diatoms perform an estimated 20% of global photosynthesis, form the base of the marine food web, and sequester carbon into the deep ocean through the biological pump. In some areas of the ocean, diatom growth is limited by the micronutrient cobalamin (vitamin B12), yet the biochemical ramifications of cobalamin limitation are not well understood. In a laboratory setting, we grew the diatom Thalassiosira pseudonana under replete and low cobalamin conditions to elucidate changes in metabolite pools. Using metabolomics, we show that the diatom experienced a metabolic cascade under cobalamin limitation that affected the central methionine cycle, transsulfuration pathway, and composition of osmolyte pools. In T. pseudonana, 5'-methylthioadenosine decreased under low cobalamin conditions, suggesting a disruption in the diatom's polyamine biosynthesis. Furthermore, two acylcarnitines accumulated under low cobalamin, suggesting the limited use of an adenosylcobalamin-dependent enzyme, methylmalonyl CoA mutase. Overall, these changes in metabolite pools yield insight into the metabolic consequences of cobalamin limitation in diatoms and suggest that cobalamin availability may have consequences for microbial interactions that are based on metabolite production by phytoplankton.


Assuntos
Diatomáceas/metabolismo , Metabolômica , Vitamina B 12/metabolismo , Metaboloma
11.
Food Chem ; 297: 124937, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253257

RESUMO

Diatoms are a major group of high omega 3-fatty acid producing algae that play a key role in global climate change and ecosystem function. Phaeodactylum tricornutum is one of only two diatoms whose genomes have been completely sequenced, leading to metabolic engineering of high eicosapentaenoic acid producing strains. Based on its rapid growth, high lipid content, and especially omega-3 long chain unsaturated fatty acids, P. tricornutum exhibits a large commercial potential. However, until now, it is predominately produced as feed for the aquaculture industry, rather than food supplement. This review compares the change of P. tricornutum lipid composition under different treatments, and identifies suitable lipid induction, cultivation and harvesting methods for industry adoption. If produced in a biorefinery setting, P. tricornutum has strong potential for value generation from human health products (omega-3-rich oil and high-value protein) with cost estimates of AU$6.14 per kg dry weight and AU$20.47 for omega-3-rich oil.


Assuntos
Diatomáceas/metabolismo , Ácidos Graxos Ômega-3/metabolismo , Lipídeos/química , Dióxido de Carbono/química , Ácido Eicosapentaenoico/análogos & derivados , Ácido Eicosapentaenoico/metabolismo , Indústria Alimentícia , Concentração de Íons de Hidrogênio
12.
Artigo em Inglês | MEDLINE | ID: mdl-31242666

RESUMO

The rare earth elements are widely used in agricultural and light industry development. They promote the growth of crop seedlings, enhance root development and change the metal properties. Due to the large amount of rare earth minerals mined in China, rare earth elements have been detected in both coastal and estuary areas. They cause pollution and threaten the health of aquatic organisms and human beings. This study investigates the effects of lanthanum on two marine bait algae, and analyzes the changes in the photosynthetic and antioxidant systems of the two algae. The results show that rare earth elements have significant inhibitory effects upon the two algae. The OJIP kinetic curve value decreases with an increasing concentration of La(NO3)3 ·6H2O. The parameters of the fluorescence value were analyzed. The ABS/RC increases and the DI0/RC decreases during the first 24 h after exposure. The effects on the photosynthetic and antioxidant systems at low concentrations (both EC10 and EC20) show that the TR0/ABS increases, and the ET0/RC, ABS/RC, and DI0/RC has a decreasing trend after 30 min. However, after 24 h, normal levels were restored. In addition, the study finds that the TR0/ABS increases after 24 h, leading to an increase in reactive oxygen species. The antioxidant system analysis also confirms the increase in the activities of antioxidant enzymes, such as SOD and GSH. The experiment is expected to support the marine pollution of rare earths and the theoretical data of the impact on marine primary producers.


Assuntos
Chlorella vulgaris/efeitos dos fármacos , Diatomáceas/efeitos dos fármacos , Lantânio/toxicidade , Poluentes Químicos da Água/toxicidade , Chlorella vulgaris/metabolismo , Diatomáceas/metabolismo , Glutationa/metabolismo , Fotossíntese/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo
13.
Plant Cell Physiol ; 60(8): 1811-1828, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31179502

RESUMO

Diatoms are unicellular algae and evolved by secondary endosymbiosis, a process in which a red alga-like eukaryote was engulfed by a heterotrophic eukaryotic cell. This gave rise to plastids of remarkable complex architecture and ultrastructure that require elaborate protein importing, trafficking, signaling and intracellular cross-talk pathways. Studying both plastids and mitochondria and their distinctive physiological pathways in organello may greatly contribute to our understanding of photosynthesis, mitochondrial respiration and diatom evolution. The isolation of such complex organelles, however, is still demanding, and existing protocols are either limited to a few species (for plastids) or have not been reported for diatoms so far (for mitochondria). In this work, we present the first isolation protocol for mitochondria from the model diatom Thalassiosira pseudonana. Apart from that, we extended the protocol so that it is also applicable for the purification of a high-quality plastids fraction, and provide detailed structural and physiological characterizations of the resulting organelles. Isolated mitochondria were structurally intact, showed clear evidence of mitochondrial respiration, but the fractions still contained residual cell fragments. In contrast, plastid isolates were virtually free of cellular contaminants, featured structurally preserved thylakoids performing electron transport, but lost most of their stromal components as concluded from Western blots and mass spectrometry. Liquid chromatography electrospray-ionization mass spectrometry studies on mitochondria and thylakoids, moreover, allowed detailed proteome analyses which resulted in extensive proteome maps for both plastids and mitochondria thus helping us to broaden our understanding of organelle metabolism and functionality in diatoms.


Assuntos
Diatomáceas/metabolismo , Mitocôndrias/metabolismo , Plastídeos/metabolismo , Proteoma/metabolismo , Tilacoides/metabolismo
14.
Bioresour Technol ; 289: 121681, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31247531

RESUMO

This study was conducted to evaluate the potential of the marine diatom Phaeodactylum tricornutum in nutrient removal coupled with biodiesel production using different ratios of mixed municipal wastewater (MW) and seawater (SW) as the growth medium. The results indicated that P. tricornutum exhibited high nutrient removal efficiency with the ratios of MW: SW = 1:1 and MW: SW = 2:1, e.g. 87.7-89.9% for chemical oxygen demand (COD), 82.2-86.7% for total nitrogen (TN), 96.0-97.0% for total phosphorus, and 76.9-84.2% for ammonium (NH3-N). Significantly higher biomass and lipid productivity were obtained with aeration. The highest lipid productivity of P. tricornutum was 54.76 mg/L/day, which was obtained with a two-step cultivation using the ratio of MW: SW = 1:1 by diluting half of the mixture and bubbling with 5% CO2 during the second step. These results suggested that the marine diatom P. tricornutum exhibited great potential for using mixed wastewater for wastewater treatment and biodiesel production.


Assuntos
Diatomáceas/metabolismo , Lipídeos/biossíntese , Água do Mar/química , Águas Residuárias/química , Compostos de Amônio/análise , Biocombustíveis , Análise da Demanda Biológica de Oxigênio , Biomassa , Meios de Cultura , Nitrogênio/análise , Fósforo/análise
15.
Environ Pollut ; 250: 873-882, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31085473

RESUMO

The potential presence of nanoplastics (NP) in aquatic environments represents a growing concern regarding their possible effects on aquatic organisms. The objective of this study was to assess the impact of polystyrene (PS) amino-modified particles (50  nm PSNH2) on the cellular and metabolic responses of the diatom Chaetoceros neogracile cultures at two essential phases of the growth cycle, i.e. exponential (division) and stationary (storage) phases. Both cultures were exposed for 4 days to low (0.05 µg mL-1) and high (5 µg mL-1) concentrations of PS-NH2. Exposure to NP impaired more drastically the major cellular and physiological parameters during exponential phase than during the stationary phase. Only an increase in ROS production was observed at both culture phases following NP exposures. In exponential phase cultures, large decreases in chlorophyll content, esterase activity, cellular growth and photosynthetic efficiency were recorded upon NP exposure, which could have consequences on the diatoms life cycle and higher food-web levels. The observed differential responses to NP exposure according to culture phase could reflect i) the higher concentration of Transparent Exopolymer Particles (TEP) at stationary phase leading to NP aggregation and thus, probably minimizing NP effects, and/or ii) the fact that dividing cells during exponential phase may be intrinsically more sensitive to stress. This work evidenced the importance of algae physiological state for assessing the NP impacts with interactions between NP and TEP being one key factor affecting the fate of NP in algal media and their impact to algal' cells.


Assuntos
Diatomáceas/efeitos dos fármacos , Matriz Extracelular de Substâncias Poliméricas/metabolismo , Nanopartículas/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Poliestirenos/toxicidade , Poluentes Químicos da Água/toxicidade , Clorofila/metabolismo , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/metabolismo , Relação Dose-Resposta a Droga , Cadeia Alimentar , Modelos Teóricos , Tamanho da Partícula
16.
J Agric Food Chem ; 67(24): 6683-6690, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31140797

RESUMO

Fungicides are frequently detected in natural water and have gained increasing attention as a result of their potential toxicity to non-target aquatic organisms. Carbendazim (CAR), a commonly used fungicide, was selected to explore its toxicity and biodegradation in a typical freshwater diatom Navicula sp. Results showed that the growth of Navicula sp. was inhibited by CAR, with a 24 h EC50 value of 2.18 mg L-1. Although the algal growth rate was recovered after 72 h of exposure, the chlorophyll a content remained significantly decreased when the concentration of CAR was above 0.5 mg L-1. Moreover, Navicula sp. had a negative effect on the removal of CAR, and the acute toxicity by CAR was likely due to its rapid accumulation in algal cells. Mass spectrometric data revealed the transformation products of CAR from hydroxylation, methylation, decarboxylation, demethylation, and deamination in algal cultures. These results provide a better understanding of the environmental risks of CAR in water and point to the need for additional studies on the potential adverse biological effects of its intermediates.


Assuntos
Benzimidazóis/metabolismo , Carbamatos/metabolismo , Diatomáceas/metabolismo , Fungicidas Industriais/metabolismo , Poluentes Químicos da Água/metabolismo , Benzimidazóis/química , Benzimidazóis/toxicidade , Carbamatos/química , Carbamatos/toxicidade , Diatomáceas/química , Diatomáceas/efeitos dos fármacos , Diatomáceas/crescimento & desenvolvimento , Água Doce/análise , Fungicidas Industriais/química , Fungicidas Industriais/toxicidade , Espectrometria de Massas , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidade
17.
Environ Pollut ; 251: 363-371, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31091500

RESUMO

Due to the growing concern about the presence of microplastics (MP) in the environment, the number of studies evaluating the toxicity of these small persistent particles on different marine species has increased in recent years. Few studies have addressed their impact on marine phytoplankton, a subject of great concern since they are primary producers of the aquatic food web. The aim of this study is to unravel the cytotoxicity of 2.5 µg mL-1 unlabelled amino-modified polystyrene beads of different sizes (0.5 and 2 µm) on the marine diatom Chaetoceros neogracile. In addition to traditional growth and photosynthesis endpoints, several physiological and biochemical parameters were monitored every 24 h in C. neogracile cells by flow cytometry during their exponential growth (72 h). Dynamic Light Scattering measurements revealed the strong aggregation and the negative charge of the beads assayed in the culture medium, which seemed to minimize particle interaction with cells and potentially associated impacts. Indeed, MP were not attached to the microalgal cell wall, as evidenced by scanning electron micrographs. Cell growth, morphology, photosynthesis, reactive oxygen species levels and membrane potential remained unaltered. However, exposure to MP significantly decreased the cellular esterase activity and the neutral lipid content. Microalgal oil bodies could serve as an energy source for maintaining a healthy cellular status. Thus, MP-exposed cells modulate their energy metabolism to properly acclimate to the stress conditions.


Assuntos
Diatomáceas/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Poliestirenos/toxicidade , Poluentes Químicos da Água/toxicidade , Diatomáceas/metabolismo , Diatomáceas/fisiologia , Microesferas , Tamanho da Partícula , Poliestirenos/química , Poluentes Químicos da Água/química
18.
Environ Monit Assess ; 191(6): 387, 2019 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-31115704

RESUMO

Phytoplankton and epipelon assemblages form the main constituents, and they are producers in aquatic ecosystems, such as streams and rivers. This study was carried out between May 2008 and April 2009 to determine the impacts of polluted water on species variations, compositions, and community metrics in phytoplankton and epipelon at six stations on Ankara Stream. A total of 231 taxa were recorded during the study period, with 131 Bacillariophyta, 3 Charophyta, 41 Chlorophyta, 30 Cyanobacteria, 25 Euglenophyta, and 1 Ochrophyta. Heterogeneity of the stream stations was determined by the use of hierarchical cluster analysis (HCA). Community metrics were compared by using non-parametric tests, while canonical correspondence analysis (CCA) was used for the relationships between environmental variables and species. Variations in water quality and species composition along the stream flow revealed a significant spatial heterogeneity (p < 0.05). However, the upper stations of the stream were represented by unpolluted water quality with low nutrients and conductivity, and the mid- and downstream stations were characterized by high concentrations of ammonia (up to 60 mg L-1) and o-phosphate (up to 25 mg/L), with low concentrations of dissolved oxygen (< 1 mg L-1). The results, clearly supported by indicator taxa, showed that various domestic and industrial discharges affected the increase in pollution and the spatial heterogeneity. The findings obtained in this study will contribute to future improvements in Ankara Stream watershed studies.


Assuntos
Diatomáceas/metabolismo , Monitoramento Ambiental/métodos , Resíduos Industriais/análise , Fitoplâncton/metabolismo , Plantas/metabolismo , Rios/química , Poluição da Água/efeitos adversos , Poluição da Água/análise , Amônia/análise , Biodiversidade , Cianobactérias/classificação , Cianobactérias/metabolismo , Ecossistema , Euglênidos/metabolismo , Oxigênio/análise , Fosfatos/análise , Plantas/classificação , Turquia , Qualidade da Água
19.
Int J Mol Sci ; 20(10)2019 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-31126124

RESUMO

Diatoms are a successful group of marine phytoplankton that often thrives under adverse environmental stress conditions. Members of the Skeletonema genus are ecologically important which may subsist during silicate stress and form a dense bloom following higher silicate concentration. However, our understanding of diatoms' underlying molecular mechanism involved in these intracellular silicate stress-responses are limited. Here an iTRAQ-based proteomic method was coupled with multiple physiological techniques to explore distinct cellular responses associated with oxidative stress in the diatom Skeletonema dohrnii to the silicate limitation. In total, 1768 proteins were detected; 594 proteins were identified as differentially expressed (greater than a two-fold change; p < 0.05). In Si-limited cells, downregulated proteins were mainly related to photosynthesis metabolism, light-harvesting complex, and oxidative phosphorylation, corresponding to inducing oxidative stress, and ROS accumulation. None of these responses were identified in Si-limited cells; in comparing with other literature, Si-stress cells showed that ATP-limited diatoms are unable to rely on photosynthesis, which will break down and reshuffle carbon metabolism to compensate for photosynthetic carbon fixation losses. Our findings have a good correlation with earlier reports and provides a new molecular level insight into the systematic intracellular responses employed by diatoms in response to silicate stress in the marine environment.


Assuntos
Diatomáceas/metabolismo , Silicatos/metabolismo , Carbono/metabolismo , Respiração Celular , Fotossíntese , Proteínas/metabolismo , Proteômica , Espécies Reativas de Oxigênio/metabolismo , Estresse Fisiológico
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