Luciana Andrade

DISTRIBUTION OF HNA AND LNA BACTERIAL GROUPS IN THE SOUTHWEST ATLANTIC OCEAN

Um estudo do bacterioplâncton foi realizado numa area extensa do Oceano Atlântico Sudoeste entre 13 e 25oS e 28 e 42oW. As amostras foram coletadas em 108 estacoes oceanograficas a 20 m de profundidade. A abundância bacteriana foi determinada por citometria de fluxo apos coloracao dos acidos nucleicos com Syto13. Dois grupos de bacterias foram enumerados e distinguidos: bacterias com alto conteudo de acidos nucleicos (HNA) e bacterias com baixo conteudo de acidos nucleicos (LNA). O numero de bacterias variou de 0,37 a 5,53 105 celulas mL-1. As celulas HNA representaram de 15 a 70% da abundância total enquanto as celulas LNA representaram de 30 a 85%. A producao bacteriana foi determinada por incorporacao de leucina tritiada e variou de 2,7 a 171,07 ng C L-1 h-1. A correlacao entre abundância e producao bacterianas nao foi significativa. Entretanto uma analise multivariada realizada entre abundância, producao, clorofila a e outros dados oceanograficos revelou que a distribuicao dos dois grupos em diferentes provincias oceânicas pode ser atribuida a disponibilidade de nutrientes. As bacterias HNA foram responsaveis pelo maior percentual de celulas na area ao norte de 19oS e estiveram relacionadas as aguas quentes e aos nutrientes de origem pluvial. As bacterias LNA foram dominantes ao sul dessa latitude e estiveram relacionadas a disponibilidade de nitrato cujos valores foram mais altos nessa regiao.

Zinc detoxification by a cyanobacterium from a metal contaminated bay in Brazil

We describe here the trapping of zinc in polyphosphate granules of the cyanobacterium Synechocystis aquatilis NPBS-3. Cells were cultured in 25 µM of zinc chloride and prepared for electron microscopy and energy-dispersive X-ray analysis. Some ultrastructural features were changed by zinc exposure, the increase of glycogen granules number being the main change. The polyphosphate granules contained phosphorus, sulphur, calcium, iron and zinc. The trapping of zinc in polyphosphate granules seemed to be an effective way of detoxifying the metal and surviving in the bay. As a non-specific mechanism, these polyphosphate granules could also be effective in trapping other metals in excess.

Bacterial production in Guanabara Bay (Rio de Janeiro, Brazil) evaluated by ³H-leucine incorporation

The aim of this work was to evaluate the necessary 3H-leucine concentration to estimate bacterial production in Guanabara Bay through saturation curves. A second aim was to collect preliminary data of bacterial production in two distinct sites corresponding to different water qualities: Urca inlet and Governador Island. Saturation curves were made with water samples taken at the main circulation channel of the bay, Paqueta Island, and the two sites mentioned before. The 3H-leucine curves showed similar pattern for all studied areas, indicating the ideal isotope concentration to be 10 nM. Bacterial biomass production ranged from 0.40 to 4.53 µgC L-1 h-1 in Urca and from 3.86 to 73.72 µgC L-1 h-1 in Governador Island indicating the relationship between nutrients and organic matter supply and bacterial productivity. This work is an important reference for studies on trophodynamics, biogeochemical cycles and modelling in Guanabara Bay.

Characterization of Crystalline Hydroxyapatite Thin Coatings for Biomedical Applications

Crystalline hydroxyapatite thin coatings have been prepared using a novel opposing RF magnetron sputtering approach at room temperature. X-ray diffraction (XRD) analysis shows that all the principal peaks are attributable to HA, and the as-deposited HA coatings are made up of crystallites in the size range of 50-100nm. Fourier transform infrared spectroscopy (FTIR) studies reveal the existence of phosphate, carbonate and hydroxyl groups, suggesting that HA coatings are carbonated. Finally, in vitro cell culture experiments have demonstrated that murine osteoblast cells attach and grow well on the as-sputtered coatings. These results encourage further studies of hydroxyapatite thin coatings prepared by the opposing RF magnetron sputtering approach as a promising candidate for next-generation bioimplant materials.

In Vitro Evaluation of Porous Biphasic Scaffolds

In the present study, two methods for the production of three-dimensional scaffolds made of bioactive ceramics are presented. Depending on the method, the final product can be composed by pure hydroxyapatite or biphasic: hydroxiapatite + tricalcium phosphate. Bioactivity tests showed that all scaffolds are bioactive. Preliminary studies with adipose stem cells indicated biocompatibility of both scaffolds.

VIRIOPLÂNCTON E BACTERIOPLÂNCTON: DESCRITORES ESPACIAIS E TEMPORAIS

RESUMO A estrutura e consequente funcao da cadeia alimentar das aguas oceânicas profundas e assunto de crescente interesse em oceanografia. Os perfis verticais (1-2.300 m) do bacterioplâncton e virioplâncton no Oceano Atlântico Sudoeste obtidos no ano de 2009 foram analisados e descritos nesse estudo. O numero de virus, bacterias totais, HNA e LNA foi determinado por meio de citometria em fluxo. Normalmente, as bacterias com baixo teor de acidos nucleicos (LNA) dominaram a camada eufotica, correspondendo a mais de 80-90% da abundância bacteriana total. O numero total de bacterias diminuiu cerca de uma ordem de grandeza com o aumento da profundidade. Apesar disso, a proporcao de bacterias com alto teor de acidos nucleicos (HNA) aumentou ao longo do perfil vertical. Nas maiores profundidades, as celulas HNA tenderam a dominar a abundância de bacterias heterotroficas, representando cerca de 80-90% do numero total. Nas maiores profundidades, as condicoes ambientais sao mais favoraveis as bacterias do que aos seus competidores e predadores, uma vez que existe uma grande disponibilidade de nutrientes, algumas fontes de carbono que podem ser rapidamente captadas, e uma menor pressao de predacao. A interacao dos fatores mencionados anteriormente gera melhores condicoes para o desenvolvimento de determinadas populacoes bacterianas, favorecendo o crescimento e a dominância de celulas HNA ao inves de LNA. As celulas HNA, mais numerosas nas aguas profundas, sao reconhecidas como mais versateis e, portanto, responsaveis por uma parcela significativa do metabolismo batipelagico. Tais celulas sao de grande importância na alca microbiana da camada afotica, e seu estudo contribui para o maior entendimento da ecologia microbiana em aguas profundas. Nao observamos variacao sazonal para o bacterioplâncton, entretanto o virioplâncton foi significativamente mais abundante no verao, mostrando que a comunidade microbiana foi controlada pela infeccao viral.

PVT Properties of Live Crude Oils from Upstream Production Platforms

The physical and compositional properties of live crude oils strongly affect the strategy of transportation of oil and gas from reservoirs to the stock tank and their storage. The relevant PVT properties of live crude oils like solution gas-oil ratio and oil formation volume factor should be measured preferably in laboratory for different pressures at the process or reservoir temperature. The sampling and PVT analysis include time consuming or expensive procedures and the data obtained are correlated for interpolation or estimation of properties. These properties vary considerably for different classes of crude oils. We obtain experimental data of crude oils properties from the PVT analysis of primary high-pressure separator samples of 260 live paraffinic-naphthenic crude oils from forty-four Brazilian oil wells. The solution gas-oil ratio and oil formation volume factor were obtained within experimental uncertainties of 5.79% and 1.00%, respectively. We have compared the results with the estimates of several cubic equations of state as well as with widely used literature correlations. The best equation of state estimate solution gas-oil ratio with average absolute percent relative error (AARE) of 10.36%, better than the empirical correlations in the literature using measured temperature, pressure and composition, the empirical correlation for solution gas-oil ratio with parameters estimated from the experimental data shows an AARE of 10.77%. The equations of state and literature correlations estimate the oil formation volume factor with an AARE about 2%, which is lower than the needed accuracy. The measured oil formation volume factors are correlated with an average absolute percent relative error of 1.18%, with a proposed correlation using readily measured liquid densities and solution gas-oil ratio. We can estimate the solution gas-oil ratio by Peng-Robinson equation of state and oil formation volume factor by proposed correlation to the needed accuracy for live paraffinic-naphthenic crude oils under separator conditions from composition, temperature and densities of gas and oil.