Environmental influences on akinete germination and development in Nodularia spumigena (Cyanobacteriaceae), isolated from the Gippsland Lakes, Victoria, Australia

This study was carried out to investigate the genesis of N. spumigena blooms by specifically studying the effects of environmental variables (salinity, nitrogen, phosphorus and light) on the germination of N. spumigena akinetes. Optimal conditions for maximum germination and germling growth were determined by exposing akinetes to a range of salinities and nutrient (nitrogen and phosphorus) concentrations under two different irradiances. At pre-determined time periods, treatments were sampled and the percent germination and length of germlings assessed. The results indicated that akinete germination and germling growth were optimal at salinities from 5 to 25 and significantly reduced outside this range. A positive correlation in germination was observed with increasing nutrient (phosphorus and nitrate) concentration. Similarly, germling growth increased with increasing concentrations of both nutrients. Irradiance significantly influenced both germination and growth during salinity experiments, whereas in nutrient addition experiments, irradiance had no effect on germination; however, growth was significantly influenced during phosphorus addition experiments. Consequently, salinity and light appeared to be most critical in the germination process for N. spumigena akinetes, with phosphorus most important for germling growth. The study showed that N. spumigena may be able to germinate under environmental conditions outside its optimal range, but the growth of the germling is significantly reduced, which in turn suggests that its ability to form a bloom outside its optimal environmental conditions would also be greatly reduced.

Physiological metal uptake by Nostoc punctiforme

Trace metals are required for many cellular processes. The acquisition of trace elements from the environment includes a rapid adsorption of metals to the cell surface, followed by a slower internalization. We investigated the uptake of the trace elements Co²⁺, Cu²⁺, Mn²⁺, Ni²⁺, and Zn²⁺ and the non-essential divalent cation Cd²⁺ in the cyanobacterium Nostoc punctiforme. For each metal, a dose response study based on cell viability showed that the highest non-toxic concentrations were: 0.5 μM Cd²⁺, 2 μM Co²⁺, 0.5 μM Cu²⁺, 500 μM Mn²⁺, 1 μM Ni²⁺, and 18 μM Zn²⁺. Cells exposed to these non-toxic concentrations with combinations of Zn²⁺ and Cd²⁺, Zn²⁺ and Co²⁺, Zn²⁺ and Cu²⁺ or Zn²⁺ and Ni²⁺, had reduced growth in comparison to controls. Cells exposed to metal combinations with the addition of 500 μM Mn²⁺ showed similar growth compared to the untreated controls. Metal levels were measured after one and 72 h for whole cells and absorbed (EDTA-resistant) fractions and used to calculate differential uptake rates for each metal. The differences in binding and internalisation between different metals indicate different uptake processes exist for each metal. For each metal, competitive uptake experiments using ⁶⁵Zn showed that after 72 h of exposure Zn²⁺ uptake was reduced by most metals particularly 0.5 μM Cd²⁺, while 2 μM Co²⁺ increased Zn²⁺ uptake. This study demonstrates that N. punctiforme discriminates between different metals and favourably substitutes their uptake to avoid the toxic effects of particular metals.

Unsafe abortion as a birth control method: maternal mortality risks among unmarried Cambodian migrant women on the Thai-Cambodia border

Reproductive health research and policies in Cambodia focus on safe motherhood programs particularly for married women, ignoring comprehensive fertility regulation programs for unmarried migrant women of reproductive age. Maternal mortality risks arising due to unsafe abortion methods practiced by unmarried Cambodian women, across the Thai-Cambodia border, can be considered as a public health emergency. Since Thailand has restrictive abortion laws, Cambodian migrant women who have irregular migration status in Thailand experimented with unsafe abortion methods that allowed them to terminate their pregnancies surreptitiously. Unmarried migrant women choose abortion as a preferred birth control method seeking repeat “unsafe” abortions instead of preventing conception. Drawing on the data collected through surveys, in-depth interviews, and document analysis in Chup Commune (pseudonym), Phnom Penh, and Bangkok, the authors describe the public health dimensions of maternal mortality risks faced by unmarried Cambodian migrant women due to various unsafe abortion methods employed as birth control methods.

Functional characterization of the twin ZIP/SLC39 metal transporters, NpunF3111 and NpunF2202 in Nostoc punctiforme

The ZIP family of metal transporters is involved in the transport of Zn2+ and other metal cations from the extracellular environment and/or organelles into the cytoplasm of prokaryotes, eukaryotes and archaeotes. In the present study, we identified twin ZIP transporters, Zip11 (Npun_F3111) and Zip63 (Npun_F2202) encoded within the genome of the filamentous cyanobacterium, Nostoc punctiforme PCC73120. Sequence-based analyses and structural predictions confirmed that these cyanobacterial transporters belong to the SLC39 subfamily of metal transporters. Quantitative real-time (QRT)-PCR analyses suggested that the enzymes encoded by zip11 and zip63 have a broad allocrite range that includes zinc as well as cadmium, cobalt, copper, manganese and nickel. Inactivation of either zip11 or zip63 via insertional mutagenesis in N. punctiforme resulted in reduced expression of both genes, highlighting a possible co-regulation mechanism. Uptake experiments using 65Zn demonstrated that both zip mutants had diminished zinc uptake capacity, with the deletion of zip11 resulting in the greatest overall reduction in 65Zn uptake. Over-expression of Zip11 and Zip63 in an E. coli mutant strain (ZupT736::kan) restored divalent metal cation uptake, providing further evidence that these transporters are involved in Zn uptake in N. punctiforme. Our findings show the functional role of these twin metal uptake transporters in N. punctiforme, which are independently expressed in the presence of an array of metals. Both Zip11 and Zip63 are required for the maintenance of homeostatic levels of intracellular zinc N. punctiforme, although Zip11 appears to be the primary zinc transporter in this cyanobacterium, both ZIP's may be part of a larger metal uptake system with shared regulatory elements.

Molecular and cellular characterisation of the zinc uptake (Znu) system of Nostoc punctiforme

Metal homoeostasis in cyanobacteria is based on uptake and export systems that are controlled by their own regulators. This study characterises the zinc uptake (Znu) system in Nostoc punctiforme. The system was found to comprise of three subunits in an ACB operon: a Zn2+-binding protein (ZnuA18), a transmembrane domain (ZnuB) and an ATPase (ZnuC). These proteins are encoded within the znu operon regulated by a zinc uptake transcription repressor (Zur). Interestingly, a second Zn2+-binding protein (ZnuA08) was also identified at a distal genomic location. Interactions between components of the ZnuACB system were investigated using knockouts of the individual genes. The znuA08-, znuA18-, znuB- and znuC- mutants displayed overall reduced znuACB transcript levels, suggesting that all system components are required for normal expression of znu genes. Zinc uptake assays in the Zn2+-binding protein mutant strains showed that the disruption of znuA18 had a greater negative effect on zinc uptake than disruption of znuA08. Complementation studies in Escherichia coli indicated that both znuA08 and znuA18 were able to restore zinc uptake in a znuA- mutant, with znuA18 permitting the highest zinc uptake rate. The N. punctiforme zur was also able to complement the E. coli zur- mutant.

Long-term changes in abundance and distribution of microzooplankton in the NE Atlantic and North Sea

Long-term changes in mesozooplankton and phytoplankton populations have been well documented in the North Atlantic region, whereas data for microzooplankton are scarce. This neglected component of the plankton is a vital link in marine food-webs, grazing on smaller flagellates and cyanobacteria and in turn providing food for the larger mesozooplankton. We use the latest tintinnid (Ciliophora, Protista) data from the Continuous Plankton Recorder (CPR) survey in the NE Atlantic and North Sea to examine the phenology, distribution and abundance of this important group of ciliates. Presence/absence data came from 167 122 CPR samples collected between 1960 and 2009 and abundance data from 49 662 samples collected between 1996 and 2009. In the North Atlantic the genus Dictyocysta spp. dominated and Parafavella gigantea showed an increase in abundance around Iceland and Greenland. In the North Sea higher densities of Tintinnopsis spp., Favella serrata and Ptychocylis spp. were found. The presence of tintinnids in CPR samples collected in the North Atlantic has increased over the last 50 years and the seasonal window of high abundance has lengthened. Conversely in the North Sea there has been an overall reduction in abundance. We discuss possible drivers for these long-term changes and point the way forward to more holistic studies that examine how ecosystems, rather than just selected taxa, are responding to climate change.

Inquisition of Microcystis aeruginosa and Synechocystis nanowires: characterization and modelling

Identification of extracellular conductive pilus-like structures (PLS) i.e. microbial nanowires has spurred great interest among scientists due to their potential applications in the fields of biogeochemistry, bioelectronics, bioremediation etc. Using conductive atomic force microscopy, we identified microbial nanowires in Microcystis aeruginosa PCC 7806 which is an aerobic, photosynthetic microorganism. We also confirmed the earlier finding that Synechocystis sp. PCC 6803 produces microbial nanowires. In contrast to the use of highly instrumented continuous flow reactors for Synechocystis reported earlier, we identified simple and optimum culture conditions which allow increased production of nanowires in both test cyanobacteria. Production of these nanowires in Synechocystis and Microcystis were found to be sensitive to the availability of carbon source and light intensity. These structures seem to be proteinaceous in nature and their diameter was found to be 4.5-7 and 8.5-11 nm in Synechocystis and M. aeruginosa, respectively. Characterization of Synechocystis nanowires by transmission electron microscopy and biochemical techniques confirmed that they are type IV pili (TFP) while nanowires in M. aeruginosa were found to be similar to an unnamed protein (GenBank : CAO90693.1). Modelling studies of the Synechocystis TFP subunit i.e. PilA1 indicated that strategically placed aromatic amino acids may be involved in electron transfer through these nanowires. This study identifies PLS from Microcystis which can act as nanowires and supports the earlier hypothesis that microbial nanowires are widespread in nature and play diverse roles.

Characterization of two cation diffusion facilitators NpunF0707 and NpunF1794 in Nostoc punctiforme

AIMS: To characterize genes involved in maintaining homeostatic levels of zinc in the cyanobacterium Nostoc punctiforme. METHODS AND RESULTS: Metal efflux transporters play a central role in maintaining homeostatic levels of trace elements such as zinc. Sequence analyses of the N. punctiforme genome identified two potential cation diffusion facilitator (CDF) metal efflux transporters, Npun_F0707 (Cdf31) and Npun_F1794 (Cdf33). Deletion of either Cdf31or Cdf33 resulted in increased zinc retention over 3 h. Interestingly, Cdf31(-) and Cdf33(-) mutants showed no change in sensitivity to zinc exposure in comparison with the wild type, suggesting some compensatory capacity for the loss of each other. Using qRT-PCR, a possible interaction was observed between the two cdf's, where the Cdf31(-) mutant had a more profound effect on cdf33 expression than Cdf33(-) did on cdf31. Over-expression of Cdf31 and Cdf33 in ZntA(-) - and ZitB(-) -deficient Escherichia coli revealed function similarities between the ZntA and ZitB of E. coli and the cyanobacterial transporters. CONCLUSIONS: The data presented shed light on the function of two important transporters that regulate zinc homeostasis in N. punctiforme. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows for the first time the functional characterization of two cyanobacterial zinc efflux proteins belonging to the CDF family.

The ZntA-like NpunR4017 plays a key role in maintaining homeostatic levels of zinc in Nostoc punctiforme

Analysis of cellular response to zinc exposure provides insights into how organisms maintain homeostatic levels of zinc that are essential, while avoiding potentially toxic cytosolic levels. Using the cyanobacterium Nostoc punctiforme as a model, qRT-PCR analyses established a profile of the changes in relative mRNA levels of the ZntA-like zinc efflux transporter NpunR4017 in response to extracellular zinc. In cells treated with 18 μM of zinc for 1 h, NpunR4017 mRNA levels increased by up to 1300 % above basal levels. The accumulation and retention of radiolabelled (65)Zn by NpunR4107-deficient and overexpressing strains were compared to wild-type levels. Disruption of NpunR4017 resulted in a significant increase in zinc accumulation up to 24 % greater than the wild type, while cells overexpressing NpunR4107 accumulated 22 % less than the wild type. Accumulation of (65)Zn in ZntA(-) Escherichia coli overexpressing NpunR4017 was reduced by up to 21 %, indicating the capacity for NpunR4017 to compensate for the loss of ZntA. These findings establish the newly identified NpunR4017 as a zinc efflux transporter and a key transporter for maintaining zinc homeostasis in N. punctiforme.

Estudo da influência de manejos pós-colheita na incidência de fungos e micotoxinas no arroz (Oryza sativa L.)

Cerca de 15% da safra de arroz é perdida anualmente, principalmente em práticas inadequadas de pós-colheita. Nesse contexto, a avaliação de técnicas de secagem e armazenamento é necessária em função das perdas quali e quantitativas de grãos, resultantes do desenvolvimento de fungos. O objetivo desse trabalho foi analisar a contaminação fúngica e por micotoxinas do arroz submetido aos sistemas de secagem intermitente e estacionário, com armazenamento em sacaria e em silo-secador, avaliando o comportamento das principais variáveis de influência no processo. O trabalho foi realizado entre os meses de maio de 2003 a maio de 2004. As amostras de arroz com casca foram coletadas a cada dois meses, em duplicatas. Foram, ainda, analisadas amostras de arroz branco polido e parboilizado de ambos sistemas. O número de colônias de bolores e leveduras foi determinado e a capacidade produtora de micotoxinas dos isolados do gênero Aspergillus foi investigada. A detecção de aflatoxinas, ocratoxina A, zearalenona e citrinina foi realizada por cromatografia em camada delgada. Os grãos secados no sistema estacionário apresentaram maior contagem de colônias fúngicas. Enquanto no sistema intermitente, a contaminação foi mais uniforme ao longo do armazenamento. Predominaram representantes do gênero Penicillium nos dois sistemas, principalmente P. commune e P. islandicum. Entre os isolados do gênero Aspergillus, destacou-se A. flavus. Foram encontrados 7 (13, 20%) isolados de A.flavus produtores de aflatoxina B1, mas não foram detectadas micotoxinas nas amostras. A umidade dos grãos afetou significativamente a contaminação fúngica no manejo intermitente e no terço superior (altura 2) do silo-secador. A temperatura no interior do silo influenciou a contaminação no terço inferior (altura 1).

Os discursos preventivos sobre o uso de drogas e as potencialidades dos educadores na prevenção primária: relato de uma experiência

Este estudo objetiva definir as potencialidades dos educadores na prevenção primária do uso e do abuso de drogas, llcitas e ilicitas. Na primeira parte deste texto, foram analisados alguns manuais destinados a prevençao nas Escolas do nosso pais, selecionados e classificados de acordo com os diferentes discursos, neles contidos, quanto ao uso de drogas e quanto ã atuação dos educadores na prevenção primária. Na segunda parte, procedeu-se ao relato de uma experiência particular de prevençao primária, desenvolvida num municlpio do estado do Rio de Janeiro, durante o ano de 1988, realizada com educadores da região. Durante esta experiência, procurou-se construir uma visão critica sobre o uso de drogas, sobre os diferentes nlveis de consumo e sobre o momento sóciocultural no qual se dá esta prática. Do ponto de vista metodológico, bu~ cou-se apoio na pedagogia psicanalitica, resgatando experiências quotidianas na construção de um saber coletivo, definido como a prevenção que aqueles educadores desejavam desenvolver. Utilizou-se, tambem, tecnicas de mo bilização e de integração, atraves das quais, processos de projeção e introjeção puderam resultar numa elaboração interna das questões relativas ao uso e abuso de drogas. A análise dos manuais e da experiência particular de prevenção primária relatada, apontou alguns caminhos: propostas preventivas autoritárias devem ser definitivamente superadas; propostas preventivas que privilegiem a escuta da demanda de orientação e de ajuda, por parte dos alunos usuários de drogas, que admitam a discussão sobre a estrutura geradora do consumo de drogas, que incorporem a necessidade de prazer e se liberem das imposições do poder constituido, têm possibilidades de contribuir para a diminuição dos problemas decorrentes do abuso de drogas; as práticas dos educadores na prevenção primária do uso e do abuso de drogas terão mais chances na medida em que houver um processo de "desintoxicação" da própria sociedade.

O sistema educacional e uma prática viabilizada em escolas de 1. grau

O presente trabalho resulta de questionamentos sucessivos que, durante o desempenho da função de professora, foram-se avolumando. Entre os problemas destacam-se o da evasão e da repetência, responsáveis pela exclusão de um contingente elevado de alunos do sistema escolar. Esta problemática converteu-se em ob jeto de estudo desta dissertação. O estudo realizado baseou-se na reflexão sobre a posição teórica dos seguintes autores: Gramsci, Bourdieu, Passeron, Baudelot e Establet. A razão da escolha destes teóricos prende-se ao fato de que, apesar de diferirem em muitos aspectos, aproximam-se em outros. Assim, entre os pontos que convergem, está o fato de remeterem seus estudos a um tipo de sociedade, cujas relações entre as classes sociais existentes, são relações de oposição. Foi utilizada a metodologia dialética para tratar os acontecimentos sociais, buscando explicitá-los não como se apresentam aos homens à primeira vista, em seu aparente, mas através de uma movimentação profunda que se oculta sob a movimentação superficial, onde as partes se relacionam internamente, estando em conexão entre si e com o todo. A pesquisa realizou-se em duas etapas: a primeira constou de leitura critica de vários documentos elaborados pela Secretaria de Educação com vistas a estudar a normatividade que deles decorre e como norteiam as práticas educativas; a segunda etapa desenvolveu-se em duas escolas públicas da rede estadual na cidade de são Luís, com vistas a analisar como essas práticas são viabilizadas nas escolas. Para tanto, foram utilizadas técnicas de observação participante e entrevistas, a fim de se estudar o problema numa abordagem qualitativa. Foram aplicados questionários aos seguintes profissionai s: ao corpo docente, com o objetivo de verificar como as práticas educativas se desenvolvem na sala de aula; às diretoras, com vistas a detectar como as escolas se relacionam com a instância superior à qual estão ligadas; às supervisoras, com o objetivo de verificar como desenvolvem seu trabalho junto às escolas e aos pais dos alunos, com o intuito de inferir suas espectativas, ou seja, o que eles esperam que a escola propicie a seus filhos. Conclui-se que o processo educacional desenvolvido nessas escolas nao se realiza no vazio, e nem isoladamente. Sua ação é um reflexo da realidade social mais ampla, razão por que é determinada pelo contexto sócio-político do qual faz parte. A inexistência de uma proposta de currículo pleno , de uma avaliação em nível de realidade regional e de uma reflexão crítica sobre a pedagogia aplicada, faz da lnstituição escolar uma estrutura de poder que está a serviço, sobretudo , de determinados interesses. Nesse contexto, as igualdades de na legislação entrechocam-se com as oportunidades desigualdades sócio-econômicas e culturais da maioria desses alunos , resultando num ensino anti-democrático. As sugestões propostas visam minorar a situação de precariedade com que se desenvolve o processo educacional nas escolas públicas da cidade de são Luís , ligadas a Secretaria de Educação do Estado do Maranhão.