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1.
Aquat Toxicol ; 227: 105588, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32861020

RESUMO

The pollution of polybrominated diphenyl ethers (PBDEs) is becoming a pressing environmental problem in aquatic environments, and its threat to aquatic organism has received much attention. In this study, Phaeodactylum tricornutum was treated with 0.8 and 4 mg L-1 2,2',4,4'-tetrabrominated biphenyl ether (BDE-47), the most toxic PBDEs, for 96 h. BDE-47 inhibited cell growth in a time- and concentration-dependent manner. Observation of cell ultrastructure suggested the damage of the chloroplasts morphology. BDE-47 also decreased the chlorophyll content and the oxygen evolution rate, and altered the performance of photosystems. Transcriptomic analysis revealed differential expression of 62 genes related to photosynthesis in BDE-47 treatments (4 mg L-1) and transcription suppression of 58 genes involved in chlorophyll synthesis, antenna proteins, oxygen evolution, electron transport and downstream carbon fixation, implying potential toxicity targets in cells. Additionally, the levels of reactive oxygen species (ROS) and lipid peroxidation increased under BDE-47 stress and were positively correlated with photosynthesis inhibition. Pretreatment with the ROS scavenger N-acetyl-l-cysteine reduced the extent of inhibition, suggesting that ROS was responsible for these effects. Another experiment with the electron transport chain inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea showed that the generation of ROS was partially blocked, primarily indicating that photosynthetic inhibition induced by BDE-47 contributed to ROS overproduction. Thus, BDE-47 inhibited the photosynthesis by down-regulating the gene expression. This change stimulated ROS production, further leading to chloroplast membrane damage to aggravate this inhibition via a feedback loop. These effects of BDE-47 had adverse outcomes on the entire physiological state and the population growth of the microalgae.


Assuntos
Diatomáceas/efeitos dos fármacos , Éteres Difenil Halogenados/toxicidade , Microalgas/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Poluentes Químicos da Água/toxicidade , Acetilcisteína/farmacologia , Clorofila/metabolismo , Diatomáceas/metabolismo , Diatomáceas/ultraestrutura , Relação Dose-Resposta a Droga , Expressão Gênica/efeitos dos fármacos , Peroxidação de Lipídeos/efeitos dos fármacos , Microalgas/metabolismo , Microalgas/ultraestrutura , Modelos Teóricos , Fotossíntese/genética
2.
Chemosphere ; 260: 127553, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32653748

RESUMO

The impact of ionizing radiation on microorganisms such as microalgae is a topic of increasing importance for understanding the dynamics of aquatic ecosystems in response to environmental radiation, and for the development of efficient approaches for bioremediation of mining and nuclear power plants wastewaters. Currently, nothing is known about the effects of ionizing radiation on the microalgal cell wall, which represents the first line of defence against chemical and physical environmental stresses. Using various microscopy, spectroscopy and biochemical techniques we show that the unicellular alga Chlorella sorokiniana elicits a fast response to ionizing radiation. Within one day after irradiation with doses of 1-5 Gy, the fibrilar layer of the cell wall became thicker, the fraction of uronic acids was higher, and the capacity to remove the main reactive product of water radiolysis increased. In addition, the isolated cell wall fraction showed significant binding capacity for Cu2+, Mn2+, and Cr3+. The irradiation further increased the binding capacity for Cu2+, which appears to be mainly bound to glucosamine moieties within a chitosan-like polymer in the outer rigid layer of the wall. These results imply that the cell wall represents a dynamic structure that is involved in the protective response of microalgae to ionizing radiation. It appears that microalgae may exhibit a significant control of metal mobility in aquatic ecosystems via biosorption by the cell wall matrix.


Assuntos
Chlorella/metabolismo , Metais/metabolismo , Antioxidantes/metabolismo , Biodegradação Ambiental , Biomassa , Parede Celular/metabolismo , Chlorella/efeitos dos fármacos , Ecossistema , Microalgas/metabolismo , Radiação Ionizante , Águas Residuárias
3.
J Biosci Bioeng ; 130(3): 295-305, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32507481

RESUMO

The yield and quality of lipids extracted from microalgal biomass are critical factors in the production of microalgae-based biodiesel. The green microalga Chlorella homosphaera, isolated from Beira Lake, Colombo, Sri Lanka was employed in the present study to identify the effect of chlorophyll removal and cell disruption methods on lipid extraction yield, fatty acid methyl ester (FAME) profile and quality parameters of biodiesel; including cetane number (CN), iodine value (IV), degree of unsaturation (DU) and high heating value (HHV). In the first section of this study, chlorophyll was removed from dry microalgae biomass prior to lipid extraction. Through the analysis of FAME profiles, it was observed that chlorophyll removal yielded biodiesel of enhanced quality, albeit with a lipid loss of 44.2% relative to the control. In the second section of the study, mechanical cell disruption strategies including grinding, autoclaving, water bath heating and microwaving were employed to identify the most effective method to improve lipid recovery from chlorophyll-removed microalgae biomass. Autoclaving (121 °C, 20 min sterilization time, total time 2 h) was the most effective cell disruption technique of the methods tested, in terms of lipid extraction yield (39.80%) and also biodiesel quality. Moreover, it was observed that employing cell disruption subsequent to chlorophyll removal has a significant impact on the FAME profile of microalgae-based biodiesel, and consequently served to increase HHV and CN although IV and DU did not vary significantly.


Assuntos
Biocombustíveis/microbiologia , Biotecnologia , Chlorella/metabolismo , Microalgas/metabolismo , Biomassa , Chlorella/microbiologia , Ácidos Graxos/metabolismo , Microalgas/microbiologia
4.
PLoS One ; 15(6): e0234710, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32555718

RESUMO

Heterotrophic cultures are the most effective approach to overcome low growth rate challenge in the most commercial microalgae. However, the mechanism through which heterotrophic condition regulates algae metabolism are not completely clear. Alternative Splicing (AS) is a common posttranscriptional process by which transcriptome and proteome plasticity increases at different environmental conditions. To identify and characterize of AS events in Auxenochlorella protothecoides microalga grown in autotrophic and heterotrophic, RNA-Seq data were analysed. We found that AS increased with the transition from autotrophic to heterotrophic condition. 705 and 660 differentially expressed (DEG) and spliced (DAS) genes were identified for A.protothecoides was transferred from autotrophic to heterotrophic condition, respectively. Moreover, there was slight coverage between DEG and DAS genes. Furthermore, functional analysis showed that the DAS genes are most frequently related to ion binding and stimulus response. The results also indicated that prevalence of Intron retention is associated with down-regulation of the genes involved in carotenoid biosynthesis. This study provides valuable insights into transcriptional and posttranscriptional plasticity of microalgae during growth mode change.


Assuntos
Processamento Alternativo , Perfilação da Expressão Gênica , Processos Heterotróficos/genética , Microalgas/genética , Microalgas/metabolismo , Carotenoides/metabolismo , Genômica , Microalgas/crescimento & desenvolvimento , Fatores de Tempo
5.
Ecotoxicol Environ Saf ; 201: 110797, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32505760

RESUMO

Microalgae play an important role in arsenic (As) bioaccumulation and biogeochemical cycling in marine ecosystems. Marine microalgal growth and As biotransformation processes depend on environmental factors, including salinity, temperature, and nutrient concentrations, and data in this regard are available in the literature. However, research on the integrated effects of environmental factors on marine diatom species remains scarce and unclear. Herein, salinity and temperature are both considered in combination to investigate their influence on As uptake, biotransformation, and photosynthetic efficiency (PE). Two strains of marine diatom species, Asteroplanus karianus and Skeletonema sp., were cultured in an f/2-based nutrient medium. Microalgae were cultured under various temperatures (5.0, 20, and 35 °C) and salinities (1.0‰, 10‰, 25‰, and 40‰) in association with As and phosphate-enriched (1.0 µmol L-1 of As(V) + 10 µmol L-1 of PO43-) or deficient (20 nmol L-1 of As(V) + 1.0 µmol L-1 of PO43-) conditions. For both species, maximum growth, As accumulation, biotransformation, and PE were recorded at 10 and 14 day of culture. Microalgal growth, As accumulation, biotransformation, and PE were maximum at 20 °C with salinities of 10‰ and 20‰. Cell shape was also observed to be good at optimal at this temperature (20 °C) and range of salinity (10‰ and 20‰). A conceptual model of integrated effects of environmental factors on growth and As accumulation and biotransformation activities by these marine microalgae has been proposed. This study contributed to the elucidation of the relationship between environmental factors and As biotransformation mechanisms, which may further provide significant insight about As remediation processes.


Assuntos
Organismos Aquáticos/efeitos dos fármacos , Arseniatos/toxicidade , Microalgas/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Água do Mar/química , Poluentes Químicos da Água/toxicidade , Organismos Aquáticos/metabolismo , Arseniatos/metabolismo , Transporte Biológico , Biotransformação , Ecossistema , Microalgas/metabolismo , Salinidade , Temperatura , Poluentes Químicos da Água/metabolismo
6.
Chemosphere ; 259: 127418, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32574848

RESUMO

This work evaluated the effect of different initial biomass ratios in a co-culture of an alkaliphilic methanotrophic bacteria consortium (AMB) and the green microalga Scenedesmus obtusiusculus (GM) on the maximum CH4 specific biodegradation rate and global carbon uptake. The highest maximum specific biodegradation rate was 589 ± 0.01 mgCH4 gbiomass-1 d-1 obtained for a proportion of 3:1 AMB-GM (w w-1) and 8% of initial CH4 in the headspace. The methane degradation rate was 1.5 times lower than the value obtained solely by the AMB consortium, and it was associated with pH increases due to the evolved CO2 consumption by the microalga. Increased activity of the AMB consortium along the experiments was due to progressive adaptation. Massive sequencing revealed the presence of methanotrophic/methylotrophic species such as Methylocystis sp., Methylomicrobium sp., Methylophaga sp., and Hyphomicrobium sp. Successful complete methane and carbon dioxide uptake was obtained with the 3:1, 4:1, and 5:1 AMB-GM biomass ratios, while for the rest of the ratios tested, more than 70% of the initial methane was transformed into biomass and inorganic carbon. This study showed that methanotrophic-microalgal co-cultures lead to a promising strategy for greenhouse gases mitigation in one step.


Assuntos
Biodegradação Ambiental , Gases de Efeito Estufa , Metano/metabolismo , Microalgas/fisiologia , Biomassa , Dióxido de Carbono/metabolismo , Técnicas de Cocultura , Methylocystaceae , Microalgas/metabolismo , Scenedesmus/metabolismo
7.
Aquat Toxicol ; 223: 105492, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32361487

RESUMO

In the present study, we tested the hypothesis that high salinity acclimatization can mitigate cadmium (Cd) toxicity in the microalga Dunaliella salina. To this end, microalgal cells were subjected to high salinity (60 g/L) for 12 weeks until the growth rate remained stable between generations and were then exposed to 2.5 mg/L of Cd for 4 days. Acute Cd toxicity impaired cell growth by increasing Cd bioaccumulation and lipid peroxidation, which reduced cellular pigment, total protein, and glutathione content. It also significantly weakened photosynthetic efficiency and total antioxidant capacity. However, acclimatization to high salinity alleviated these negative effects under Cd stress. To understand the potential mechanisms behind this phenomenon, 12 cDNA libraries from control, Cd-exposed (Cd), high salinity-acclimated (Salinity), and high salinity-acclimated with Cd exposure (Salinity + Cd) cells were derived using RNA sequencing. A total of 2019, 1799, 2150 and 1256 differentially expressed genes (DEGs) were identified from sample groups Salinity / Control, Cd / Control, Salinity + Cd / Control, and Salinity + Cd / Cd, respectively. Some of these DEGs were significantly enriched in ribosome, photosynthesis, stress defense, and photosynthesis-antenna proteins. Among these genes, 82 ribosomal genes were up-regulated in Salinity / Control (corrected P = 3.8 × 10-28), while 81 were down-regulated in Cd / Control (corrected P = 1.1 × 10-24). Moreover, high salinity acclimatization up-regulated 8 photosynthesis genes and 18 stress defense genes compared with the control. Additionally, 3 photosynthesis genes, 11 stress defense genes and 11 genes encoding light harvesting proteins were up-regulated by high salinity acclimatization under Cd exposure. Overall, high salinity acclimatization mitigated Cd toxicity, possibly by up-regulating the transcription of photosynthesis, stress defense, and ribosomal genes. These results provide new insights on cross-tolerance in microalgae.


Assuntos
Aclimatação/efeitos dos fármacos , Cádmio/toxicidade , Microalgas/efeitos dos fármacos , Salinidade , Transcriptoma/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Aclimatação/genética , Antioxidantes/metabolismo , Glutationa/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Microalgas/metabolismo , Fotossíntese/fisiologia , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/genética
8.
Aquat Toxicol ; 223: 105495, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32371336

RESUMO

Platinum-based antineoplastic drugs (PBADs) enter the environment via hospital and municipal wastes as reactive and highly toxic molecules. Chlorella vulgaris is a freshwater microalgae and is used as an excellent aquatic model for toxicity assessment. In the present study, the toxicity of PBADs to C. vulgaris was investigated for better understanding of PBADs environmental toxicity. The algae were cultured in Bold´s Basal Medium (BBM) and exposed to different concentrations of PBADs for 48, 72 and 96 h. Then, cell proliferation, the synthesis of photosynthetic pigments, protein content, malondialdehyde (MDA) release and antioxidant potential were determined. IC50 s of cisplatin, carboplatin and oxaliplatin for 96 h of exposure were 106.2, 124.3 and 153.9 mg/L respectively. Cell proliferation, synthesis of chlorophyll a, chlorophyll b and algal protein content significantly decreased in a time and dose-dependent manner. The release of MDA to culture media significantly increased and antioxidant potential decreased. Cisplatin showed more toxic effects on C. vulgaris compared to carboplatin and oxaliplatin indicating its severe toxicity for marine organisms. PBADs induce their toxic effects in algal cells via the interaction with DNA, production of free radicals (such as reactive oxygen species), lipid peroxidation and cell wall damages. Due to these toxic effects of PBADs for various environmental organisms, there must be severe restriction on their release into the environment.


Assuntos
Antineoplásicos/toxicidade , Chlorella vulgaris/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Carboplatina/toxicidade , Chlorella vulgaris/metabolismo , Clorofila/metabolismo , Clorofila A/metabolismo , Cisplatino/toxicidade , Água Doce/química , Peroxidação de Lipídeos/efeitos dos fármacos , Malondialdeído/metabolismo , Microalgas/metabolismo , Oxaliplatina/toxicidade , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo
9.
Aquat Toxicol ; 224: 105498, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32402915

RESUMO

The current study focuses on the ecotoxicity of cobalt oxide nanoparticles (Co3O4 NPs) in the aquatic environment towards freshwater microalgae, Chlorella minutissima. The interaction of Co3O4 NPs with microalgae shows the growth suppressing effect. The 72 h EC 50 (effective concentration of a chemical having 50% of its impact) values of Co3O4 NPs for C. minutissima was 38.16 ± 1.99 mg/L. The decline in chlorophyll a content and increase in reactive oxygen species (ROS) also indicated the compromised physiological state of microalgae. An increased LDH (lactate dehydrogenase) level in treated samples suggests membrane disintegration by Co3O4 NPs. Light microscopy, scanning electron microscopy (SEM) and Energy Dispersive X-Ray-Scanning electron microscopy (EDX-SEM) further confirm cell entrapment and deposition of Co3O4 NPs on the cell surface. Cellular internalization of NPs, as shown by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), also contributes towards the toxicity of NPs. The findings suggest the role of extracellular as well as intracellular nanoparticles (NPs) in exerting a toxic effect on the C. minutissima.


Assuntos
Chlorella/efeitos dos fármacos , Cobalto/toxicidade , Água Doce/química , Nanopartículas Metálicas/toxicidade , Microalgas/efeitos dos fármacos , Óxidos/toxicidade , Poluentes Químicos da Água/toxicidade , Chlorella/metabolismo , Clorofila A/metabolismo , Cobalto/metabolismo , Microalgas/metabolismo , Microscopia Eletrônica de Varredura , Óxidos/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Poluentes Químicos da Água/metabolismo
10.
Chemosphere ; 255: 126914, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387728

RESUMO

Microplastics have aroused widespread concern because of their adverse effects on aquatic organisms. However, the underlying toxicity mechanisms have not been examined in detail. This study investigated the interactions between polystyrene microplastics (PS-MPs) and the model freshwater microalgae Euglena gracilis. The results of transmission electron microscopy showed that the vacuoles of microalgae were induced after 24 h exposure to 1 mg/L PS-MPs (5 µm and 0.1 µm). Furthermore, PS-MPs significantly (p < 0.05) reduced pigment contents. Moreover, superoxide dismutase activities were significantly (p < 0.05) induced in all PS-MPs treated groups. Peroxidase activities were also significantly (p < 0.05) affected by two sizes of PS-MPs (5 µm and 0.1 µm), indicating that oxidative stress was induced after exposure to PS-MPs. At the molecular level, PS-MPs dysregulated the expression of genes involved in cellular processes, genetic information processing, organismal systems, and metabolisms. The KCS gene and the CTR1 gene may be key pathways to induce adverse effects on the E. gracilis after exposure to 5 µm PS-MPs. These findings will help to elucidate the underlying molecular mechanism of microplastics toxicity on freshwater organisms.


Assuntos
Microalgas/efeitos dos fármacos , Poliestirenos/toxicidade , Poluentes Químicos da Água/toxicidade , Organismos Aquáticos/metabolismo , Água Doce , Microalgas/metabolismo , Microplásticos , Estresse Oxidativo/efeitos dos fármacos , Plásticos/toxicidade
11.
Ecotoxicol Environ Saf ; 197: 110609, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32302859

RESUMO

Bisphenol A (BPA) is used throughout the world and it could enter aquatic ecosystems causing harmful effects on humans, animals and plants. The current study relies on the investigation of the toxicity of this emerging pollutant on two freshwater species from different trophic levels: the microalga Chlamydomonas reinhardtii and the clam Corbicula fluminea. After 96 h of exposure to several concentrations of BPA, the growth of C. reinhardtii was affected, being the 96 h-EC50 value for growth 30 mg L-1. The toxicity and bioaccumulation of 30 mg L-1 BPA in microalgae after 24 h of exposure were studied. Several cytotoxicity biomarkers such as vitality, oxidative stress and cytoplasmic membrane potential were altered in exposed cells and microalgae accumulated 0.16 pg BPA cell-1. Regarding C. fluminea, four treatments were established: control without BPA (C); BPA in the food (microalgae pre-exposed for 24 h to 30 mg L-1) (M); BPA in the water (7.5 mg L-1) (W); BPA in both food and water (M + W). After one month of exposure, treated bivalves showed a significantly decrease in the filtration rate and increased lipid peroxidation levels, indicating fitness reduction and oxidative damage. Furthermore, the activities of catalase, glutathione reductase, Se-dependent and total glutathione peroxidase enzymes increased significantly in W and M + W treatments with respect to the control. Clams of the M + W treatment were the most affected, indicating that the little amount of BPA bioaccumulated by microalgae could increase the damage. Emerging contaminants may accumulate in several organisms, such as microalgae, and could have negative impacts on ecosystems.


Assuntos
Compostos Benzidrílicos/toxicidade , Chlamydomonas reinhardtii/efeitos dos fármacos , Corbicula/efeitos dos fármacos , Fenóis/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Compostos Benzidrílicos/farmacocinética , Catalase/metabolismo , Chlamydomonas reinhardtii/metabolismo , Corbicula/metabolismo , Glutationa Peroxidase/metabolismo , Glutationa Redutase/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Microalgas/efeitos dos fármacos , Microalgas/metabolismo , Estresse Oxidativo , Fenóis/farmacocinética
12.
Nat Commun ; 11(1): 1942, 2020 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-32327645

RESUMO

Dimethylsulfoniopropionate (DMSP) is a pivotal compound in marine biogeochemical cycles and a key chemical currency in microbial interactions. Marine bacteria transform DMSP via two competing pathways with considerably different biogeochemical implications: demethylation channels sulfur into the microbial food web, whereas cleavage releases sulfur into the atmosphere. Here, we present single-cell measurements of the expression of these two pathways using engineered fluorescent reporter strains of Ruegeria pomeroyi DSS-3, and find that external DMSP concentration dictates the relative expression of the two pathways. DMSP induces an upregulation of both pathways, but only at high concentrations (>1 µM for demethylation; >35 nM for cleavage), characteristic of microscale hotspots such as the vicinity of phytoplankton cells. Co-incubations between DMSP-producing microalgae and bacteria revealed an increase in cleavage pathway expression close to the microalgae's surface. These results indicate that bacterial utilization of microscale DMSP hotspots is an important determinant of the fate of sulfur in the ocean.


Assuntos
Regulação Bacteriana da Expressão Gênica , Água do Mar/microbiologia , Compostos de Sulfônio/metabolismo , Enxofre/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Redes e Vias Metabólicas/genética , Microalgas/metabolismo , Interações Microbianas , Fitoplâncton/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Rhodobacteraceae/genética , Rhodobacteraceae/metabolismo , Água do Mar/química , Análise de Célula Única , Compostos de Sulfônio/análise , Enxofre/análise , Transcrição Genética
13.
PLoS One ; 15(4): e0231178, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32320403

RESUMO

An assessment of the production, distribution and fate of highly branched isoprenoid (HBI) biomarkers produced by sea ice and pelagic diatoms is necessary to interpret their detection and proportions in the northern Bering and Chukchi Seas. HBIs measured in surface sediments collected from 2012 to 2017 were used to determine the distribution and seasonality of the biomarkers relative to sea ice patterns. A northward gradient of increasing ice algae deposition was observed with localized occurrences of elevated IP25 (sympagic HBI) concentrations from 68-70°N and consistently strong sympagic signatures from 71-72.5°N. A declining sympagic signature was observed from 2012 to 2017 in the northeast Chukchi Sea, coincident with declining sea ice concentrations. HBI fluxes were investigated on the northeast Chukchi shelf with a moored sediment trap deployed from August 2015 to July 2016. Fluxes of sea ice exclusive diatoms (Nitzschia frigida and Melosira arctica) and HBI-producing taxa (Pleurosigma, Haslea and Rhizosolenia spp.) were measured to confirm HBI sources and ice associations. IP25 was detected year-round, increasing in March 2016 (10 ng m-2 d-1) and reaching a maximum in July 2016 (1331 ng m-2 d-1). Snowmelt triggered the release of sea ice algae into the water column in May 2016, while under-ice pelagic production contributed to the diatom export in June and July 2016. Sea ice diatom fluxes were strongly correlated with the IP25 flux, however associations between pelagic diatoms and HBI fluxes were inconclusive. Bioturbation likely facilitates sustained burial of sympagic organic matter on the shelf despite the occurrence of pelagic diatom blooms. These results suggest that sympagic diatoms may sustain the food web through winter on the northeast Chukchi shelf. The reduced relative proportions of sympagic HBIs in the northern Bering Sea are likely driven by sea ice persistence in the region.


Assuntos
Diatomáceas/isolamento & purificação , Camada de Gelo/microbiologia , Microalgas/isolamento & purificação , Análise Espaço-Temporal , Terpenos/análise , Regiões Árticas , Biomarcadores/análise , Diatomáceas/metabolismo , Cadeia Alimentar , Microalgas/metabolismo , Oceanos e Mares , Estações do Ano , Terpenos/metabolismo
14.
Chemosphere ; 252: 126482, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32222520

RESUMO

This study investigated the feasibility of using photoheterotrophic microalga, Desmodesmus armatus SCK, for removal of cesium (Cs+) followed by recovery process using magnetic nanoparticles. The comparison of three microalgae results indicated that D. armatus SCK removed the most Cs+ at both 25 °C and 10 °C. The results also revealed that the use of microalga grown in potassium (K+)-starved condition improves the accumulation of Cs+. Heterotrophic mode with addition of volatile fatty acids (VFAs), especially acetic acids (HAc), also enhanced removal of Cs+ by K+-starved D. armatus SCK; maximum removal efficiency of Cs+ was almost 2-fold higher than that of cells grown without organic carbon source. The Cs+ taken up by this microalga was efficiently harvested using magnetic nanoparticles, polydiallyldimethylammonium (PDDA)-FeO3. Finally, this strain eliminated more than 99% of radioactive 137Cs from solutions of 10, 100, and 1000 Bq mL-1. Therefore, use of K+-starved microalga, D. armatus SCK, with VFAs could be promising means to remove the Cs from the liquid wastes.


Assuntos
Césio/metabolismo , Microalgas/metabolismo , Poluentes Químicos da Água/metabolismo , Césio/análise , Radioisótopos de Césio , Ácidos Graxos Voláteis , Processos Heterotróficos , Fenômenos Magnéticos , Potássio , Poluentes Químicos da Água/análise
15.
Aquat Toxicol ; 222: 105472, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32203794

RESUMO

ß-carotene is an efficient antioxidant and its accumulation is an oxidative response to stressors. Dunaliella salina strain GY-H13 is rich in ß-carotene under environmental stresses, which was selected as material to understand the molecular mechanism underlying ß-carotene biosynthesis. Seven full length cDNA sequences in ß-carotene biosynthesis pathway were cloned, including geranylgeranyl pyrophosphate synthase (GGPS), phytoene synthase (PSY), phytoene desaturase (PDS), 15-cis-zeta-carotene isomerase (ZISO), zeta-carotene desaturase (ZDS), prolycopene isomerase (CRTISO), lycopene beta-cyclase (LCYb). The seven protein sequences from the strain GY-H13 showed the highest similarity with other D. salina strains. Especially, PSY, PDS and LCYb protein sequences shared 100 % identity. Phylogenetic analysis indicated all proteins from GY-H13 firstly clustered with those from other D. salina strains with a bootstrap of 100 %. Multiple alignment indicated several distinct conserved motifs such as aspartate-rich domain (ARD), dinucleotide binding domain (DBD), and carotene binding domain (CBD). These motifs are located near ligand-binding pocket, which may be required for the activity of enzyme. Expression levels of these genes and ß-carotene content were measured over 24-h cycle, showing clear daily dynamics. All genes were dramatically up-regulated in the morning but the highest accumulation of ß-carotene was observed at noon, suggesting a lag-effect between gene transcription and biological response. Furthermore, the accumulation of ß-carotene increased under nitrogen deficiency, Cd exposure and high light and decreased under high salinity in a time-dependent manner. No gene of ß-carotene biosynthesis was up-regulated by high salinity while most genes were activated by the other stresses at the beginning stage of exposure. Growth inhibition and oxidative damage were also observed under high salinity. Overall, transcription activation of ß-carotene biosynthetic genes at the initial stage of stress exposure is a determinant of the increased accumulation of ß-carotene in microalgae, which help their survive under harsh environments. The newly isolated D. salina strain GY-H13 would be a promising microalgae model for investigating the molecular mechanism of stress-induced ß-carotene biosynthesis.


Assuntos
Cádmio/toxicidade , Microalgas/efeitos dos fármacos , Ativação Transcricional/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , beta Caroteno/biossíntese , Sequência de Aminoácidos , Antioxidantes/metabolismo , Liases Intramoleculares/genética , Microalgas/genética , Microalgas/metabolismo , Oxirredutases/genética , Filogenia , Salinidade , beta Caroteno/genética
16.
Ecotoxicol Environ Saf ; 195: 110484, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32200150

RESUMO

Microplastics and nonylphenol (NP) are considered as emerging pollutant and have attracted wide attention, while their combined toxicity on aquatic organisms is barely researched. Therefore, the combined toxicity influence of NP with three types of microplastics containing polyethylene (PE1000, 13 µm and PE, 150 µm), polyamide (PA1000, 13 µm and PA, 150 µm) polystyrene (PS, 150 µm) on microalgae Chlorella pyrenoidosa was analyzed. Both growth inhibition, chlorophyll fluorescence, superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) were determined. We found that single microplastics and NP both inhibited algal growth, thereby causing oxidative stress. The order of inhibition effect in single microplastics experiment was PE1000 > PA1000 > PE ≈ PS > PA. The combined toxicity experiment results indicated that the presence of microplastics had positive effect in terms of alleviating NP toxicity to C. pyrenoidosa, and the microplastics adsorption capacity to NP was the dominant contributing factor for this effect. According to the independent action model, the combined toxicity was antagonistic. Because the negative effect of smaller size microplastics on algal growth was aggravated with prolonged exposure time, the optimum effect of microplastics alleviated NP toxicity was PA1000 at 48 h, while this effect was substituted by PA at 96 h during combined toxicity. Thus, the toxicity of smaller size microplastics has a nonnegligible influence on combined toxicity. This study confirms that microplastics significantly affected the toxicity of organic pollutants on microalgae. Further research on the combined toxicity of smaller size microplastics with pollutants in chronic toxicity is needed.


Assuntos
Chlorella/efeitos dos fármacos , Microplásticos/toxicidade , Fenóis/toxicidade , Poluentes Químicos da Água/toxicidade , Adsorção , Catalase/metabolismo , Chlorella/enzimologia , Chlorella/metabolismo , Interações Medicamentosas , Malondialdeído/metabolismo , Microalgas/efeitos dos fármacos , Microalgas/enzimologia , Microalgas/metabolismo , Microplásticos/química , Estresse Oxidativo , Poliestirenos/toxicidade , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/química
17.
Mar Pollut Bull ; 151: 110844, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32056632

RESUMO

Climate change effects such as ocean acidification (OA) are known to affect the trace metal distribution. This experimental study provides the first data on 209Po uptake rates and 210Po concentration in five microalgae species under different pH scenarios. The experiment was conducted in replicates at three pH conditions 8.2, 8.0, and 7.5, representing the current and future climate change scenario as per IPCC RCP8.5. The 209Po uptake in the phytoplankton was highest in Thalassiosira weissflogi, i.e. 83% of the 209Po tracer was taken up at 8.2 pH whereas the lowest uptake was observed in Dunaliella salina equivalent to 20% at 7.5 pH. Similar behavior was observed in 210Po concentrations in these microalgae, where 210Po ranged between 3.16 ± 0.03 and 11.6 ± 0.04 Bq kg-1 wet weight (ww), with the highest in the Thalassioria weissflogi at 8.2 pH, and the lowest in Dunaliella salina at 7.5 pH. The difference in 209Po uptake and 210Po concentration was statistically significant (p < 0.001) both among species and the pH treatments in the order: Thalassiosira weissflogi > Tetraselmis suecica > Chaetoceros muelleri > Isochrysis galbana > Dunaliella salina and 8.2 > 8.0 > 7.5. A higher concentration of 209Po in seawater was measured at low pH condition in all the experimental tanks. Though the data clearly show the difference in concentration and uptake of polonium at different pH conditions, it is not known if lower pH is affecting the adsorbed or absorbed fraction. A detailed investigation will be required to understand the process as it can have a significant effect on biomagnification and marine food chain transfer under changing climatic scenarios.


Assuntos
Microalgas/metabolismo , Polônio/metabolismo , Poluentes Químicos da Água/metabolismo , Concentração de Íons de Hidrogênio , Fitoplâncton , Polônio/análise , Água do Mar/química , Poluentes Químicos da Água/análise
18.
PLoS One ; 15(2): e0225677, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32084664

RESUMO

Heterotrophic growth mode is among the most promising strategies put forth to overcome the low biomass and secondary metabolites productivity challenge. To shedding light on the underlying molecular mechanisms, transcriptome meta-analysis was integrated with weighted gene co-expression network analysis (WGCNA), connectivity analysis, functional enrichment, and hubs identification. Meta-analysis and Functional enrichment analysis demonstrated that most of the biological processes are up-regulated at heterotrophic growth condition, which leads to change of genetic architectures and phenotypic outcomes. WGNCA analysis of meta-genes also resulted four significant functional modules across logarithmic (LG), transition (TR), and production peak (PR) phases. The expression pattern and connectivity characteristics of the brown module as a non-preserved module vary across LG, TR, and PR phases. Functional analysis identified Carotenoid biosynthesis, Fatty acid metabolism and Methane metabolism as enriched pathways in the non-preserved module. Our integrated approach was applied here, identified some hubs, such as a serine hydroxymethyltransferase (SHMT1), which is the best candidate for development of metabolites accumulating strains in microalgae. Current study provided a new insight into underlying metabolite accumulation mechanisms and opens new avenue for the future applied studies in the microalgae field.


Assuntos
Processos Autotróficos/genética , Processos Heterotróficos/genética , Microalgas/metabolismo , Metabolismo Secundário/fisiologia , Biologia de Sistemas/métodos , Ciclo do Carbono/fisiologia , Carotenoides/metabolismo , Ácidos Graxos/metabolismo , Perfilação da Expressão Gênica , Redes Reguladoras de Genes , Glicina Hidroximetiltransferase/metabolismo , Metano/metabolismo , Microalgas/crescimento & desenvolvimento , Transcriptoma
19.
Chemosphere ; 248: 126094, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32041073

RESUMO

Microalgae have been considered as promising alternative for CO2 fixation and wastewater purification. In our previous work, a hybrid microalgae CO2 fixation concept has been put forward, which initially used carbonate solution absorb CO2, and then provided obtained bicarbonate as nutrition for microalgae growth to avoid the challenge of low CO2 solubility and carbon fixation efficiency in the conventional process. In this work, the proposed hybrid system was further intensified via integrating soybean wastewater nutrition removal with bicarbonate-carbon (NH4HCO3 and KHCO3) conversion. The investigation results indicated that the maximum biomass productivity (0.74 g L-1) and carbon bioconversion efficiency (46.9%) were achieved in low-NH4HCO3 concentration system with pH adjusted to 7. pH adjustment of different bicarbonate systems also enhanced total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) removal efficiency up to 87.5%, 99.5% and 77.6%, respectively. In addition, maximum neutral lipid (14.4 mg L-1·d-1) and polysaccharide (14.5 mg L-1·d-1) productivities could be obtained in the KHCO3 systems, while higher crude protein productivity (48.1 mg L-1·d-1) was yielded in the NH4HCO3 systems.


Assuntos
Bicarbonatos/química , Ciclo do Carbono , Microalgas/metabolismo , Compostos de Potássio/química , Soja/metabolismo , Águas Residuárias/química , Purificação da Água/métodos , Análise da Demanda Biológica de Oxigênio , Biomassa , Carbono/metabolismo , Dióxido de Carbono/metabolismo , Concentração de Íons de Hidrogênio , Microalgas/crescimento & desenvolvimento , Nitrogênio/metabolismo , Fósforo/metabolismo , Reciclagem
20.
Ecotoxicol Environ Saf ; 192: 110261, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32018153

RESUMO

The Chlorella vulgaris has been generally recognized as a promising microalgal model to study stress-related responses due to its ability to withstand against ionizing and non-ionizing radiation. The objective of the present study was to investigate the effect of CaCl2 pre-treatment at different concentrations on the responses of microalga C. vulgaris under gamma radiation toxicity. Changes in growth, physiological parameters and biochemical compositions of the algae pretreated with 0.17 (normal), 5, and 10 mM CaCl2 were analyzed under 300 Gy gamma irradiation and compared to those of gamma-free control. The results showed that parameters including specific growth rate, cell size, chlorophyll and protein contents, ascorbate peroxidase (APX), and superoxide dismutase (SOD) activity, Ferric Reducing Antioxidant Power (FRAP), and the ratios of nucleic acid to protein negatively affected by gamma irradiation. All these parameters, except for the ratios of nucleic acid to protein significantly increased in the algae when pretreated with a CaCl2 content higher than normal concentration. The analysis also showed that parameters including catalase activity, proline, and carotenoid content, the level of lipid peroxidation, and electrolyte leakage (EL) significantly increased under gamma irradiation but not affected significantly under different CaCl2 pre-treatments. Additionally, specific growth rate, chlorophyll a and protein content, APX and SOD activity, FRAP, lipid peroxidation, electrolyte leakage, and the ratios of nucleic acid to protein were the only parameters that significantly affected by the interaction of gamma toxicity and CaCl2 pretreatment. Overall, the results suggested that regardless of the CaCl2 effect, the algal cells responded to gamma radiation more efficiently by increasing proline, carotenoids content, and CAT activity. More important, it was concluded that calcium had an essential role in modifying the detrimental effect of gamma toxicity on the algae mainly by increasing the activity of ascorbate peroxidase and superoxide dismutase and maintaining the reducing antioxidant power (FRAP) of the cells at a high level.


Assuntos
Cloreto de Cálcio/farmacologia , Chlorella vulgaris/efeitos da radiação , Raios gama/efeitos adversos , Tolerância a Radiação/efeitos dos fármacos , Antioxidantes/metabolismo , Ascorbato Peroxidases/metabolismo , Carotenoides/metabolismo , Catalase/metabolismo , Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Chlorella vulgaris/metabolismo , Clorofila/metabolismo , Clorofila A/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Peroxidação de Lipídeos/efeitos da radiação , Microalgas/efeitos dos fármacos , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Microalgas/efeitos da radiação , Prolina/metabolismo , Superóxido Dismutase/metabolismo
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