Browsing by Author "Soares, Eduardo V."
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- ABCC Subfamily Vacuolar Transporters are Involved in Pb (Lead) Detoxification in Saccharomyces cerevisiaePublication . Sousa, Cátia A.; Hanselaer, Simon; Soares, Eduardo V.The present work has as objective to contribute for the elucidation of the mechanism associated with Pb detoxification, using the yeast Saccharomyces cerevisiae as a model organism. The deletion of GTT1 or GTT2 genes, coding for functional glutathione transferases (GST) enzymes in S. cerevisiae, caused an increased susceptibility to high Pb concentrations (500-1000 μmol L(-1)). These results suggest that the formation of glutathione-Pb conjugate (GS-Pb), dependent of GSTs, is important in Pb detoxification. The involvement of ATP-binding cassette (ABC) vacuolar transporters, belonging to class C subfamily (ABCC) in vacuolar compartmentalization of Pb, was evaluated. For this purpose, mutant strains disrupted in YCF1, VMR1, YBT1 or BPT 1 genes were used. All mutants tested, without vacuolar ABCC transporters, presented an increased sensitivity to 500-1000 μmol L(-1) Pb comparative to wild-type strain. Taken together, the obtained results suggest that Pb detoxification, by vacuolar compartmentalization, can occur as a result of the concerted action of GSTs and vacuolar ABCC transporters. Pb is conjugated with glutathione, catalysed by glutathione transferases and followed to the transport of GS-Pb conjugate to the vacuole by ABCC transporters.
- Alleviation of Fe-induced chlorosis of soybean plants grown in calcareous soil by a freeze-dried iron fertilizer containing siderophores produced by Rhizobium radiobacterPublication . Arcas, Alejandra; Sadeghi, S. Maryam; Lucena, Juan J.; Vindeirinho, João M.; Soares, Eduardo V.; Soares, Helena M. V. M.; López-Rayo, SandraThe concerns about the unsustainability of traditional synthetic Fe chelates lead to the search for new environmentally friendly alternatives, such as siderophores-based fertilizers. In this work, the focus was on the evaluation of a bio-based Fe-chelate fertilizer obtained from the culture of the siderophore-producer bacterium Rhizobium radiobacter. The suitability of a freeze-dried fertilizer formulated from a R. radiobacter culture labeled with 57Fe to alleviate Fe chlorosis in soybean plants cultivated in calcareous soil was analyzed and the new potential Fe fertilizer was evaluated in comparison to the traditional synthetic chelate o,oEDDHA/57Fe3+. This natural chelate was able to maintain chlorophyll content stable during all the pot trials and presented greater Fe concentration in the remaining soil fractions serving as an Fe pool for a long time whereas o,oEDDHA/57Fe3+ could supply Fe quickly. The new bio-based Fe siderophore fertilizer, derived from R. radiobacter culture, could be a green substitute to conventional synthetic chelates to address Fe chlorosis in calcareous soil conditions.
- Alternative chelating agents: Evaluation of the ready biodegradability and complexation propertiesPublication . Martins, J.G.; Neto, Isabel F. F.; Pinto, Isabel S.S.; Soares, Eduardo V.; Barros, Maria T.; Soares, Helena MariaThe ready biodegradability of four chelating agents, N,N -(S,S)-bis[1-carboxy-2-(imidazol-4-yl)ethyl]ethylenediamine (BCIEE), N - ethylenedi-L-cysteine (EC), N,N -bis (4-imidazolymethyl)ethylenediamine (EMI) and 2,6-pyridine dicarboxylic acid (PDA), was tested according to the OECD guideline for testing of chemicals. PDA proved to be a readily biodegradable substance. However, none of the other three compounds were degraded during the 28 days of the test. Chemical simulations were performed for the four compounds in order to understand their ability to complex with some metal ions (Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb, Zn) and discuss possible applications of these chelating agents. Two different conditions were simulated: (i) in the presence of the chelating agent and one metal ion, and (ii) in the simultaneous presence of the chelating agent and all metal ions with an excess of Ca. For those compounds that were revealed not to be readily biodegradable (BCIEE, EC and EMI), applications were evaluated where this property was not fundamental or even not required. Chemical simulations pointed out that possible applications for these chelating agents are: food fortification, food process, fertilizers, biocides, soil remediation and treatment of metal poisoning. Additionally, chemical simulations also predicted that PDA is an efficient chelating agent for Ca incrustations removal, detergents and for pulp metal ions removal process.
- Assessment of cellular reduced glutathione content in Pseudokirchneriella subcapitata using monochlorobimanePublication . Machado, Manuela D.; Soares, Eduardo V.The green alga Pseudokirchneriella subcapitata has been extensively used for the assessment of adverse impacts of pollutants. Glutathione is involved in antioxidant defence and drug detoxification. Intracellular reduced glutathione (GSH) concentration can be used as an indicator of the health of cells. This work describes a simple and fast fluorescent cell-based assay for the evaluation of intracellular GSH in the alga P. subcapitata, using monochlorobimane (mBCl). Metabolically active algal cells incubated with 50 μmol L−1 mBCl form fluorescent bimane–glutathione (B-SG) adducts that can be measured fluorometrically. The distribution of GSH (B-SG adducts) in whole cells can be observed by epifluorescence microscopy, in the form of blue fluorescent spots. Depletion of cellular GSH with iodoacetamide, inhibition of glutathione S-transferase with ethacrynic acid or heat-induced death of the cells inhibited the formation of fluorescent adducts in the presence of mBCl. The fluorometric assay, using the 96-well microplate format, was able to detect GSH depletion in algal cells. This cell-based assay can be used to evaluate decreases in GSH content due to exposure to toxicants. This assay is amenable to automation and may be useful in high-throughput toxicity screening using the alga P. subcapitata.
- Bioremediation of industrial effluents containing heavy metals using brewing cells of Saccharomyces cerevisiae as a green technology: a reviewPublication . Soares, Eduardo V.; Soares, Helena M. V. M.The release of heavy metals into the environment, mainly as a consequence of anthropogenic activities, constitutes a worldwide environmental pollution problem. Unlike organic pollutants, heavy metals are not degraded and remain indefinitely in the ecosystem, which poses a different kind of challenge for remediation. It seems that the “best treatment technologies” available may not be completely effective for metal removal or can be expensive; therefore, new methodologies have been proposed for the detoxification of metal-bearing wastewaters. The present work reviews and discusses the advantages of using brewing yeast cells of Saccharomyces cerevisiae in the detoxification of effluents containing heavy metals. The current knowledge of the mechanisms of metal removal by yeast biomass is presented. The use of live or dead biomass and the influence of biomass inactivation on the metal accumulation characteristics are outlined. The role of chemical speciation for predicting and optimising the efficiency of metal removal is highlighted. The problem of biomass separation, after treatment of the effluents, and the use of flocculent characteristics, as an alternative process of cell–liquid separation, are also discussed. The use of yeast cells in the treatment of real effluents to bridge the gap between fundamental and applied studies is presented and updated. The convenient management of the contaminated biomass and the advantages of the selective recovery of heavy metals in the development of a closed cycle without residues (green technology) are critically reviewed.
- Chronic exposure of the freshwater alga Pseudokirchneriella subcapitata to five oxide nanoparticles: Hazard assessment and cytotoxicity mechanismsPublication . Sousa, Cátia A.; Soares, Helena M.V.M.; Soares, Eduardo V.The increasing use of nanoparticles (NPs) unavoidably enhances their unintended introduction into the aquatic systems, raising concerns about their nanosafety. This work aims to assess the toxicity of five oxide NPs (Al2O3, Mn3O4, In2O3, SiO2 and SnO2) using the freshwater alga Pseudokirchneriella subcapitata as a primary producer of ecological relevance. These NPs, in OECD medium, were poorly soluble and unstable (displayed low zeta potential values and presented the tendency to agglomerate). Using the algal growth inhibition assay and taking into account the respective 72 h-EC50 values, it was possible to categorize the NPs as: toxic (Al2O3 and SnO2); harmful (Mn3O4 and SiO2) and non-toxic/non-classified (In2O3). The toxic effects were mainly due to the NPs, except for SnO2 which toxicity can mainly be attributed to the Sn ions leached from the NPs. A mechanistic study was undertaken using different physiological endpoints (cell membrane integrity, metabolic activity, photosynthetic efficiency and intracellular ROS accumulation). It was observed that Al2O3, Mn3O4 and SiO2 induced an algistatic effect (growth inhibition without loss of membrane integrity) most likely as a consequence of the cumulative effect of adverse outcomes: i) reduction of the photosynthetic efficiency of the photosystem II (ФPSII); ii) intracellular ROS accumulation and iii) loss of metabolic activity. SnO2 NPs also provoked an algistatic effect probably as a consequence of the reduction of ФPSII since no modification of intracellular ROS levels and metabolic activity were observed. Altogether, the results here presented allowed to categorize the toxicity of the five NPs and shed light on the mechanisms behind NPs toxicity in the green alga P. subcapitata.
- Cleanup of industrial effluents containing heavy metals: a new opportunity of valorising the biomass produced by brewing industryPublication . Soares, Eduardo V.; Soares, Helena MariaHeavy metal pollution is a matter of concern in industrialised countries. Contrary to organic pollutants, heavy metals are not metabolically degraded. This fact has two main consequences: its bioremediation requires another strategy and heavy metals can be indefinitely recycled. Yeast cells of Saccharomyces cerevisiae are produced at high amounts as a by-product of brewing industry constituting a cheap raw material. In the present work, the possibility of valorising this type of biomass in the bioremediation of real industrial effluents containing heavy metals is reviewed. Given the autoaggregation capacity (flocculation) of brewing yeast cells, a fast and off-cost yeast separation is achieved after the treatment of metal-laden effluent, which reduces the costs associated with the process. This is a critical issue when we are looking for an effective, eco-friendly, and low-cost technology. The possibility of the bioremediation of industrial effluents linked with the selective recovery of metals, in a strategy of simultaneous minimisation of environmental hazard of industrial wastes with financial benefits from reselling or recycling the metals, is discussed.
- Comparison of five bacterial strains producing siderophores with ability to chelate iron under alkaline conditionsPublication . Ferreira, Carlos M. H.; Vilas-Boas, Ângela; Sousa, Cátia A.; Soares, Helena M. V. M.; Soares, Eduardo V.Iron deficiency is one of the main causes of chlorosis in plants, which leads to losses in field crops quality and yield. The use of synthetic chelates to prevent or correct iron-deficiency is not satisfactory mainly due to their poor biodegradability. The present work aimed to search suitable microorganisms to produce alternative, environment-friendly iron-chelating agents (siderophores). For this purpose, the performance of five bacteria (Azotobacter vinelandii, Bacillus megaterium, Bacillus subtilis, Pantoea allii and Rhizobium radiobacter) was evaluated, regarding siderophore production kinetics, level of siderophore production (determined by chrome azurol S, CAS method), type of siderophore produced (using Arnow and Csaky's tests) and iron-chelating capacity at pH 9.0. All bacteria were in stationary phase at 24 h, except A. vinelandii (at 72 h) and produced the maximum siderophore amount (80-140 µmol L-1) between 24 and 48 h, with the exception of A. vinelandii (at 72 h). The analysis of culture filtrates revealed the presence of catechol-type siderophores for B. subtilis and R. radiobacter and hydroxamate-type siderophores for B. megaterium and P. allii. In the case of A. vinelandii, both siderophore-types (catechol and hydroxamates) were detected. The highest iron-chelating capacity, at pH 9.0, was obtained by B. megaterium followed by B. subtilis and A. vinelandii. Therefore, these three bacteria strains are the most promising bacteria for siderophore production and chlorosis correction under alkaline conditions.
- Development of a short-term assay based on the evaluation of the plasma membrane integrity of the alga Pseudokirchneriella subcapitataPublication . Machado, Manuela D.; Soares, Eduardo V.Membrane integrity has been used as a criterion for the definition of cell viability. In the present work, staining conditions (time and dye concentration) for the evaluation of membrane integrity in a fluorescence microplate reader, using the membrane-impermeant nucleic-acid dye SYTOX Green, were optimized. Incubating Pseudokirchneriella subcapitata algal cells with 0.5 μmol/l SYTOX Green for 40 min allowed a clear discrimination between live (intact plasma membrane) and dead cells (with compromised plasma membrane). Algal cell suspensions, labelled with SYTOX Green, exhibited a green fluorescence proportional to the fraction of the cells with a permeabilized plasma membrane. The optimized staining conditions were used to assess the toxicity of 1-pentanol on P. subcapitata in a short-term exposure (6 h) assay. The loss of membrane integrity in the cell population increased with the concentration of 1-pentanol. The 6-h EC10 and EC50 values were 7,617 mg/l 1-pentanol (95 % confidence limits 4,670–9,327) and 12,818 mg/l 1-pentanol (95 % confidence limits 10,929–15,183), respectively. The developed microplate-based short-term assay can be useful in the highthroughput screening of toxics or environmental samples using the alga P. subcapitata.
- Editorial: Bio-based solutions for sustainable development of agriculture, volume IIPublication . Soares, Eduardo V.; Petropoulos, Spyridon A.; Soares, Helena M. V. M.; Vasconcelos, Marta[editorial excerpt] The modern cropping industry has to address food security challenges related to the increasing world population, the pressure of climate change on crop production, and the adverse effects of anthropogenic activities on agro-ecosystems (Boix-Fayos and de Vente, 2023; Grigorieva et al., 2023). Therefore, various strategies have been suggested (e.g. Green Deal, Soil Deal, Farm to Fork, and European Biodiversity) focusing on a gradual and mild transition toward sustainable cropping systems and agronomic solutions. Biostimulants and bio-based solutions in general have been considered viable solutions to be integrated into the current agronomic schemes to overcome the challenges that the cropping sector is facing or is expected to face in the near future.