Excreção de matéria orgânica dissolvida por populações fitoplanctônicas marinhas em bioensaios com nutrientes

Measurements of excreted dissolved organic matter (DOM) were carried out twice (in simmer and winter) using natural phytoplankton populations from "Enseada do Flamengo" (Lot. 23° 30'S-Long. 045°069'W) and enriched artificially with nutrients. The bioassays were carried out inoculating samples of an integral sea water in ten liters flasks, incubated "in situ". Measures were taken in populations growing in: integral " f " media, "f" - N, "f" - P, "f" - (H + P), "f" - (Vit. + Metal traces), and in a control without enrichment. The absolute amount of excreted DOM generally followed the quantity of total carbon assimilated. In the meantime, with the populations with nitrogen deficiency occurred an increase of relatives rates of excretion, not only due to the total carbon assimilation diminution, but effectively also to the absolute increase of the quantity of excreted DOM.Foram efetuadas várias medidas de excreção de matéria orgânica dissolvida (MOD), utilizando-se populações naturais de fitoplâncton, provenientes da Enseada do Flamengo - litoral Norte do Estado de São Paulo - e enriquecidas artificialmente com nutrientes. A quantidade absoluta da MOD excretada, de um modo geral, acompanhou a quantidade de carbono total assimilado. Entretanto, nas populações com deficiência de nitrogênio, ocorreu um aumento das taxas relativas de excreção, não só devido à diminuição da assimilação total de carbono, mas, efetivamente, tambem ao aumento da quantidade absoluta de MOD excretada

Regional factors as major drivers for microbial community turnover in tropical cascading reservoirs

The turnover of microbial communities across space is dictated by local and regional factors. Locally, selection shapes community assembly through biological interactions between organisms and the environment, while regional factors influence microbial dispersion patterns. Methods used to disentangle the effects of local and regional factors typically do not aim to identify ecological processes underlying the turnover. In this paper, we identified and quantified these processes for three operational microbial subcommunities (cyanobacteria, particle-attached, and free-living bacteria) from a tropical cascade of freshwater reservoirs with decreasing productivity, over two markedly different dry and rainy seasons. We hypothesized that during the dry season communities would mainly be controlled by selection shaped by the higher environmental heterogeneity that results from low hydrological flow and connectivity between reservoirs. We expected highly similar communities shaped by dispersal and a more homogenized environment during the rainy season, enhanced by increased flow rates. Even if metacommunities were largely controlled by regional events in both periods, the selection had more influence on free-living communities during the dry period, possibly related to elevated dissolved organic carbon concentration, while drift as a purely stochastic factor, had more influence on cyanobacterial communities. Each subcommunity had distinct patterns of turnover along the cascade related to diversity (Cyanobacteria), lifestyle and size (Free-living), and spatial dynamics (particle-attached)

Carotenogenesis in Haematococcus pluvialis cells induced by light and nutrient stresses

O objetivo deste trabalho foi avaliar as respostas das células de Haematococcus pluvialis ao processo de indução à carotenogênese, sob estresse luminoso e nutricional. As células foram aclimatadas durante 15 dias em meio WC, com aeração com ar atmosférico sintético filtrado e fluxo de 100 mL min‑1, intensidade luminosa de 50 μmol fótons m‑2 s‑1 , fotoperíodo de 12 horas e temperatura de 23°C. Foram comparados dois tratamentos: cultivo nas condições descritas, mas com aumento da intensidade luminosa para 350 μmol fótons m‑2 s‑1; e cultivo nas mesmas condições do tratamento anterior, mas com aeração contendo 4% de CO2. Os tratamentos foram conduzidos em triplicata, durante dez dias. Com a adição de CO2 e o incremento da iluminação, observou-se aumento da razãocarotenoides/clorofila e da biomassa celular. As células cessaram a divisão no segundo dia de estresse, quando o nitrato se tornou limitante, e aumentaram significativamente seu biovolume. A excreção de carbono orgânico e a concentração de astaxantina aumentam em resposta à adição de CO2. O estresse por intensidade luminosa, aliado à adição de CO2, otimiza a carotenogênese em H. pluvialis e aumenta a produção de astaxantina.The objective of this work was to evaluate the responses of Haematococcus pluvialis cells to the carotenogenesis induction process, under light and nutrition stress. Cells were acclimated during 15 days in WC medium, with aeration with synthetic, filtered atmospheric air and flow rate of 100 mL min‑1, light intensity of 50 μmol photons m‑2 s‑1, photoperiod of 12 hours, and temperature of 23°C. The following two treatments were compared: cultivation under the described conditions, but with increase of light intensity up to 350 μmol photons m‑2 s‑1; and cultivation under the same conditions as the previous treatment, but with aeration containing 4% CO2. The treatments were done in triplicate, during ten days. With the addition of CO2 and the increment in lighting, an increase was observed in the carotenoids/chlorophyll ratio and cell biomass. Cells stopped dividing on the second day of stress, when nitrate became limiting, and significantly increased their biovolume. The excretion of organic carbon and the concentration of astaxanthin increase in response to the addition of CO2. Stress by light intensity combined with CO2 addition optimizes carotenogenesis in H. pluvialis and increases astaxanthin production

Polymeric and free sugars released by three phytoplanktonic species from a freshwater tropical eutrophic reservoir

Several studies have focused on the release of carbohydrates by phytoplankton because of the ecological significance of such compounds. This process increases the supply of carbon to the heterotrophic community, enhancing the phytoplankton/bacteria associations. In this article, we report investigations on the carbohydrate release, both polymeric and free sugars, in axenic batch cultures of three tropical freshwater phytoplanktonic species from different taxonomic positions: Cryptomonas tetrapyrenoidosa (Cryptophyceae), Staurastrum orbiculare (Zygnematophyceae) and Thalassiosira sp. (Bacillariophyceae). The total carbohydrate release rate was increased in the stationary growth phase in all the species under study. Most of the carbohydrates released by the three species were present in the polymeric form, although both polymeric and free carbohydrates could supply carbon enough to support bacterioplanktonic populations, according to rates of consumption found on literature. The composition of the carbohydrates differed significantly from one species to another, indicating that carbohydrate release might be a speciesspecific process. We also observed that the contributions of some components from polymeric sugars, such as fucose, rhamnose and arabinose increased with the advancing age of the cultures

An extracellular sulfated fucose-rich polysaccharide produced by a tropical strain of cryptomonas obovata (cryptophyceae)

A tropical strain of Cryptomonas obovata Skuja, isolated from a shallow oxbow lake, released a sulfated fucoserich polysaccharide. The polysaccharide is composed mainly of fucose (42%), N-acetyl-galactosamine (26%) and rhamnose (15%), with small quantities of glucuronic acid, mannose, galactose, xylose and glucose. Sulfate accounted for 1.7% total polysaccharide. Quantitative release was studied with cells exposed to optimal culture conditions contrasted with high irradiance and nitrate depletion. This latter set of conditions could simulate stress situati ons usually found in the place from which this strain was isolated. The monosaccharide composition of the polysaccharide was evaluated using PAD-HPLC and gas chromatography. The two irradiances tested (165 mol m−2 s−1 and 2000 mol m−2 s−1) had no significant effect on amounts of polysaccharide released by the cells. Differences were observed when the nitrate availability was varied. In the nitrate-depleted situation, extracellular polysaccharide production was 2.5 times higher than replete cells after 6 h at 165 mol m−2 s−1, and 2.25 times higher at 2000 mol m−2 s−1

Excreção de matéria orgânica dissolvida por populações fitoplanctônicas marinhas em bioensaios com nutrientes The excretion of dissolved organic matter by natural phytoplankton populations in bioassays with nutrients

Foram efetuadas várias medidas de excreção de matéria orgânica dissolvida (MOD), utilizando-se populações naturais de fitoplâncton, provenientes da Enseada do Flamengo - litoral Norte do Estado de São Paulo - e enriquecidas artificialmente com nutrientes. A quantidade absoluta da MOD excretada, de um modo geral, acompanhou a quantidade de carbono total assimilado. Entretanto, nas populações com deficiência de nitrogênio, ocorreu um aumento das taxas relativas de excreção, não só devido à diminuição da assimilação total de carbono, mas, efetivamente, tambem ao aumento da quantidade absoluta de MOD excretada.<br>Measurements of excreted dissolved organic matter (DOM) were carried out twice (in simmer and winter) using natural phytoplankton populations from "Enseada do Flamengo" (Lot. 23° 30'S-Long. 045°069'W) and enriched artificially with nutrients. The bioassays were carried out inoculating samples of an integral sea water in ten liters flasks, incubated "in situ". Measures were taken in populations growing in: integral " f " media, "f" - N, "f" - P, "f" - (H + P), "f" - (Vit. + Metal traces), and in a control without enrichment. The absolute amount of excreted DOM generally followed the quantity of total carbon assimilated. In the meantime, with the populations with nitrogen deficiency occurred an increase of relatives rates of excretion, not only due to the total carbon assimilation diminution, but effectively also to the absolute increase of the quantity of excreted DOM

Relative increase of deoxy sugars during microbial degradation of an extracellular polysaccharide released by a tropical freshwater thalassiosira sp, (bacillariophyceae)

The aim of this study was to characterize the extracellular polysaccharides (EPS) released by a freshwater Thalassiosira sp. (Bacillariophyceae) and evaluate their degradation by heterotrophic microbial populations from the same habitat of Thalassiosira sp., a tropical eutrophic reservoir. The EPS were purified by anion exchange column chromatography, the monosaccharide composition was determined by GC, and the linkages of the monosaccharides by GC-MS. The EPS is a mannose-rich heteropolysaccharide composed of two different acidic fractions. Both of these fractions are composed of mannose, rhamnose, fucose, xylose, galactose, glucose, glucuronic acid, and N-acetyl glucosamine but with different proportions. N-acetyl galactosamine occurs only in fraction 1 and galacturonic acid only in fraction 2. We monitored the concentrations of the monosaccharides in the EPS during its degradation using pulse amperometric detection in an HPLC. The decay patterns of the monosaccharides were varied and the deoxy sugars, fucose and rhamnose, were degraded at a slower rate than the other components, increasing their relative concentrations and the hydrophobic feature of the EPS. The possibility of a selective degradation, which enhances the stickiness of the EPS, promoting transparent exopolymeric particles and aggregate formation, is discussed based on the literature data

Formação de agregados em culturas de Aulacoseira granulata (Bacillariophyceae) axênicas e inoculadas com bactérias

Submitted by Ilno Conceição ([email protected]) on 2012-11-27T14:03:48Z No. of bitstreams: 1 Aggregate formation in axenic and microbial co-inoculated batch cultures of aulacoseira granulata (bacillariophycea).pdf: 96808 bytes, checksum: 92d270cadde656e55ead5128bf8141ad (MD5)Approved for entry into archive by Michele Fernanda([email protected]) on 2012-11-27T23:38:52Z (GMT) No. of bitstreams: 1 Aggregate formation in axenic and microbial co-inoculated batch cultures of aulacoseira granulata (bacillariophycea).pdf: 96808 bytes, checksum: 92d270cadde656e55ead5128bf8141ad (MD5)Made available in DSpace on 2012-11-27T23:38:52Z (GMT). No. of bitstreams: 1 Aggregate formation in axenic and microbial co-inoculated batch cultures of aulacoseira granulata (bacillariophycea).pdf: 96808 bytes, checksum: 92d270cadde656e55ead5128bf8141ad (MD5) Previous issue date: 2006Aggregate formation in axenic and microbial co-inoculated batch cultures of Aulacoseira granulata (Bacillariophyceae). Aggregate formation involving diatoms is a well-known process, especially in the marine environment. The aim of this paper was to observe natural aggregates formation in axenic and microbial co-inoculated cultures of the freshwater diatom Aulacoseira granulata. The growth of bacteria and A. granulata were also monitored, as were qualitative alterations in the composition of the extracellular polysaccharide (EPS) produced by A. granulata in both axenic and microbial co-inoculated cultures. Aggregates were naturally formed in both conditions and our results suggested that the aggregation process increased significantly in the presence of a microbial community from Barra Bonita Reservoir. A. granulata biomass formation also significantly increased along bacterial growth and the EPS composition found in the microbial co-inoculated cultures was different to that of the axenic cultures. Rhamnose proportion increased around 50 % in microbial co-inoculated cultures, probably due to bacterial activity, increasing the hydrophobic properties of the EPS. The aggregation increase in the microbial co-inoculated cultures was correlated to the enhancement of the EPS hydrophobic nature, as well as to the biomass increase of A. granulata.A formação de agregados envolvendo diatomáceas é já um processo bem conhecido, especialmente em ambientes marinhos. O objetivo deste trabalho foi observar a formação espontânea de agregados em culturas de Aulacoseira granulata axênicas e inoculadas com bactérias. O crescimento de bactérias e de A. granulata foi monitorado bem como as alterações qualitativas, causadas pela atividade bacteriana, na composição do polissacarídeo extracelular (EPS) liberado pela diatomácea em ambas as culturas. A formação de agregados ocorreu em ambas as culturas, mas os resultados sugerem que a agregação aumenta significantemente na presença de bactérias de populações oriundas do reservatório de Barra Bonita, também o local de origem da diatomácea. A biomassa de A. granulata aumentou significantemente na presença de bactérias e a composição do EPS nas culturas contaminadas foi diferente daquele das culturas axênicas. A atividade bacteriana aumentou a porcentagem do monossacarídeo Ramnose em cerca de 50 % nas culturas contaminadas, aumentando as propriedades hidrofóbicas do EPS. Assumimos que o aumento da hidrofobicidade bem como o aumento da biomassa de A. granulata nas culturas contaminadas foram os fatores responsáveis pelo aumento da agregação dos filamentos de A. granulata nas culturas contaminadas