Sensitivity of freshwater and marine green algae to three compounds of emerging concern

In this study, the toxicity of three compounds of emerging concern (CEC) belonging to different classes [metolachlor (herbicide), erythromycin (antibiotic) and triclosan (antiseptic)], were evaluated and compared using the freshwater alga Pseudokirchneriella subcapitata and the marine alga Dunaliella tertiolecta. Toxicity assays were performed by exposing algal cells, in exponential phase of growth, to the toxicants for 72 h (P. subcapitata) or 96 h (D. tertiolecta). The toxicant concentrations that induced an inhibition of 50% of algal growth (EC50) of P. subcapitata or D. tertiolecta were 118 and 11.3×103 g L1 for metolachlor (MTC), 38 and 5.75×103 g L1 for erythromycin (ERT) and 27.1 and 93 g L1 for triclosan (TCS), respectively. Based on these EC50 values, it was possible to hierarchize (decreasing order) the toxicity of the CEC studied: TCS>ERT>MTC. The EC50 values achieved for P. subcapitata were between 3.4- and 151-fold lower than those observed with D. tertiolecta, which demonstrated the higher sensitivity of the freshwater alga comparatively to the marine alga. All 72 h-EC10 or 72 h-EC50 values determined in this study with P. subcapitata are within the concentration range of these pollutants described in the literature, in ground and surface waters, which underlines the significance of this alga in the ecotoxicity assessment of freshwaters.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte. Manuela D. Machado gratefully acknowledges the post-doctoral grant from FCT (SFRH/BPD/72816/2010).info:eu-repo/semantics/publishedVersio

Toxic effects of erythromycin to freshwater and marine microalgae

[Excerpt] Erythromycin (ERT) is a macrolide antibiotic frequently used in human and animal health care to combat bacterial infections and in aquaculture and livestock as growth promoter. A high part of the administered ERT is not adsorbed being eliminated to wastewater treatment plants where is not effectively removed/degraded [1]. Therefore, ERT has been found in aquatic systems (at ng L-1 to µg L-1) [2]. However, the knowledge of ERT impact to non-target organisms is limited. Microalgae, as primary producers, are one of the first organisms to be in contact with aquatics contaminants. Thus, it is of emerging concern to study the impact of ERT in freshwater and marine microalgae. In this study, it was evaluated the impact of ERT on the growth of the freshwater alga Pseudokirchneriella subcapitata (during 72 h) and of the marine Dunaliella tertiolecta (during 96 h). EC10 of 5 and 1880 µg L-1 and EC50 of 38 and 5745 µg L-1 were obtained for P. subcapitata and D. tertiolecta, respectively. So, the freshwater alga P. subcapitata presented a higher sensitivity (ppb level) to ERT than marine one (ppm level). [...]info:eu-repo/semantics/publishedVersio

Toxicological effects induced by the biocide triclosan on Pseudokirchneriella subcapitata

Triclosan, a widely used biocide broadly found in aquatic environments, is cause of concern due to its unknown effects on non-targets organisms. In this study, a multi biomarker approach was used in order to evaluate the 72?h-effect of triclosan on the freshwater alga Pseudokirchneriella subcapitata. Triclosan, at environmental relevant concentrations (27 and 37?µg L-1), caused a decrease of proliferative capacity, which was accompanied by an increase of cell size and a profound alteration of algae shape. It was found that triclosan promoted the intracellular accumulation of reactive oxygen species, the depletion of non-enzymatic antioxidant defenses (reduced glutathione and carotenoids) and a decrease of cell metabolic activity. A reduction of photosynthetic pigments (chlorophyll a and b) was also observed. For the highest concentration tested (37 µg L-1), a decrease of photosynthetic efficiency was detected along with a diminution of the relative transport rate of electrons on the photosynthetic chain. In conclusion, triclosan presents a deep impact on the microalga P. subcapitata morphology and physiology translated by multiple target sites instead of a specific point (cellular membrane) observed in the target organism (bacteria). Additionally, this study contributes to clarify the toxicity mechanisms of triclosan, in green algae, showing the existence of distinct modes of action of the biocide depending on the microalga.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2020 unit and BioTecNorte operation (NORTE-01-0145- FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Microwave-assisted generation and reactivity of aza- and diazafulvenium methides: heterocycles via pericyclic reactions

Azafulvenium methides and diazafulvenium methides have been generated under microwave irradiation from 2,2-dioxo-1H,3H-pyrrolo[1,2-c]thiazoles and 2,2-dioxo-1H,3H-pyrazolo[1,5-c]thiazoles, respectively. Pericyclic reactions of these 1,7-dipole intermediates, namely, sigmatropic [1,8]H shifts, 1,7-electrocyclization or [8[pi]+2[pi]] cycloaddition led to the synthesis of a range of pyrrole and pyrazole derivatives. The first evidence for the azafulvenium methides by intermolecular trapping via [8[pi]+2[pi]] cycloaddition is reported.http://www.sciencedirect.com/science/article/B6THS-4SP3SM3-6/1/d6303d9db78919cfe9cd796c1a17d44

New chemistry of diazafulvenium methides: one way to pyrazoles

Diazafulvenium methides generated from the solution pyrolysis of pyrazolo[1,5-c][1,3]thiazole-2,2-dioxides participate in [8[pi]+2[pi]] cycloadditions giving pyrazolo[1,5-a]pyridine derivatives. 1-Methyl-diazafulvenium, generated under flash vacuum pyrolysis reaction conditions, undergoes an intramolecular sigmatropic [1,8]H shift giving 1-vinyl-1H-pyrazoles.http://www.sciencedirect.com/science/article/B6THS-4HR7298-7/1/af0dd8d679e7977f53bc0d4af9a5b68

The amino acids motif-32GSSYN36-in the catalytic domain of E. coli flavorubredoxin NO reductase is essential for its activity

Funding Information: Funding: This study was financially supported by the Portuguese Fundação para a Ciência e Tec-nologia (FCT), grants PTDC/BIA-BQM/27959/2017 and PTDC/BIA-BQM/0562/2020, and Project MOSTMICRO-ITQB with references UIDB/04612/2020 and UIDP/04612/2020. This project has also received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement 810856. MCM is the recipient of FCT grant SFRH/BD/143651/2019. BAS is the recipient of FCT grant DFA/BD/8066/2020. Funding Information: This study was financially supported by the Portuguese Funda??o para a Ci?ncia e Tecnologia (FCT), grants PTDC/BIA-BQM/27959/2017 and PTDC/BIA-BQM/0562/2020, and Project MOSTMICRO-ITQB with references UIDB/04612/2020 and UIDP/04612/2020. This project has also received funding from the European Union?s Horizon 2020 research and innovation program under grant agreement 810856. MCM is the recipient of FCT grant SFRH/BD/143651/2019. BAS is the recipient of FCT grant DFA/BD/8066/2020. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Flavodiiron proteins (FDPs) are a family of modular and soluble enzymes endowed with nitric oxide and/or oxygen reductase activities, producing N2O or H2O, respectively. The FDP from Escherichia coli, which, apart from the two core domains, possesses a rubredoxin-like domain at the C-terminus (therefore named flavorubredoxin (FlRd)), is a bona fide NO reductase, exhibiting O2 reducing activity that is approximately ten times lower than that for NO. Among the flavorubredoxins, there is a strictly conserved amino acids motif,-G[S,T]SYN-, close to the catalytic diiron center. To assess its role in FlRd’s activity, we designed several site-directed mutants, replacing the conserved residues with hydrophobic or anionic ones. The mutants, which maintained the general characteristics of the wild type enzyme, including cofactor content and integrity of the diiron center, revealed a decrease of their oxygen reductase activity, while the NO reductase activity—specifically, its physiological function—was almost completely abolished in some of the mutants. Molecular modeling of the mutant proteins pointed to subtle changes in the predicted structures that resulted in the reduction of the hydration of the regions around the conserved residues, as well as in the elimination of hydrogen bonds, which may affect proton transfer and/or product release.publishe

A novel samarium(II) complex bearing a dianionic bis(phenolate) cyclam ligand: synthesis, structure and electron-transfer reactions

A novel divalent samarium complex anchored on a dianionic bis(phenolate) ligand is reported and reactivity studies demonstrate that it is highly effective in inducing single-electron transfer processes.</p

Rammed earth construction with granitic residual soils: the case study of northern Portugal

Building in unstabilised rammed earth results in low environmental impact. However, northern Portugal has not historical tradition with this technique, and thus the suitability of the local granitic residual soils is unknown. This paper presents an experimental investigation, where this possibility is assessed. The results showed that these soils are unsuitable, and that rammed earth construction is only feasible if these soils go through a stabilising process. The alkaline activation of fly ash was investigated as an environmentally friendly stabilisation technique, and it proved to be capable of improving the performance of rammed earth

The use of muscle biomarkers for assessing physiological effects of heavy metal pollution in the greater white-toothed shrew (Crocidura russula)

The greater white-toothed shrew Crocidura russula has been used as a sentinel species for estimating environmental risks to human populations. Previous studies in mining areas have focused on the liver of shrews as the primary target of physiological and metabolic changes due to heavy metal pollution. However, populations persist even when detoxification by the liver seems to be compromised and damage is observed. These pollutant-adapted individuals inhabiting contaminated sites may exhibit altered biochemical parameters that confer increased tolerance in various tissues other than the liver. The skeletal muscle tissue of C. russula might be an alternative tissue that allows the survival of organisms inhabiting historically polluted sites due to the detoxification of redistributed metals. Organisms from two heavy metal mine populations and one population derived from an unpolluted site were used to determine the detoxification activities, antioxidant capacity, and oxidative damage, as well as cellular energy allocation parameters and acetylcholinesterase activity (a biomarker of neurotoxicity). Muscle biomarkers differ between shrews from polluted sites and shrews from the unpolluted location, with the mine animals showing: (1) a decreased energy consumption concomitant with increased energy reserves and total available energy; (2) reduced cholinergic activity, suggesting an impairment of neurotransmission at the neuromuscular junction; (3) an overall decrease in detoxification capacity and enzymatic antioxidant response and a higher level of lipid damage. Also, some of these markers differed between females and males. These changes may have resulted from a decreased detoxifying capacity of the liver and could potentially bring about significant ecological effects for this highly active species. Heavy metal pollution induced physiological changes in Crocidura russula showing that skeletal muscle may serve as a backup sink organ allowing rapid species adaptation and evolution.publishe

Produção simultânea de -fructofuranosidase e fructo-oligossacarídeos por Penicillium citreonigrum URM 4459

O objetivo deste trabalho foi a produção simultânea de -Frutofuranosidase (FFase) e frutooligossacarídeos (FOS) por P. citreonigrum utilizando um planejamento fatorial completo. Para isso, o fungo foi cultivado em meio rico em sacarose (20% p/v) a 150 rpm. As condições de tempo de fermentação, temperatura, pH e concentração de extrato de levedura foram definidas utilizando um planejamento fatorial. Ao fim da fermentação, o sobrenadante obtido por filtração foi utilizado para quantificação de FFase e FOS. Todas as variáveis independentes estudadas exerceram efeito estatisticamente significativo sob a produção de FFase. Por outro lado, apenas as variáveis tempo de fermentação e temperatura exerceram efeito significativo sob a produção do FOS. As condições ideais para produção simultânea de FFase e FOS foram obtidas na região dos pontos centrais, onde obteve-se uma produção média de 93,49 g/L de FOS e uma atividade de 260,40 U/mL de FFase