Unique Flexibility in Energy Metabolism Allows Mycobacteria to Combat Starvation and Hypoxia

Mycobacteria are a group of obligate aerobes that require oxygen for growth, but paradoxically have the ability to survive and metabolize under hypoxia. The mechanisms responsible for this metabolic plasticity are unknown. Here, we report on the adaptation of Mycobacterium smegmatis to slow growth rate and hypoxia using carbon-limited continuous culture. When M. smegmatis is switched from a 4.6 h to a 69 h doubling time at a constant oxygen saturation of 50%, the cells respond through the down regulation of respiratory chain components and the F1Fo-ATP synthase, consistent with the cells lower demand for energy at a reduced growth rate. This was paralleled by an up regulation of molecular machinery that allowed more efficient energy generation (i.e. Complex I) and the use of alternative electron donors (e.g. hydrogenases and primary dehydrogenases) to maintain the flow of reducing equivalents to the electron transport chain during conditions of severe energy limitation. A hydrogenase mutant showed a 40% reduction in growth yield highlighting the importance of this enzyme in adaptation to low energy supply. Slow growing cells at 50% oxygen saturation subjected to hypoxia (0.6% oxygen saturation) responded by switching on oxygen scavenging cytochrome bd, proton-translocating cytochrome bc1-aa3 supercomplex, another putative hydrogenase, and by substituting NAD+-dependent enzymes with ferredoxin-dependent enzymes thus highlighting a new pattern of mycobacterial adaptation to hypoxia. The expression of ferredoxins and a hydrogenase provides a potential conduit for disposing of and transferring electrons in the absence of exogenous electron acceptors. The use of ferredoxin-dependent enzymes would allow the cell to maintain a high carbon flux through its central carbon metabolism independent of the NAD+/NADH ratio. These data demonstrate the remarkable metabolic plasticity of the mycobacterial cell and provide a new framework for understanding their ability to survive under low energy conditions and hypoxia

Rhodolith Beds Are Major CaCO3 Bio-Factories in the Tropical South West Atlantic

Rhodoliths are nodules of non-geniculate coralline algae that occur in shallow waters (<150 m depth) subjected to episodic disturbance. Rhodolith beds stand with kelp beds, seagrass meadows, and coralline algal reefs as one of the world's four largest macrophyte-dominated benthic communities. Geographic distribution of rhodolith beds is discontinuous, with large concentrations off Japan, Australia and the Gulf of California, as well as in the Mediterranean, North Atlantic, eastern Caribbean and Brazil. Although there are major gaps in terms of seabed habitat mapping, the largest rhodolith beds are purported to occur off Brazil, where these communities are recorded across a wide latitudinal range (2°N - 27°S). To quantify their extent, we carried out an inter-reefal seabed habitat survey on the Abrolhos Shelf (16°50′ - 19°45′S) off eastern Brazil, and confirmed the most expansive and contiguous rhodolith bed in the world, covering about 20,900 km2. Distribution, extent, composition and structure of this bed were assessed with side scan sonar, remotely operated vehicles, and SCUBA. The mean rate of CaCO3 production was estimated from in situ growth assays at 1.07 kg m−2 yr−1, with a total production rate of 0.025 Gt yr−1, comparable to those of the world's largest biogenic CaCO3 deposits. These gigantic rhodolith beds, of areal extent equivalent to the Great Barrier Reef, Australia, are a critical, yet poorly understood component of the tropical South Atlantic Ocean. Based on the relatively high vulnerability of coralline algae to ocean acidification, these beds are likely to experience a profound restructuring in the coming decades

Intervenção multiprofissional melhora a aptidão física relacionada à saúde de adolescentes com maior efeito sobre as meninas em comparação aos meninos

Resumo Este estudo teve como objetivo verificar as diferenças entre as respostas de meninos e meninas a um programa multiprofissional de tratamento da obesidade sobre a aptidão física relacionada à saúde. Fizeram parte do estudo 163 adolescentes com excesso de massa corporal e idade entre 10 e 18 anos. Foram avaliados parâmetros antropométricos, composição corporal, flexibilidade, força e resistência abdominal e aptidão cardiorrespiratória antes e após 16 semanas de intervenção multiprofissional. A intervenção multiprofissional contou com a participação de profissionais de educação física, nutrição, psicologia e pediatria e teve como foco principal o incentivo a mudanças nos hábitos alimentares e de atividade física que pudessem promover alterações positivas nos parâmetros analisados. A intervenção teve frequência semanal de três sessões, sendo uma hora de intervenções teóricas com os profissionais de educação física, nutrição e psicologia e a outra hora destinada à prática regular de exercícios físicos, com predominância de exercícios físicos resistidos, aeróbios e prática de basquetebol. Após a intervenção tanto as meninas quanto os meninos apresentaram melhoras significativas nas variáveis IMC, circunferência de cintura e quadril, massa gorda relativa e absoluta, massa magra, flexibilidade, força/resistência abdominal e aptidão cardiorrespiratória, porém com resultados mais expressivos para as meninas sobre a circunferência de cintura, gordura corporal (kg), VO2max e força/resistência abdominal