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Stefanie F Kuhn - One of the best experts on this subject based on the ideXlab platform.
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pH effect on the susceptibility to parasitoid infection in the marine diatom Coscinodiscus spp. (Bacillariophyceae)
Marine Biology, 2008Co-Authors: Stefanie F Kuhn, Stephanie Köhler-rinkAbstract:The pH on the frustule of individual cells of the marine centric diatoms Coscinodiscus granii and Coscinodiscus wailesii (Bacillariophyceae) was measured with pH microsensors in culture media with increasing pH values of 8.04, 8.14, and 8.22, respectively. In 85–96% of the C. granii cells the pH on the frustule was up to 0.4 units higher than that of the medium, reaching a maximum pH 8.95. Only in 2–3% the surface pH exceeded that of the medium by up to 0.7 pH units. These results strongly suggest that diatoms in batch cultures differ, at least temporarily, in their individual photosynthetic activities. Infection experiments with the parasitoid nanoflagellate Pirsonia diadema (Stramenopile) showed that flagellates failed to infect when the culture pH was 8.8 and above. pH measurements on freshly infected C. granii showed that the prevalence of infection was higher in tendency on diatoms with low surface pH. Application of these results to parasitoid-diatom interactions in natural waters suggests that within phytoplankton populations a strong photosynthetic activity might prevent diatom cells temporarily from infection by pH-sensitive parasitoids.
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membrane organisation and dynamics in the marine diatom Coscinodiscus wailesii bacillariophyceae
Botanica Marina, 2005Co-Authors: Stefanie F Kuhn, Colin BrownleeAbstract:The membrane dye FM1-43 was used to visualise membrane internalisation in living cells of the marine centric diatoms Coscinodiscus wailesii and Thalassiosira punctigera. The results revealed dynamic and selective membrane trafficking and several cellular structures which have not been described in light microscopical studies. Intimate and regular contacts were found between the plasma membrane and the labiate processes and the inner face of the frustule in C. wailesii. The central cytoplasmic region close to the tonoplast and growing parts of the silica deposition vesicles became labelled, indicating that they were involved in membrane recycling. We never observed labelling of chloroplasts, nucleus or the vacuolar contents. These studies also revealed a novel perinuclear region that appeared not to show significant membrane turnover. When the cytoplasm was impaled with a micropipette, membranous material rapidly accumulated at the tip of the micropipette, presumably expelling it from the protoplast. This could be an effective defence mechanism against certain invasive pathogens, and further illustrates the highly dynamic nature of the endomembrane system.
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infection of Coscinodiscus spp by the parasitoid nanoflagellate pirsonia diadema ii selective infection behaviour for host species and individual host cells
Journal of Plankton Research, 1998Co-Authors: Stefanie F KuhnAbstract:The parasitoid nanoflagellate (PNF) Pirsonia diadema is host specific for the marine centric diatom Coscinodiscus spp. Experiments showed that flagellates significantly prefer C.wailesii over Cgranii as host species (interspecific selectivity). This preference was independent of light conditions (dark, irradiance of 10 and 70 umol m~2 s~') and temperature (10 and 15°C). Among unicellular host diatoms, the infection behaviour was selective for individual cells: already infected Cgranii cells were more attractive for further flagellate attachment than non-infected cells (intraspecific selectivity). Individual cells (-1%) remained uninfected for some time. Coscinodiscus granii cultures kept in darkness were more rapidly infected than those kept in the light. It is suggested that photosynthesis enhances the formation of individual physiological properties of diatoms leading to intraspecific vari- ability of susceptibility.
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infection of Coscinodiscus spp by the parasitoid nanoflagellate pirsonla diadema i behavioural studies on the infection process
Journal of Plankton Research, 1997Co-Authors: Stefanie F KuhnAbstract:The investigation of successive steps involved in the infection process of the marine diatoms Coscinodiscus granii and Coscinodiscus waUesii by the host-specific parasitoid nanoflagellate (PNF) Pirsonia diadema showed that flagellates reacted chemoklinokinetically with changes of swimming pattern to the presence of a host diatom. Chemosensory stimulation appeared to induce readiness for infection, whereas attachment and penetration of the diatom cell wall was induced by a mechanosen- sory response to morphological features on the diatom frustules. The mean swimming speed of P.diadema flagellates decreased during their infective lifetime of 3 days from an average of 78 urn s"1 to 51 um s" 1, while the frequency of small loops in the swimming pattern increased from 0.8 to 6.3 loops min~'. At high Cgranii densities, an epidemic was delayed. It is suggested that this could be caused by overlapping gradients of extracellular material released by the diatoms which impaired the sensing of spatial gradients by PNF and, therefore, the location of hosts.
Anna-maria M. Schmid - One of the best experts on this subject based on the ideXlab platform.
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ultrastructure of the male gametes from two centric diatoms chaetoceros laciniosus and Coscinodiscus wailesii bacillariophyceae
Phycologia, 2003Co-Authors: Karin G Jensen, Ojvind Moestrup, Anna-maria M. SchmidAbstract:Abstract The ultrastructure of the male gametes of two centric diatom species, Coscinodiscus wailesii and Chaetoceros laciniosus, is described. The species differ in the presence and configuration of certain organelles and structures, e.g. chloroplasts, Golgi bodies and microtubules (MTs), but both display a deviant configuration of the flagellar apparatus, as in other diatoms that have been examined, viz. a 9 + 0 microtubular configuration in the flagellar axoneme and a ring of nine doublets of MTs in the basal body. MTs were seen to arise from the basal body; in Coscinodiscus wailesii, the MTs formed several small bundles, which radiated in all directions from the basal body and extended down into the cell, whereas in Chaetoceros laciniosus only one bundle of MTs was observed, which was associated with the nucleus. Both species possessed two transitional plates in the flagellar transition region, one at the level of the plasmalemma, the other – less distinct – further into the basal body.
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slit scales in the auxospore scale case of Coscinodiscus granii the rudiments of rimoportulae
Diatom Research, 1994Co-Authors: Anna-maria M. SchmidAbstract:The scale case of the auxospores of Coscinodiscus granii is composed of two types of scales: the typical scale type, found commonly in auxospores, and constituting the majority of the cell's investment, and intermingled, a limited number of scales possessing a clear slit in the central area circumscribed by the annulus. Their sum approximates the sum of the rimoportulae in a valve (63–65) of this species. It is suggested that they may be the pre-stages of the rimoportulae in Coscinodiscus.
M De Stefano - One of the best experts on this subject based on the ideXlab platform.
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interfacing the nanostructured biosilica microshells of the marine diatom Coscinodiscus wailesii with biological matter
Acta Biomaterialia, 2008Co-Authors: L De Stefano, Annalisa Lamberti, Lucia Rotiroti, M De StefanoAbstract:Biosilicified nanostructured microshells from the marine diatom Coscinodiscus wailesii have been properly functionalised to bind a molecular probe which specifically recognises a target analyte. The chemical modification process has been characterised by Fourier transformed infrared spectroscopy. Fluorescence measurements demonstrate that the antibodies we used, even if linked to the amorphous silica surface of C. wailesii microshells, still efficiently recognise their antigens. These low cost and largely available natural materials can be thus used as transducers elements for optical biosensors or as targeting microcapsules for drug delivery.
Carl M Boyd - One of the best experts on this subject based on the ideXlab platform.
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electrophysiology of the marine diatom Coscinodiscus wailesii ii potassium currents
Journal of Experimental Botany, 1999Co-Authors: Dietrich Gradmann, Carl M BoydAbstract:upon changes in [K+] o , are well described by a threestate reaction cycle for catalysis of K+ translocation The dominating mechanism of K+ uniport through the with a steady activity. plasmalemma of Coscinodiscus wailesii has been studied in some detail as part of a general study of Key words: Coscinodiscus, current‐voltage relationships, ionic relations in marine diatoms. Electrical measure- diatoms, inward rectification, phytoplankton, potassium ments with double-barrelled glass-microelectrodes selectivity. have been made in intact cells (diameter #250 mm, height #100 mm) bathed in artificial sea-water in Introduction which [K+] has been changed from 3 mM to 100 mM. Using a modified Goldman equation, these results Marine diatoms are of global importance as they accomprovide an estimate of [K+] i of about 400 mM and a plish about 20‐25% of the earth’s assimilation ( Werner, selectivity for K+ over Na+ and Cl’, which could spon- 1977). However, very little is known about their physitaneously vary by orders of magnitude and reach ology and especially their membranes. Gradmann and values of about 1000. Voltage-clamp experiments have Boyd (1995) have reported the first measurements of the been carried out in these states of high K+ selectivity membrane voltage of the marine diatom Coscinodiscus using bipolar staircase command voltages over a range radiatus. Methodological improvements of the medium from ’180 to +60 mV. The resulting steady-state cur- exchange and voltage-clamp system (Boyd and rent‐voltage relationships have inward rectifying sig- Gradmann, 1999a) and using a the larger species moid characteristics with a negative saturation current Coscinodiscus wailesii enabled a more detailed electroaround ’300 nA, a positive saturation current of about physiological characterization of the plasmalemma of 30 nA, and a slope conductance of the order of 1 mS these diatoms. Currently, this characterization consists of at free running voltages <’60 mV. Temporal a unique collection of new phenomena (Boyd and responses of the clamp currents upon rectangular volt- Gradmann, 1999a), of an electrophysiological investiage steps were basically rectangular, i.e. they did not gation of N-nutrition (Boyd and Gradmann, 1999b) and show the familiar relaxation kinetics of voltage- of this study which focuses on K+ relations. Since K+ induced activation/inactivation. The sigmoid steady- currents frequently dominate the electrophysiological state current‐voltage relationships could not be behaviour of biological membranes, the results of this described by a usual model of constant-field currents study are expected (a) to allow a comparison with known through a voltage-gated pore, where the positive cur- membranes, and (b) to provide reliable background rent of an inward rectifier would not saturate but knowledge for the interpretation of the electrophysiolovanish. Alternatively, the observed steady-state inward gical phenomena which comprise movement of ions other than K+.
Pablo Muniz - One of the best experts on this subject based on the ideXlab platform.
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Diatoms, protein and carbohydrate sediment content as proxies for coastal eutrophication in Montevideo, Rio de la Plata Estuary, Uruguay
Brazilian Journal of Oceanography, 2011Co-Authors: Felipe García-rodríguez, Laura Del Puerto, Natalia Venturini, Ana Laura Pita, Ernesto Brugnoli, Leticia Burone, Pablo MunizAbstract:A study on sediment surface diatom composition in relation to both protein/carbohydrate content and salinity was carried out in Montevideo Bay and the adjacent coastal zone. Samples were seasonally taken during one year along a human impact gradient, and the trophic conditions were assessed from the biochemical composition of the surface sediment organic matter. The co-occurrence of the marine-brackish (Actinocyclus curvatulus, Actinocyclus gallicus, Coscinodiscus excentricus, Coscinodiscus radiatus, Hyalodiscus subtilis, Paralia sulcata) and freshwater diatom flora (Aulacoseira granulata, Aulacoseira italica, Aulacoseira muzzanensis, Actinocyclus normanii, Amphora copulata, Cyclotella meneghiniana, Nitzschia linearis), suggests myxohaline estuarine conditions in the study area. The sampling stations located within the bay, close to several contamination sources, exhibited hypertrophic conditions as indicated by the highest levels of protein content, but also by the high relative abundances of Actinocyclus normanii and Cyclotella meneghiniana, as both diatom species are very well established cosmopolitan proxies of aquatic degradation. The levels of both protein and carbohydrate content, but also photosynthetic pigments, recorded in the adjacent coastal zone suggest meso-eutrophic conditions as contamination levels from the inner bay might become diluted off shore. Multivariate diatom species-environmental data relationships, indicate that the trophic gradient is hierarchically more important than salinity in explaining the diatom distribution. The present data imply an improvement in our ability of assessing organic contamination in the study area, since both biological and biopolymer variables were introduced for the first time as a tool for assessing the benthic health/degradation in one of the most populated regions of the Rio de la Plata.
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Diatoms, protein and carbohydrate sediment content as proxies for coastal eutrophication in Montevideo, Rio de la Plata Estuary, Uruguay
Universidade de São Paulo, 2011Co-Authors: Felipe García-rodríguez, Laura Del Puerto, Natalia Venturini, Ana Laura Pita, Ernesto Brugnoli, Leticia Burone, Pablo MunizAbstract:A study on sediment surface diatom composition in relation to both protein/carbohydrate content and salinity was carried out in Montevideo Bay and the adjacent coastal zone. Samples were seasonally taken during one year along a human impact gradient, and the trophic conditions were assessed from the biochemical composition of the surface sediment organic matter. The co-occurrence of the marine-brackish (Actinocyclus curvatulus, Actinocyclus gallicus, Coscinodiscus excentricus, Coscinodiscus radiatus, Hyalodiscus subtilis, Paralia sulcata) and freshwater diatom flora (Aulacoseira granulata, Aulacoseira italica, Aulacoseira muzzanensis, Actinocyclus normanii, Amphora copulata, Cyclotella meneghiniana, Nitzschia linearis), suggests myxohaline estuarine conditions in the study area. The sampling stations located within the bay, close to several contamination sources, exhibited hypertrophic conditions as indicated by the highest levels of protein content, but also by the high relative abundances of Actinocyclus normanii and Cyclotella meneghiniana, as both diatom species are very well established cosmopolitan proxies of aquatic degradation. The levels of both protein and carbohydrate content, but also photosynthetic pigments, recorded in the adjacent coastal zone suggest meso-eutrophic conditions as contamination levels from the inner bay might become diluted off shore. Multivariate diatom species-environmental data relationships, indicate that the trophic gradient is hierarchically more important than salinity in explaining the diatom distribution. The present data imply an improvement in our ability of assessing organic contamination in the study area, since both biological and biopolymer variables were introduced for the first time as a tool for assessing the benthic health/degradation in one of the most populated regions of the Río de la Plata.Foi realizado um estudo da salinidade e da composição das diatomáceas presentes no sedimento superficial em relação ao conteúdo de proteínas/carboidratos na Baía de Montevidéu e região costeira adjacente. Foram obtidas amostras sazonalmente durante um ano ao longo de um gradiente de impacto ambiental humano, e as condições tróficas foram determinadas através da análise da composição bioquímica da matéria orgânica do sedimento superficial. A coocorrência de espécies de diatomáceas marinhas-salobras, (Actinocyclus curvatulus, Actinocyclus gallicus, Coscinodiscus excentricus, Coscinodiscus radiatus, Hyalodiscus subtilis, Paralia sulcata) e diatomáceas indicadoras de águas doces (Aulacoseira granulata, Aulacoseira italica, Aulacoseira muzzanensis, Actinocyclus normanii, Amphora copulata, Cyclotella meneghiniana, Nitzschia linearis) sugerem condições mixohalinas estuarinas na área de estudo. As estações amostradas dentro da baía, próximas às fontes contaminadoras, apresentam condições hipertróficas apontadas pelos maiores valores de proteínas e pela alta abundância relativa de Actinocyclus normanii e Cyclotella meneghiniana, sendo que ambas espécies são consideradas cosmopolitas e indicadoras de degradação aquática. As concentrações de proteínas e carboidratos, bem como os pigmentos fotossintéticos registrados na região costeira adjacente sugerem condições meso-eutróficas e uma diluição dos níveis de contaminação do interior da baía rumo à região externa. A análise multivariada entre espécies de diatomáceas e parâmetros ambientais indica que o gradiente trófico possui hierarquicamente maior peso que a salinidade na explicação da distribuição das diatomáceas. Os resultados obtidos demonstram um aperfeiçoamento na habilidade de determinar a contaminação orgânica dentro da área de estudo, já que pela primeira vez tanto as variáveis orgânicas quanto os biopolímeros foram introduzidos como ferramenta para a determinação da relação degradação/saúde de uma das mais populosas regiões do Río de la Plata
