Toxicity of metals in aquatic hyphomycetes : cellular targets and defense mechanisms

Tese de Doutoramento em CiênciasHuman activities contribute to a high release of heavy metals to the environment at rates and concentrations sufficient to make them pollutants. Certain metals, such as Cu and Zn, are needed for the growth and metabolism of organisms, while others, as Cd, have no recognized biological functions. However, above critical levels, both essential and non-essential metals became toxic to living organisms. Aquatic hyphomycetes are a polyphyletic group of fungi that play a key role in plant-litter decomposition in streams. They produce an array of exoenzymes able to degrade plant cell-wall polymers and increase plant-litter palatability for invertebrate detritivores. Even though these fungi occur in metal-polluted streams, the mechanisms underlying their resistance/tolerance to metals are poorly documented. In this study, the exposure to metals inhibited reproduction, as sporulation rates, of the aquatic hyphomycetes. Moreover, fungal reproduction was more sensitive to metals than growth. The sensitivity of aquatic hyphomycetes to metals, assessed as the metal concentration inhibiting biomass production in 50% (EC50), showed that Ypsilina graminea and Varicosporium elodeae were the most resistant species to Zn, while Heliscus submersus was the most resistant to Cu. The EC50 values were about 20-times higher in solid medium than in liquid medium. However, the patterns of species resistance to metals in either liquid or solid medium, with similar composition, were identical. Generally, Ni or Cd were more toxic than Zn or Cu to fungi. H. submersus and V. elodeae had remarkable ability to adsorb Cu and Zn, respectively. Because these fungal species were highly tolerant to each metal, biosorption may be a relevant mechanism to avoid unrestrained uptake of metals. We demonstrated that the generation/accumulation of reactive oxygen species (ROS) contributed noticeably to metal toxicity in aquatic hyphomycetes, particularly under Cu stress, as indicated by a recovery in biomass production by the presence of an antioxidant agent. Our results showed that plasma membrane integrity of V. elodeae and H. submersus was more affected by Cu than Zn, pointing to this cellular structure as a potentially vulnerable target of Cu. At short-term (10 min), Cu completely inhibited the activity of the plasma membrane H+-ATPase of H. submersus and V. elodeae, while Zn only led to a similar effect on that of H. submersus. However, a recovery of plasma membrane integrity was observed after 150 min of metal exposure. A strong stimulation of the proton pump was found in the most tolerant species (i.e. when H. submersus was exposed to Cu and V. elodeae was exposed to Zn) at longer times (8 days). The activation of H+-ATPase may contribute to counteract metal-induced dissipation of the electrochemical gradient of protons across the plasma membrane, suggesting that H+- ATPase may be involved in aquatic hyphomycete acclimation to metals. Our studies on antioxidant defenses showed that catalase had a greater role in alleviating the stress induced by Cu and Zn than superoxide dismutase. In addition, the increased activity of glucose-6-phosphate dehydrogenase, after long-term exposure to metals (8 days), points to the involvement of the pentose phosphate pathway in metal acclimation. Before metal exposure, H. submersus and Flagellospora curta isolated from a metal-polluted stream had higher levels of thiol compounds than V. elodeae, isolated from a clean stream. However, the latter species rapidly increased the levels of thiols after metal exposure. These findings are in agreement with the recognized role of thiol compounds as metal sequesters and/or ROS scavengers. Finally, we showed that Cu and Zn are able to induce programmed cell death (PCD) in aquatic hyphomycetes, a process in which cells actively participate in their own death. The exposure to Cu promoted ROS production and caspase activation in H. submersus and F. curta. Conversely, under Zn stress, aquatic hyphomycetes showed high number of cells with nuclear morphological alterations and/or DNA strand-breaks. The different pattern of PCD markers suggests that the triggering cell death signal is most probably related to different cellular targets for Cu and Zn in aquatic hyphomycetes.As actividades humanas contribuem para o aumento da libertação de metais pesados para o ambiente, a taxas e a concentrações que os tornam poluentes. Alguns metais, como o Cu e o Zn, são necessários para o crescimento e metabolismo dos organismos, enquanto que outros, como o Cd, não lhes é atribuída qualquer função biológica. Contudo, acima de certas concentrações, os metais, quer os essenciais quer os não essenciais, tornam-se tóxicos para os organismos vivos. Os hifomicetos aquáticos são um grupo de fungos filogeneticamente heterogéneo que desempenham um papel chave na decomposição dos detritos vegetais nos rios. Estes fungos produzem um conjunto de enzimas extracelulares capazes de degradar os polímeros das paredes das células vegetais aumentando a palatabilidade dos detritos vegetais para os invertebrados detritívoros. Apesar dos hifomicetos aquáticos estarem presentes quer em rios de referência quer em rios poluídos com metais pesados, os mecanismos subjacentes à sua resistência/tolerância aos metais são pouco conhecidos. Neste estudo, a reprodução dos fungos, avaliada pela taxa de esporulação, foi inibida pela exposição aos metais. Além disso, a reprodução dos fungos foi mais sensível aos efeitos negativos dos metais do que o seu crescimento. A sensibilidade dos hifomicetos aquáticos aos metais, avaliada pela concentração de metal capaz de inibir a produção de biomassa em 50% (EC50), mostrou que Ypsilina graminea e Varicosporium elodeae foram as espécies mais resistentes ao Zn, enquanto que Heliscus submersus foi a mais resistente ao Cu. Os valores de EC50 foram cerca de 20 vezes mais elevados em meio sólido do que em meio líquido. Porém, os padrões de resistência aos metais exibidos pelos hifomicetos aquáticos foram semelhantes em meio sólido ou em meioo líquido com idêntica composição química. Geralmente, o Ni ou o Cd foram mais tóxicos do que o Zn ou o Cu. H. submersus e V. elodeae exibiram capacidade elevada para adsorver, respectivamente, Cu e Zn. Dado que estes fungos foram muito tolerantes a esses metais, a bioadsorção pode constituir um mecanismo relevante para controlar a entrada dos metais nas células. Neste trabalho demonstrámos que a produção de espécies reactivas de oxigénio (ROS) contribuiu notavelmente para a toxicidade dos metais, sobretudo no caso do Cu, como indicado pela recuperação da biomassa produzida pelos fungos na presença de um agente antioxidante. A integridade da membrana plasmática de V. elodeae e de H. submersus foi mais afectada pelo Cu do que pelo Zn, sugerindo que esta estrutura celular pode ser um alvo potencial para o Cu. A tempos curtos de exposição (10 min), o Cu bloqueou a actividade da H+-ATPase da membrana plasmática de H. submersus e de V. elodeae, enquanto que o Zn só promoveu um efeito semelhante em H. submersus. Contudo, uma recuperação da integridade da membrana plasmática foi observada a tempos mais longos (150 min). Após 8 dias de exposição, um estímulo forte da bomba de protões foi encontrado nas espécies mais tolerantes, i.e. em H. submersus exposto a Cu e em V. elodeae exposto a Zn. A activação da H+-ATPase pode contribuir para contrabalançar a dissipação do gradiente electroquímico de protões induzida pelo metal, sugerindo o envolvimento desta bomba na aclimatação dos fungos ao stress metálico. Os nossos estudos sobre as defesas antioxidantes mostraram que a catalase teve um papel mais importante do que a superóxido dismutase na mitigação do stress induzido pelo Cu e pelo Zn. Além disso, o estímulo da actividade da glucose-6-fosfato desidrogenase após 8 dias de exposição aos metais, sugere o envolvimento da via das pentoses na aclimatação dos fungos aos metais. As espécies H. submersus e Flagellospora curta, isoladas de um rio poluído com metais, tinham níveis mais elevados de compostos ricos em grupos tiol do que a espécie V. elodeae, isolada de um rio de referência. Contudo, esta última espécie aumentou rapidamente o seu conteúdo em compostos tiólicos após a exposição ao metal. Estes resultados estão de acordo com o reconhecido papel dos compostos tiólicos na sequestração de metal e/ou ROS nas células. Finalmente, os nossos resultados mostraram que o Cu e o Zn foram capazes de induzir morte celular programada (PCD) em hifomicetos aquáticos, um processo de morte celular activa. O stress induzido pelo Cu estimulou sobretudo a produção de ROS e a actividade das caspases em H. submersus e em F. curta. Por outro lado, os hifomicetos aquáticos expostos a Zn mostraram um elevado número de células com alterações morfológicas no núcleo e/ou quebras na cadeia de DNA. O diferente padrão de resposta dos marcadores de PCD sugere que o sinal de morte celular pode estar relacionado com diferentes alvos celulares do Cu e do Zn em hifomicetos aquáticos

Microbes and cancer: friends or faux?

Cancer is one of the most aggressive and deadly diseases in the world, representing the second leading cause of death. It is a multifactorial disease, in which genetic alterations play a key role, but several environmental factors also contribute to its development and progression. Infections induced by certain viruses, bacteria, fungi and parasites constitute risk factors for cancer, being chronic infection associated to the development of certain types of cancer. On the other hand, susceptibility to infectious diseases is higher in cancer patients. The state of the host immune system plays a crucial role in the susceptibility to both infection and cancer. Importantly, immunosuppressive cancer treatments increase the risk of infection, by decreasing the host defenses. Furthermore, alterations in the host microbiota is also a key factor in the susceptibility to develop cancer. More recently, the identification of a tumor microbiota, in which bacteria establish a symbiotic relationship with cancer cells, opened a new area of research. There is evidence demonstrating that the interaction between bacteria and cancer cells can modulate the anticancer drug response and toxicity. The present review focuses on the interaction between microbes and cancer, specifically aiming to: (1) review the main infectious agents associated with development of cancer and the role of microbiota in cancer susceptibility; (2) highlight the higher vulnerability of cancer patients to acquire infectious diseases; (3) document the relationship between cancer cells and tissue microbiota; (4) describe the role of intratumoral bacteria in the response and toxicity to cancer therapy.This research was funded by National Funds through FCT—Fundação para a Ciência e a Tecnologia, I.P., within CINTESIS, R&D Unit, grant number UIDB/4255/2020

Portuguese students' knowledge of antibiotics: a cross-sectional study of secondary school and university students in Braga

<p>Abstract</p> <p>Background</p> <p>Recent surveys show that the knowledge of the general public about the correct use of antibiotics is limited. This contributes to the problem of inappropriate antibiotic use, leading to a progressive loss of bacterial sensitivity to these drugs and the spreading of resistant strains of bacteria.</p> <p>Methods</p> <p>In this cross-sectional study, a questionnaire about antibiotic use was given to a sample of students in the 9^thand 12^thgrades of secondary school and in the first year of university in the north of Portugal.</p> <p>Results</p> <p>349 students returned completed questionnaires. Deficits were found in the students' knowledge of antibiotics and their correct use. Only 4% of 9^thgrade students were aware that antibiotics are used to treat bacteria only, while 14% of 12^thgrade students and 29% of first-year university students were aware of this. Fewer students were aware that antibiotics are used to treat tuberculosis. There were deficiencies in the knowledge of timing and duration of therapy. However close to 70% of these students are aware that inappropriate use of antibiotics can contribute to resistance to these drugs.</p> <p>Conclusion</p> <p>This study has observed a lack of general knowledge on correct antibiotic use in Portugal, as has been found in other countries. Since this may be due to a lack of formal education on this subject, we believe that a teaching unit on infectious diseases should be included in the 9^thand 12^thgrades, in all curricular areas, with emphasis on bacterial and viral pathogens and correct antibiotic use. In addition, education on the correct use of medications may need to begin at much earlier ages.</p

Impact of educational gardens and workshop activities on 8th-Grade student’s perception and knowledge of plant biology

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/educsci12090619/s1, Supplementary Data S1. Dichotomous key for the Atlantic garden; Supplementary Data S2. Dichotomous key for the Lowland Mediterranean garden; Supplementary Data S3. Dichotomous key for the Mountain Mediterranean garden; Supplementary Data S4. Full pre-validated questionnaire for quantitative assessment of student knowledge gain; Supplementary Data S5. Performance in each question of the experimental and control groups, in both the pre- and post-test questionnaires; Supplementary Data S6. Scores for the pre-test and post-test in both control and experimental groups; Supplementary Figure S1. Construction of three educational gardens within the grounds of School EB 2/3 D. Maria II.Educational gardens can be a significant resource in the promotion of environmental education, engaging both the school population and the general public. The main goal of the present study was to implement and assess a hands-on interventional program to promote knowledge and awareness of plant-related topics at a basic school level. We report on a hands-on educational project implemented with 8th-grade Portuguese students (mostly 13–14 years of age), associated with the establishment, on school grounds, of three educational gardens representing distinct Portuguese ecosystems. This was a collaborative project and encompassed several activities and subjects, including garden creation, plant propagation and plant care, plant identification, the study of form–function relationships, and lectures by plant researchers. A survey instrument with pre- and post-test assessments demonstrated the effectiveness of the program in raising student knowledge and awareness on topics centered around the native flora. Specifically, we noted that scores increased in all questions addressing different plant biology-related topics in the post-test assessment. This study supports the benefits of incorporating field/laboratory work and educational gardens in educational programs geared toward plant-oriented environmental education.The present work was supported by the Pais com a Ciência Program, of the Agency Ciência Viva—Agência Nacional para a Cultura Científica e Tecnológica, in collaboration with CONFAP (Confederação Nacional das Associações de Pais). This work was also supported by Fundação Ilídio Pinho, Porto, Portugal. H.A. was supported by Fundação para a Ciência e Tecnologia (FCT/MCTES) ref. CEECIND/00399/2017/ CP1423/CT0004], and NORTE 2020 through FEDER, ref. [NORTE-01-0145-FEDER-000007]. I.S-S. was supported by the program contract FCTUMINHO/Norma transitória from the Legal Regime of Scientific Employment (RJEC) and by the strategic program UID/BIA/04050/2020)

The impact of alternative science education methodologies on the motivation and acquisition of scientific concepts

Fully aware of the increasing importance of active and experimental learning, this study has been conducted in Portugal between 2007 and 2008 and was the first of this kind to ever be conducted in this country. Thirty eight students of the school E.B. 2, 3 D. Maria II (middle school) participated in the extra-curricular activity entitled “Scientists for a Day”, previous developed by the Life and Health Science Research Institute/School of Health Science (ICVS/ECS), University of Minho. This activity realized in the School E.B. 2, 3 D. Maria II and organized by teachers of the same School consisted in a set of laboratory activities subdivided into four experimental stations, namely: 1st Station – “Extracting banana DNA”; 2nd Station – “Acid/Base”, 3rd Station – “Observation of chicken embryos” and 4th Station – “Five Senses”. The general objectives of this activity were to stimulate the pleasure of knowledge, encourage critical views, heighten the interest in science, motivate students towards experimental work and demystify the idea of what a Scientist is. In an effort to validate this activity and evaluate what they have learned, the students were asked to answer a questionnaire before and immediately after this activity. In this study we observed a clear correlation between the use of active and experimental learning activities, and an increase in scientific knowledge

The Use of ARM-Assembly Language and a Raspberry Pi 1 B+ as a Server to Improve Computer Architecture Skills

UIDB/03213/2020 UIDP/03213/2020Prompting students' interest and engagement in learning environments is crucial to achieve the best results. Academia and educators in general are constantly adapting materials and methodologies in order to maximise the acquisition of contents by their students. In this case-study, a new teaching/learning methodology is presented and evaluated through a final questionnaire survey. This case-study aims to understand students' efficiency and motivation levels regarding a new teaching/learning methodology adopted in the second module of a Computer Systems and Architectures course attended by first-year Computer Sciences undergraduates. The new teaching/learning methodology relies on a specific programming language-ARMv6 assembly-to improve students' efficiency levels, and an innovative always-visible in-class mobile test scenario, implemented through a low-cost computing platform-Raspberry Pi 1 B+- A s a server, mimicking as much as possible a real-life environment, so that students believe they are working on real hardware, thus enhancing their motivation levels. The results of the questionnaire survey allowed to infer that the use of a specific programming language, such as ARMv6 assembly, coupled with a new always-visible in-class mobile test scenario were in fact efficient in raising the levels of motivation among Computer Sciences students and, consequently, improved their skills in Computer Architecture. 2012 ACM Subject Classification Computer systems organization.publishersversionpublishe

Impact of an educational hands-on project on the antimicrobial, antitumor and anti-inflammatory properties of plants on Portuguese students' awareness, knowledge, and competences

Promoting environmental and health education is crucial to allow students to make conscious decisions based on scientific criteria. The study is based on the outcomes of an Educational Project implemented with Portuguese students and consisted of several activities, exploring pre-existent Scientific Gardens at the School, aiming to investigate the antibacterial, antitumor and anti-inflammatory properties of plant extracts, with posterior incorporation in soaps and creams. A logo and a webpage were also created. The effectiveness of the project was assessed via the application of a questionnaire (pre- and post-test) and observations of the participants in terms of engagement and interaction with all individuals involved in the project. This project increased the knowledge about autochthonous plants and the potential medical properties of the corresponding plant extracts and increased the awareness about the correct design of scientific experiments and the importance of the use of experimental models of disease. The students regarded their experiences as exciting and valuable and believed that the project helped to improve their understanding and increase their interest in these subjects and in science in general. This study emphasizes the importance of raising students’ awareness on the valorization of autochthonous plants and exploitation of their medicinal properties.Study was supported by Fundação Ilídio Pinho, Porto, Portuga

Noise in an Intensive Care Nursery/Newborn Unit

info:eu-repo/semantics/publishedVersio