Estabelecimento de uma cultura de tardígrados limno-terrestres em laboratório e desenvolvimento de metodologias alternativas de desidratação de tardígrados

Tardígrados (Filo Tardigrada) são animais invertebrados conhecidos como ursos d’água, que existem em quase todas as localidades do planeta, encontrados do Ártico até a Antártida, alto do Himalaia até 6000 m de profundidade oceânica. A presença dos animais em ambientes tão diversos se deve à sua capacidade de entrar em criptobiose, estado induzido por condições adversas, no qual os animais sobrevivem à desidratação, temperaturas de -192 °C até acima de 100 °C, pressão de 7500 Pa, níveis de radiações de 7000 Gy, entre outras condições. Atualmente, o filo tem sido mais  investigado, em razão da sua capacidade de tolerar condições extremas, as quais são interessantes do ponto de vista biotecnológico. Também possui importância para estudos de filogenia de metazoários, estudos de evolução e tambem para a astrobiologia. Não existem relatos de trabalhos de criptobiose e cultivo dos animais no país, sendo o primeiro do gênero. O trabalho buscou estabelecer uma cultura de tardígrados limno-terrestres em laboratório, isolados da natureza e também encontrar metodologias alternativas ao uso de dessecadores químicos para a desidratação e testes de anidrobiose. Estabeleceu-se com sucesso um cultivo do tardígrado Macrobiotus hufelandi, utilizando-se a microalga Chlorella vulgaris como alimento, em pequenos recipientes plásticos de aproximadamente 30 mm de diâmetro e 20 mm de altura, realizando-se a troca do alimento e da água a cada dois dias. As metodologias de desidratação propostas alcançaram índices de sobrevivência de 70 e 77,73%, similares aos relatados na literatura, podendo constituir alternativas mais simples para estudos com anidrobiose. Palavras chave: Tardigrada. Cultivo em laboratório. Criptobiose. Desidratação

Physical mechanisms of ESCRT-III-driven cell division.

Living systems propagate by undergoing rounds of cell growth and division. Cell division is at heart a physical process that requires mechanical forces, usually exerted by assemblies of cytoskeletal polymers. Here we developed a physical model for the ESCRT-III-mediated division of archaeal cells, which despite their structural simplicity share machinery and evolutionary origins with eukaryotes. By comparing the dynamics of simulations with data collected from live cell imaging experiments, we propose that this branch of life uses a previously unidentified division mechanism. Active changes in the curvature of elastic cytoskeletal filaments can lead to filament perversions and supercoiling, to drive ring constriction and deform the overlying membrane. Abscission is then completed following filament disassembly. The model was also used to explore how different adenosine triphosphate (ATP)-driven processes that govern the way the structure of the filament is changed likely impact the robustness and symmetry of the resulting division. Comparisons between midcell constriction dynamics in simulations and experiments reveal a good agreement with the process when changes in curvature are implemented at random positions along the filament, supporting this as a possible mechanism of ESCRT-III-dependent division in this system. Beyond archaea, this study pinpoints a general mechanism of cytokinesis based on dynamic coupling between a coiling filament and the membrane

Isolation of Uncultured Bacteria from Antarctica Using Long Incubation Periods and Low Nutritional Media

Uncultured microorganisms comprise most of the microbial diversity existing on our planet. Despite advances in environmental sequencing and single-cell genomics, in-depth studies about bacterial metabolism and screening of novel bioproducts can only be assessed by culturing microbes in the laboratory. Here we report uncultured, or recalcitrant, microorganisms from an Antarctic soil sample, using relatively simple methods: oligotrophic media, extended incubation periods, observation under stereo microscopy, and selection of slow-growing bacteria. We managed to isolate several rare microorganisms belonging to infrequently isolated or recently described genera, for example Lapillicoccus, Flavitalea, Quadrisphaera, Motilibacter, and Polymorphobacter. Additionally, we obtained isolates presenting 16S rRNA sequence similarity ranging from 92.08 to 94.46% with any other known cultured species, including two distinct isolates from the class Thermoleophilia, that although common in Antarctic soils (as identified by metagenomics), was never reported to be isolated from such samples. Our data indicates that simple methods are still useful for cultivating recalcitrant microorganisms, even when dealing with samples from extreme environments

Physical mechanisms of ESCRT-III-driven cell division

Living systems propagate by undergoing rounds of cell growth and division. Cell division is at heart a physical process that requires mechanical forces, usually exerted by assemblies of cytoskeletal polymers. Here we developed a physical model for the ESCRT-III-mediated division of archaeal cells, which despite their structural simplicity share machinery and evolutionary origins with eukaryotes. By comparing the dynamics of simulations with data collected from live cell imaging experiments, we propose that this branch of life uses a previously unidentified division mechanism. Active changes in the curvature of elastic cytoskeletal filaments can lead to filament perversions and supercoiling, to drive ring constriction and deform the overlying membrane. Abscission is then completed following filament disassembly. The model was also used to explore how different adenosine triphosphate (ATP)-driven processes that govern the way the structure of the filament is changed likely impact the robustness and symmetry of the resulting division. Comparisons between midcell constriction dynamics in simulations and experiments reveal a good agreement with the process when changes in curvature are implemented at random positions along the filament, supporting this as a possible mechanism of ESCRT-III-dependent division in this system. Beyond archaea, this study pinpoints a general mechanism of cytokinesis based on dynamic coupling between a coiling filament and the membrane

Surviving in hot and cold: psychrophiles and thermophiles from Deception Island volcano, Antarctica

Polar volcanoes harbor unique conditions of extreme temperature gradients capable of selecting different types of extremophiles. Deception Island is a marine stratovolcano located at Maritime Antarctica that is notable for its pronounced temperature gradients over very short distances, reaching values up to 100 °C in the fumaroles, and subzero temperatures next to the glaciers. Due to these characteristics, Deception can be considered an interesting analogue of extraterrestrial environments. Our main goal in this study was to isolate thermophilic and psychrophilic bacteria from sediments associated with fumaroles and glaciers from two geothermal sites in Deception Island, comprising temperatures between 0 and 98 °C, and to evaluate their survivability to desiccation and UV-C radiation. Our results revealed that culturable thermophiles and psychrophiles were recovered among the extreme temperature gradient in Deception volcano, which indicates that these extremophiles remain alive even when the conditions do not comprise their growth range. The viability of culturable psychrophiles in hyperthermophilic environments is still poorly understood and our work showed the importance of future studies about their survival strategies in high temperatures. Finally, the spore-forming thermophilic isolates which we found have displayed good survival to desiccation and UV-C irradiation, which suggests their potential to be further explored in astrobiological studies

Survival of extremophilic yeasts to the stratospheric environment on balloon flights and laboratory simulations

The high-altitude atmosphere is a harsh environment with extremely low temperatures, low pressure, and high UV irradiation. For this reason, it has been proposed as an analogue for Mars, presenting deleterious factors similar to those on the surface of that planet. We evaluated the survival of extremophilic UV-resistant yeasts isolated from a high-elevation area in the Atacama Desert under stratospheric conditions. As biological controls, intrinsically resistant Bacillus subtilis spores were used. Experiments were performed in two independent stratospheric balloon flights and with an environmental simulation chamber. The three following different conditions were evaluated: (i) desiccation, (ii) desiccation plus exposure to stratospheric low pressure and temperature, and (3) desiccation plus exposure to the full stratospheric environment (UV, low pressure, and temperature). Two strains, Naganishia (Cryptococcus) friedmannii 16LV2 and Exophiala sp. strain 15LV1, survived full exposures to the stratosphere in larger numbers than did B. subtilis spores. Holtermanniella watticus (also known as Holtermanniella wattica) 16LV1, however, suffered a substantial loss in viability upon desiccation and did not survive the stratospheric UV exposure. The remarkable resilience of N. friedmannii and Exophiala sp. 15LV1 under the extreme Mars-like conditions of the stratosphere confirms its potential as a eukaryotic model for astrobiology. Additionally, our results with N. friedmannii strengthen the recent hypothesis that yeasts belonging to the Naganishia genus are fit for aerial dispersion, which might account for the observed abundance of this species in high-elevation soils

The patterned assembly and stepwise Vps4-mediated disassembly of composite ESCRT-III polymers drives archaeal cell division

ESCRT-III family proteins form composite polymers that deform and cut membrane tubes in the context of a wide range of cell biological processes across the tree of life. In reconstituted systems, sequential changes in the composition of ESCRT-III polymers induced by the AAA-adenosine triphosphatase Vps4 have been shown to remodel membranes. However, it is not known how composite ESCRT-III polymers are organized and remodeled in space and time in a cellular context. Taking advantage of the relative simplicity of the ESCRT-III-dependent division system in Sulfolobus acidocaldarius, one of the closest experimentally tractable prokaryotic relatives of eukaryotes, we use super-resolution microscopy, electron microscopy, and computational modeling to show how CdvB/CdvB1/CdvB2 proteins form a precisely patterned composite ESCRT-III division ring, which undergoes stepwise Vps4-dependent disassembly and contracts to cut cells into two. These observations lead us to suggest sequential changes in a patterned composite polymer as a general mechanism of ESCRT-III-dependent membrane remodeling. </p

Estágio Supervisionado em Psicologia Escolar: Uma Experiência na Perspectiva Institucional

The theme of the initial formation in Psychology has been motivating a lot of researches and publications in the area of School Psychology, especially aiming at criticality to the formation and consequent performance. This article aims to present supervision actions of a professional internship with emphasis on the formation of the school psychologists. The theoretical assumptions which supported this formation are based on School Critical Psychology and Historic-Cultural Psychology. It will be related experiences of internship with a school psychologist who works in the public education system of Distrito Federal and who develops an institutional role with a focus on collective empowerment and the pursuit of the school success. The actions of the internship sought to strengthen the role of the school psychologist on mediation of the human development and social political changes pressing in the context of public education in the country. This work is expected to contribute to the expansion of the reflections about the commitment with the formation on School Psychology in the graduation through a critical theory-practice articulation, contextualized by the daily praxis of school psychologists and not only those who are in the school.El tema de la formación inicial en Psicología en la graduación viene motivando muchos estudios, repercutiendo también en las producciones relativas a la Psicología Escolar, sobretodo vislumbrando mayor criticidad referente a la formación y actuación. Este artículo tiene como objetivo presentar acciones de supervisión de prácticas profesionales con un énfasis en la formación de psicólogos escolares. Los presupuestos teóricos que basaron esa formación se fundamentan en la Psicología Escolar Crítica y en la Psicología Histórico Cultural. Se presentarán experiencias de prácticas junto a la psicóloga escolar del sistema de enseñanza pública del Distrito Federal que desarrolla una actuación institucional con el foco en la potenciación colectiva y en la búsqueda del éxito escolar. Las acciones de prácticas buscaron fortalecer el papel del psicólogo escolar en la mediación del desarrollo humano y de transformaciones socio-políticas existentes en los contextos de la educación pública en el país. Se espera, con ese trabajo, contribuir a la ampliación de las reflexiones acerca del compromiso con la formación en psicología escolar en la graduación por medio de una crítica articulación teoría-práctica, contextualizada por la práxis cotidiana de psicólogos que son escolares y no sólo están en la escuela.O tema da formação inicial em Psicologia vem motivando vastos estudos e publicações na área da Psicologia Escolar, especialmente visando maior criticidade à formação e consequente atuação. Este artigo tem como objetivo apresentar ações de supervisão de estágio profissional com ênfase à formação de psicólogos escolares. Os pressupostos teóricos que embasaram essa formação fundamentam-se na Psicologia Escolar Crítica e na Psicologia histórico-cultural. Serão relatadas experiências de estágio junto a uma psicóloga escolar que trabalha no sistema de ensino público do Distrito Federal e que desenvolve uma atuação institucional com o foco no empoderamento coletivo e no sucesso escolar. As ações de estágio buscaram fortalecer o papel do(a) psicólogo(a) escolar na mediação do desenvolvimento humano e de transformações sócio-políticas prementes nos contextos da educação pública no país. Espera-se com este trabalho contribuir para a ampliação das reflexões acerca do compromisso com a formação em Psicologia Escolar na graduação por meio de uma crítica articulação teoria-prática, contextualizada pela práxis cotidiana de psicólogos(as) que são escolares, e não somente estão na escola