Quorum sensing influences growth and photosynthetic membrane production in high-cell-density cultivations of Rhodospirillum rubrum

BACKGROUND: The facultative anoxygenic photosynthetic bacterium Rhodospirillum rubrum exhibits versatile metabolic activity allowing the adaptation to rapidly changing growth conditions in its natural habitat, the microaerobic and anoxic zones of stagnant waters. The microaerobic growth mode is of special interest as it allows the high-level expression of photosynthetic membranes when grown on succinate and fructose in the dark, which could significantly simplify the industrial production of compounds associated with PM formation. However, recently we showed that PM synthesis is no longer inducible when R. rubrum cultures are grown to high cell densities under aerobic conditions. In addition a reduction of the growth rate and the continued accumulation of precursor molecules for bacteriochlorophyll synthesis were observed under high cell densities conditions. RESULTS: In the present work, we demonstrate that the cell density-dependent effects are reversible if the culture supernatant is replaced by fresh medium. We identified six N-acylhomoserine lactones and show that four of them are produced in varying amounts according to the growth phase and the applied growth conditions. Further, we demonstrate that N-acylhomoserine lactones and tetrapyrrole compounds released into the growth medium affect the growth rate and PM expression in high cell density cultures. CONCLUSIONS: In summary, we provide evidence that R. rubrum possesses a Lux-type quorum sensing system which influences the biosynthesis of PM and the growth rate and is thus likely to be involved in the phenotypes of high cell density cultures and the rapid adaptation to changing environmental conditions

Democratic Management in Times of COVID-19:: Perspectives and Challenges for Brazilian Public Schools

This paper discusses the issue of educational management in a challenging scenario: the closing of Brazilian schools due to the COVID-19 pandemic. Through an exploratory research, in a documentary character, the articulating role that educational management has been developing together with the families of students was evaluated, with the aim to guarantee their access to remote activities during this period, and their maintenance and organization by part of higher departments. Under the clipping of two official documents of the state of Rio de Janeiro, Deliberation No. 376 of the State Council of Education of the state and Resolution No. 5843 of the Secretary of State for Education, it was possible to identify a greater concern with access to content, either through technological mediation or printed material and with “supervision” of teachers and students, to the detriment of strengthening aspects relevant to democratic and participatory management. No references to management or direction were found in the documents under analysis, nor ways to consolidate the participation of all actors involved in the teaching-learning process. The absence of dialogicity with all parties led us to a traumatic and exhausting process for everyone involved. Therefore, the need to rethink the pedagogical practices involved in this pandemic period is discussed, based on the difficulties listed by students, families, teachers and managers, in order to consolidate the contribution of all, in a democratic way, even if there is no social interaction between those involved at the time

Teaching Practices in Mathematics During COVID-19 Pandemic: Challenges for Technological Inclusion in a Rural Brazilian School

The pandemic caused by COVID-19, on a global scale, brought an unprecedented situation for students from all over the world: the closure of schools. This study presents this theme under the perspective of a rural Brazilian school, located in a town in the interior of the state of Rio de Janeiro. Since the closure of schools as a health strategy for the control of the pandemic, the government of the state of Rio de Janeiro adopted the distance learning for school activities, most of which was achieved through technological mediation. This strategy to face the problem highlight reflections on inequality of access to the internet and the different roles played by the school, in addition to cognitive aspects. Considering as a research object the class of ninth grade of elementary school, and as a research theme their mathematics activities in distance learning, it was possible, through a case study, to analyze advances and setbacks in the learning proposal implemented. It is concluded that Brazil, due to its extensive territorial range and multiple specificities, is not yet prepared to legitimize the use of pedagogical practices in mathematics mediated by technology. Investments in infrastructure and teacher training are necessary so that pedagogical proposals mediated by technology can effectively contribute to the training of students

Mango Dermatitis After Urushiol Sensitization

Prior exposure to poison ivy and poison oak, which are plants in the Anacardiacea family and contain high levels of urushiol, appear to be a risk factor for delayed hypersensitivity reactions to mango fruits. Cross-sensitization between these plants and mangos is believed to be secondary to an overlap in the urushiol antigen and 5-resorcinol, found predominately in mango peels. This unique combination of sensitization and reaction constitutes a type IV hypersensitivity response, mediated and driven by T cells reacting to similar antigens. We present a case of an otherwise healthy man, with a remote history of poison ivy exposure, who presented with a delayed but significant reaction to mango fruit. Obtaining the patient’s history of prior plant exposures and reactions was key to isolating the likely underlying causation of his presentation

Fake News and Post-truth: Numerical Simulations of Information Diffusion in Social Networks

The year 2016 was crucial in terms of the use of social networks as tools for disseminating information for political purposes. The election of candidate Donald Trump for the presidency of the United States of America lit a warning signal about the influence that the information disseminated through social networks exerted in the choice of candidates by the American people. Since then, researchers from different areas have focused on the topic, which involves different aspects: computing, social sciences, mathematics, among others. Therefore, the object of study of this work is the phenomenon of behavioral changes brought about by the new social relationships established by digital social networks, under the scope of the spread of fake news through them. To guarantee the intended study, the general objective was to adapt mathematical models consisting of ordinary differential equations for the dissemination of information on social networks for the spread of fake news. As specific objectives, the contribution of the mathematical models proposed in the mitigation, through algorithms, of the spread of false or distorted information was discussed, as well as the discussion on the concepts of fake news and post-truth from a social point of view, in a way that individuals can also distinguish true information from disinformation through individual interpretation tools. As a research methodology, bibliographic research was chosen and a systematic literature review was carried out, to consider published works on the proposed research object. For the numerical simulations, a numerical code was developed in MATLAB, which was able to carry out the desirable experiments. It is concluded that innovation diffusion models can adapt to fake news dissemination models. However, such models are not able to robustly simulate the mitigation of fake news