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Kirpenko, N. I. "Photosynthetic Activity of Algae in Their Mono- and Mixed Cultures." Hydrobiological Journal 45, no. 4 (2009): 61–73. http://dx.doi.org/10.1615/hydrobj.v45.i4.60.
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Battaglia, Manuela, Marco Andreani, Marisa Manna, Sonia Nesci, Paola Tonucci, Barbara Persini, Gioacchino Robustelli della Cuna, et al. "Coexistence of Two Functioning T-Cell Repertoires in Healthy Ex-Thalassemics Bearing a Persistent Mixed Chimerism Years After Bone Marrow Transplantation." Blood 94, no. 10 (November 15, 1999): 3432–38. http://dx.doi.org/10.1182/blood.v94.10.3432.422k17_3432_3438.
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Bone marrow transplantation (BMT) from an HLA-identical donor is an established therapy to cure homozygous β-thalassemia. Approximately 10% of thalassemic patients developed a persistent mixed chimerism (PMC) after BMT characterized by stable coexistence of host and donor cells in all hematopoietic compartments. Interestingly, in the erythrocytic lineage, close to normal levels of hemoglobin can be observed in the absence of complete donor engraftment. In the lymphocytic lineage, the striking feature is the coexistence of immune cells. This implies a state of tolerance or anergy, raising the issue of immunocompetence of the host. To understand the state of the T cells in PMC, repertoire analysis and functional studies were performed on cells from 3 ex-thalassemics. Repertoire analysis showed a profound skewing. This was due to an expansion of some T cells and not to a collapse of the repertoire, because phytohemagglutinin stimulation showed the presence of a complex repertoire. The immunocompetence of the chimeric immune systems was further established by showing responses to alloantigens and recall antigens in vitro. Both host and donor lymphocytes were observed in the cultures. These data suggest that the expanded T cells play a role in specific tolerance while allowing a normal immune status in these patients.
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Kaewsuk, Jutamas, Worachat Thorasampan, Monthon Thanuttamavong, and Gyu Tae Seo. "Kinetic development and evaluation of membrane sequencing batch reactor (MSBR) with mixed cultures photosynthetic bacteria for dairy wastewater treatment." Journal of Environmental Management 91, no. 5 (May 2010): 1161–68. http://dx.doi.org/10.1016/j.jenvman.2010.01.012.
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Bolinesi, Francesco, Maria Saggiomo, Serena Aceto, Angelina Cordone, Emanuela Serino, Maria Carmen Valoroso, and Olga Mangoni. "On the Relationship between a Novel Prorocentrum sp. and Colonial Phaeocystis antarctica under Iron and Vitamin B12 Limitation: Ecological Implications for Antarctic Waters." Applied Sciences 10, no. 19 (October 5, 2020): 6965. http://dx.doi.org/10.3390/app10196965.
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We collected live mixed natural samples from the northeastern Ross Sea during the austral summer of 2017 and isolated a novel Prorocentrum sp. (Dinophyceae) associated with mucilaginous Phaeocystis antarctica (Coccolithophyceae) colonies. The haptophyte P. antarctica is a key species of the phytoplankton community in the Ross Sea, where blooms are subjected to iron limitation and/or co-limitation with other micronutrients (e.g., vitamin B12) during the summer. We first performed preliminary genetic analyses to determine the specific identity of the novel Prorocentrum sp., which indicated that it represented a previously undescribed species. The formal description of this new species is in process. To further assess its relationship with P. antarctica, we obtained their monospecific and mixed cultures and evaluated their responses to different irradiance levels and iron and vitamin B12 limitation. Our results indicated differential susceptibility of the two species to iron limitation and differential photosynthetic plasticity under high irradiance. Iron limitation reduced colony formation in P. antarctica and decreased the chlorophyll-a content in Prorocentrum sp., whereas B12 limitation did not affect growth or photosynthetic efficiency in either species. In addition, P. antarctica could photosynthesize efficiently under different irradiance levels, due to its ability to modulate the light adsorption cross-section of PSII, whereas Prorocentrum sp. exhibited lower photosynthetic plasticity and an inability to modulate both the maximum photochemical efficiency and effective adsorption cross-section of PSII under high irradiance. The trophic interaction between Prorocentrum sp. and P. antarctica could present ecological implications for the food webs and biogeochemical cycles of the Antarctic ecosystem. Considering the predicted climate-driven shifts in global ocean surface light regimes and changes in iron or vitamin B12 transfer, which are most likely to impact changes in the phytoplankton community structure, our results present implications for carbon export to deeper waters, ecological functioning, and associated biogeochemical changes in the future.
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Hastuti, Sri, Tri Martini, Candra Purnawan, Abu Masykur, and Atmanto Heru Wibowo. "Pembuatan Kompos Sampah Dapur dan Taman dengan Bantuan Aktivator EM4." Proceeding of Chemistry Conferences 6 (September 15, 2021): 18. http://dx.doi.org/10.20961/pcc.6.0.55084.18-21.
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<p>Pembuatan kompos dari sampah dapur dan taman dengan bantuan <em>effective microorganism</em> (EM4) dan <em>microorganism local</em> (MOL) telah dilakukan. Tujuan dari kegiatan ini adalah memanfaatkan sampah yang ada di sekitar untuk dijadikan barang yang lebih berguna. EM4 merupakan kultur campuran dari mikroorganisme yang menguntungkan yang mengandung mikroorganisme fermentasi dan sintetik yang terdiri dari bakteri Asam Laktat (<em>Lactobacillus Sp</em>), bakteri Fotosentetik (<em>Rhodopseudomonas Sp</em>), <em>Actinomycetes Sp</em>, <em>Streptomyces Sp</em> dan Yeast (ragi) dan Jamur pengurai selulose. Bahan ini membantu fermentasi bahan organik tanah menjadi senyawa organik yang mudah diserap oleh akar tanaman. Proses pembuatan kompos dilakukan dengan mencampurkan sampah dapur dan taman dengan penambahan EM4. Proses fermentasi dilakukan variasi waktu 10, 14, 21, 26 dan 32 hari. Hasil pengamatan menunjukkan bahwa semakin lama fermentasi kompos yang dihasilkan semakin baik dimana daun telah hancur berubah bentuk seperti tanah.</p><p><strong><em>Kitchen and Garden Waste Composting using EM4 Activator. </em></strong><em>Composting of kitchen and garden waste with the help of effective microorganisms (EM4) and microorganism local (MOL) has been carried out. The purpose of this activity is to use the waste to become more useful items. EM4 is a mixed culture of beneficial microorganisms. This material contains microorganisms consisting of lactic acid bacteria (Lactobacillus Sp), photosynthetic bacteria (Rhodopseudomonas Sp), Actinomycetes Sp, Streptomyces Sp, and yeast, and cellulose-decomposing fungi. This activator helps break down soil organic matter into organic compounds that are easily absorbed by plant roots. The composting was done by mixing kitchen and garden waste with the addition of EM4 and MOL. The fermentation process was carried out in variations of 10, 14, 21, 26, and 32 days. The results showed that the longer the fermentation time the better the compost was produced indicating by the leaves had crumbled into shape like the soil.</em></p>
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Wong, SC, and CB Osmond. "Elevated Atmosphere Partial Pressure of CO2 and Plant Growth. III. Interactions Between Triticum aestivum (C3) and Echinochloa frumentacea (C4) During Growth in Mixed Culture Under Different CO2, N Nutrition and Irradiance Treatments, With Emphasis on Below-Ground Responses Estimated Using the δ13C Value of Root Biomass." Functional Plant Biology 18, no. 2 (1991): 137. http://dx.doi.org/10.1071/pp9910137.
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Wheat (Triticum aestivum L.), a C3 species, and Japanese millet (Echinochloa frumentacea Link), a C4 species, were grown in pots in monoculture and mixed culture (2 C3 : 1 C4 and 1 C3:2 C4) at two ambient partial pressures of CO2 (320 and 640 μbar), two photosynthetic photon flux densities (PPFDs) (daily maximum 2000 and 500 �mol m-2 s-1) and two levels of nitrogen nutrition (12 mM and 2 mM NO3-). Growth of shoots of both components in mixed culture was measured by physical separation, and the proportions of root biomass due to each component were calculated from δ13C value of total root biomass. In air (320 μbar CO2) at high PPFD and with high root zone-N, the shoot biomass of C3 and C4 components at the first harvest (28 days) was in proportion to the sowing ratio. However, by the second harvest (36 days) the C4 component predominated in both mixtures. Under the same conditions, but with low PPFD, C3 plants predominated at the first harvest but C4 plants had over- taken them by the time of the second harvest. Elevated atmospheric CO2 (640 μbar) stimulated shoot growth of Triticum in 15 of 16 treatment combinations and the stimulation was greatest in plants provided with low NO3-. Root growth of the C3 plants was generally stimulated by elevated CO2, but was only occasionally sensitive to the presence of C4 plants in mixed culture. However, growth of the C4 plants was often sensitive to the presence of C3 plants in mixed culture. In mixed cultures, elevated CO2 plants stimulated growth of C4 plants at high PPFD, high-N and in all low-N treatments but this was insufficient to offset a marked decline in shoot growth with increasing proportion of C3 plants in mixed cultures. The unexpected stimulation of growth of C4 plants by elevated CO2 was correlated with more negative δ13C values of C4 root biomass, suggesting a partial failure of the CO2 concentrating mechanism of C4 photosynthesis in Echinochloa under low-N. These experiments show that for these species nitrogen was more important than light or elevated pCO2 in determining the extent of competitive interactions in mixed culture.
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Mašková, Petra, Barbora Radochová, Zuzana Lhotáková, Jan Michálek, and Helena Lipavská. "Nonstructural carbohydrate-balance response to long-term elevated CO2 exposure in European beech and Norway spruce mixed cultures: biochemical and ultrastructural responses." Canadian Journal of Forest Research 47, no. 11 (November 2017): 1488–94. http://dx.doi.org/10.1139/cjfr-2017-0083.
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Two dominant central European tree species (Fagus sylvatica L. and Picea abies (L.) Karst.), in a mixed culture in semi-open glass domes, were used to simulate the reaction of forests to long-term elevated CO2 (EC) in a mountainous area (Beskydy Mountains, the Czech Republic). We investigated the effects of EC on soluble carbohydrate levels and composition. Starch content was evaluated using two methods: biochemical (glucose content after enzymatic hydrolysis) and stereological (starch grain proportion, size, and number in chloroplasts). In beech and spruce foliage, no significant changes in total soluble carbohydrate levels were observed. In spruce, starch content determined biochemically increased under EC, whereas no changes were detected in beech. The starch content determined stereologically increased only in beech. In spruce, EC exposure caused comparable starch increases in current-year and previous-year needles, although the former had a higher starch content and numerous larger starch grains regardless of CO2 concentration. In both species, the biochemical determination of carbohydrates exhibited greater individual tree uniformity, in contrast to large intraspecies variability. No changes in leaf soluble carbohydrates under long-term elevated CO2 demonstrate the ability of the studied tree species to efficiently allocate the photosynthates among the sinks. Thus, no photosynthetic downregulation via carbohydrate-level signalling can be expected.
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Rajaii, Mahdieh, and Mehdi DahMardeh. "The Evaluation of Corn and Peanut Intercropping on Efficiency of Use the Environmental Resource and Soil Fertility." Journal of Agricultural Science 6, no. 4 (March 15, 2014): 99. http://dx.doi.org/10.5539/jas.v6n4p99.
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Order to study the effect of density, the control weed and various proportion corn (704 Variety) and peanut (Goli Variety) intercropping an experiment was conducted in 2012 in Research station of agriculture, University of Zabol. The experiment design was factorial in randomized complete block design with three replications. Experiment factors consisted of planting proportions in 4 levels (sole crop of corn, 50% corn + 50% peanut, 100% corn + 100% peanut and sole crop of peanut), control weed in 3 levels (non-weeding, once-weeding and twice-weeding) and the space between rows in 2 level (40 and 50 cm) has been considered. The evaluated Characteristics in environmental sources are (Photosynthetic Active Radiation, Temperature and soil Moisture), the nutrients of soil include (N, K, Na, Mg, Ca, and C) and to evaluate intercropping of pure was used land equivalent ratio and economical yield. All Characteristics of study were affected by planting system.There was significant interaction between planting system, weeding and density in the absorption of light, temperature and moisture of soil. The results showed that photosynthesis active radiation absorbed by the intercropping was higher than sole crop in both plants. The results showed that changes in soil nutrient capacity of single elements (Na and K) in the treatment of mixed and monoculture peanut was more than monoculture corn and divalent elements (Ca and Mg) in mixed and monoculture corn more than mixed replacement and peanut monoculture. The highest land equivalent ratio (1.048) was accounted additive intercropping. Generally the mixed cultures with increasing density and control weed caused increase soil fertility and amount of soil nutrients after harvest. Treatment 100% Corn +100% peanut was the best treatment because using sources and increasing soil fertility and crop yield in comparison to sole crop.
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Zagrodnik, Roman. "Optimization of Hydrogen Production by Co-Culture of Clostridium beijerinckii and Rhodobacter sphaeroides Bacteria." Advances in Science and Technology 93 (October 2014): 90–95. http://dx.doi.org/10.4028/www.scientific.net/ast.93.90.
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The biological methods of hydrogen generation have attracted a significant interest recently. In this work the hybrid system applying both dark fermentation bacteria in co-culture was tested. Objective of this work was to investigate the optimization of different parameters on co-culture of Clostridium beijerinckii DSM-791 and Rhodobacter sphaeroides O.U.001. The effect of glucose concentration (1–5 g/L), temperature and initial pH (6,5–7,5) was analyzed. Moreover the influence of organic nitrogen sources were tested for their capacity to support hydrogen production (yeast extract, peptone, glutamic acid). Fermentations were conducted in batch tests with glucose as sole substrate. Hydrogen production in mixed culture was compared with pure cultures. The process was greatly affected by pH and light/dark bacteria ratio. Liquid metabolites, namely acetic and butyric acids, from the dark fermentation step were the source of organic carbon for photosynthetic bacteria. This increased the hydrogen yield in comparison to single-step dark fermentation to over 4 mol H2/mol glucose. Obtained results showed that combination of photo and dark fermentation may increase hydrogen production and conversion efficiency of complex substrates or wastewaters.
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Sundstrom, Eric R., and Craig S. Criddle. "Optimization of Methanotrophic Growth and Production of Poly(3-Hydroxybutyrate) in a High-Throughput Microbioreactor System." Applied and Environmental Microbiology 81, no. 14 (May 8, 2015): 4767–73. http://dx.doi.org/10.1128/aem.00025-15.
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ABSTRACTProduction of poly(3-hydroxybutyrate) (P3HB) from methane has economic and environmental advantages over production by agricultural feedstock. Identification of high-productivity strains and optimal growth conditions is critical to efficient conversion of methane to polymer. Current culture conditions, including serum bottles, shake flasks, and agar plates, are labor-intensive and therefore insufficient for systematic screening and isolation. Gas chromatography, the standard method for analysis of P3HB content in bacterial biomass, is also incompatible with high-throughput screening. Growth in aerated microtiter plates coupled with a 96-well Nile red flow-cytometric assay creates an integrated microbioreactor system for high-throughput growth and analysis of P3HB-producing methanotrophic cultures, eliminating the need for individual manipulation of experimental replicates. This system was tested in practice to conduct medium optimization for P3HB production in pure cultures ofMethylocystis parvusOBBP. Optimization gave insight into unexpected interactions: for example, low calcium concentrations significantly enhanced P3HB production under nitrogen-limited conditions. Optimization of calcium and copper concentrations in the growth medium increased final P3HB content from 18.1% to 49.4% and P3HB concentration from 0.69 g/liter to 3.43 g/liter while reducing doubling time from 10.6 h to 8.6 h. The ability to culture and analyze thousands of replicates with high mass transfer in completely mixed culture promises to streamline medium optimization and allow the detection and isolation of highly productive strains. Applications for this system are numerous, encompassing analysis of biofuels and other lipid inclusions, as well as analysis of heterotrophic and photosynthetic systems.
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Pereira, Marcos Gervasio, Arcangelo Loss, Roni Fernandes Guareschi, Fabiana Da Costa Barros, Marisa De Cássia Piccolo, Adriano Perin, Francirose Shigaki, and Otavio Augusto Queiroz Dos Santos. "PHYSICAL ATTRIBUTES, TOTAL CARBON AND 13C NATURAL ABUNDANCE IN FERRALSOL UNDER DIFFERENT AGRICULTURAL SYSTEMS." International Journal of Research -GRANTHAALAYAH 8, no. 5 (June 10, 2020): 266–76. http://dx.doi.org/10.29121/granthaalayah.v8.i5.2020.205.
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The objective of this study was to evaluate the bulk density, total pore volume, carbon stock and natural abundance of 13C in Rhodic Ferralsol in no-tillage system (NTS) areas under different succession and rotation of cultures in the Cerrado of Goiás State, Brazil. In order to do so, NTS areas were selected in Montividiu, Goiás, under the same soil and climatic conditions as the following rotations: soybean-corn succession, soybean-millet succession, soybean-corn-millet-beans-cotton rotation, soybean-corn-brachiaria succession and a pasture area (PA), used as a control. In each area, samples were collected at depths of 0.0–0.05, 0.05–0.10, 0.10–0.20, and 0.20–0.40 m. The lowest levels of carbon content and stocks were verified in PA in comparison to the other areas evaluated. The NTS with soybean-corn-millet-beans-cotton crop rotation followed by NTS with soybean-corn-brachiaria succession were those that presented greater potential for carbon stock increase and total soil pore volume, as well as bulk density reduction. The origin of the soil organic matter in the NTS areas is related to plants employing the C4 photosynthetic cycle; however, for mixed C3 and C4 plant systems, the isotopic signature of 13C is reduced, mainly in areas with crop rotation.
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Kirkwood, A. E., C. Nalewajko, and R. R. Fulthorpe. "The impacts of cyanobacteria on pulp-and-paper wastewater toxicity and biodegradation of wastewater contaminants." Canadian Journal of Microbiology 51, no. 7 (July 1, 2005): 531–40. http://dx.doi.org/10.1139/w05-030.
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This study investigated the effects of cyanobacteria from pulp-and-paper waste-treatment systems on biological toxicity removal and biodegradation of certain wastewater contaminants. In field and batch studies, using the Microtox®assay, cyanobacterial biomass and final wastewater toxicity were significantly correlated. In softwood-based wastewater, a decrease in toxicity was negatively correlated with cyanobacterial biomass, but the correlation was positive in hardwood-based wastewater. In the softwood-based wastewater, toxicity remained higher in the light than it was in the dark, whereas in hardwood-based wastewater, toxicity was lower in the light than it was in the dark. All of these results were light-dependent, suggesting that the photosynthetic growth of cyanobacteria is required to induce significant effects. When grown in mixed cultures with bacterial degraders, cyanobacteria from pulp-and-paper waste-treatment systems generally impeded the biodegradation of the wastewater contaminants phenol and dichloroacetate (DCA). However, there was one case where the cyanobacterium Phormidium insigne improved the bacterial degradation of DCA. Doubling inorganic nutrient concentrations did not improve phenol or DCA biodegradation in the majority of cases, indicating that nutrient competition is not a major factor. These data suggest that cyanobacteria play an important role during the biological treatment of contaminants, and, hence, toxicity removal in pulp-and-paper waste-treatment systems.Key words: cyanobacteria, heterotrophic bacteria, biodegradation, pulp and paper waste-treatment, wastewater toxicity.
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Elfiza, Wahida Nia, Abdi Dharma, and Nasril Nasir. "Penapisan Mikroalga Penghasil Karotenoid serta Studi Pengaruh Stres Nitrogen dan Fosfor terhadap Produksi B-Karoten pada Mikroalga Oocystis sp." Jurnal Pascapanen dan Bioteknologi Kelautan dan Perikanan 14, no. 1 (June 28, 2019): 9. http://dx.doi.org/10.15578/jpbkp.v14i1.598.
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Abstrakb-karoten merupakan karotenoid yang bermanfaat sebagai antioksidan. Penelitian ini bertujuan menapis mikroalga yang berpotensi mengandung karotenoid tinggi dan mempelajari pengaruh nitrogen dan fosfor terhadap produktivitas biomassa, kandungan pigmen fotosintesis dan b-karoten, pada mikroalga yang diisolasi dari perairan Danau Atas, Sumatra Barat. Penapisan mikroalga penghasil karotenoid dilakukan dengan memberikan paparan UV-A 326 nm terhadap kultur campuran mikroalga. Hasil penelitian menunjukkan bahwa 5 dari 18 spesies mampu bertahan pada proses penapisan. Pengaruh 9 jenis medium pertumbuhan dengan kriteria: tanpa NaNO3, 3x NaNO3, 5x NaNO3, 10x NaNO3, Bold Basalt Medium (BBM) normal (kontrol), tanpa KH2PO4, 3x KH2PO4, 5x KH2PO4,dan10x KH2PO4 terhadap mikroalga terpilih (Oocystis sp.) diamati. Hasil menunjukkan kandungan b-karoten tertinggi ditemukan pada perlakuan 5x KH2PO4 yaitu sebesar 0,22 % dari berat kering mikroalga, dengan produktivitas biomassa 0,0015 g/mL/hari, serta kandungan klorofil a, klorofil b dan karotenoid total yaitu 7,15 µg/mL, 0,81 µg/mL dan 6,67 µg/mL. Berdasarkan penelitian ini dapat disimpulkan medium pertumbuhan dengan kandungan 5x KH2PO4 merupakan medium yang cocok bagi pertumbuhan Oocystis sp. untuk mendapatkan biomassa dengan kandungan b-karoten dan karotenoid tinggi tanpa harus menurunkan produktivitas biomassanya. Screening of Carotenoid Producing Microalgae and Study of the Effect of Nitrogen and Phosphorus Stress on the Production of b-Carotene in Microalgae Oocystis sp.Abstractb-carotene is a carotenoid that is useful as an antioxidant. Present study aims to screening high microalgae which contain carotenoids from water of Danau Atas lake (West Sumatra Province), and study the effect of nitrogen and phosphorus on biomass productivity, photosynthetic and b-carotene pigment content. Screening of carotenoid-producing microalgae was carried out by exposing UV-A 326 nm to mixed microalgae cultures. The results showed that 5 of the 18 species were able to survive in the screening process. The effect of growth medium, i.e. without NaNO3, 3x NaNO3, 5x NaNO3, 10x NaNO3, normal Bold Basalt Medium (BBM) (control), without KH2PO4, 3x KH2PO4, 5x KH2PO4, and 10x KH2PO4 on of selected microalgae (Oocystis sp.) was carried out. The result showed that the highest content of b-carotene of Oocystis sp. was obtained with 5x KH2PO4 which was 0.22% of the dry weight of biomass. Biomass productivity was 0.0015 g/mL/day and the chlorophyll a, chlorophyll b and total carotenoids contents were 7.15 µg/mL, 0.81 µg/mL and 6.67 µg/mL, respectively. Based on this research, 5x KH2PO4 can be concluded as a suitable medium for Oocystis sp. to obtained high b -carotene and carotenoid of Oocystis sp. without reducing biomass productivity.
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Fiori, Emanuela, Nayani K. Vidyarathna, Johannes A. Hagström, Rossella Pistocchi, and Edna Granéli. "Influence of Light on Prymnesium Parvum Growth, Toxicity and Mixotrophy." Linnaeus Eco-Tech, February 1, 2017. http://dx.doi.org/10.15626/eco-tech.2012.025.
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The haptophyte Prymnesium parvum has a worldwide distribution, with dramatic increase in blooms in the last years. P. parvum blooms are often associated with massive fish kills and great ecological impacts and economic losses as a consequence. P. parvum is a mixotrophic organism, utilizing organic dissolved substances and particles to support its photosynthetic growth. The ability of P. parvum to produce toxic compounds, and being a mixotroph, makes it capable to outcompete other algal species for essential substances. These mechanisms are mostly enhanced when environmental conditions are not optimal for P. parvum growth. Here we report results on the growth, toxicity and mixotrophy, from experiments where P. parvum cells were grown as monocultures or together with Rhodomonas salina and exposed to different light conditions (dark, 100, 700, 2000 μmol photons m-2 s-1). The results showed that P. parvum growth is affected at light intensity of 700 μmol photons m-2 s-1 and the cells were photo-lysed when exposed to irradiances above this value. An inverse relationship between cellular toxicity and light intensity was observed, i.e. lower light irradiation induced higher cell toxicity. Phagotrophy was observed in all the conditions. P. parvum reached significantly higher cell densities when growing together with R. salina than in monocultures, while cellular toxicity was significantly reduced in the mixed cultures. Furthermore the presence of prey attenuated the negative effect of the higher irradiations on P. parvum growth.
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Ma, Zengling, Hengguo Yu, Ronald Thring, Chuanjun Dai, Anglv Shen, and Min Zhao. "Interaction between simulated dense Scenedesmus dimorphus (Chlorophyta) bloom and freshwater meta-zooplankton community." Journal of Limnology 77, no. 2 (March 8, 2018). http://dx.doi.org/10.4081/jlimnol.2018.1742.
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Algal bloom has been a subject of much research, especially the occurrence of blue-green algae (cyanobacteria) blooms and their effects on aquatic ecosystems. However, the interaction between green algae blooms and zooplankton community was rarely investigated. In the present study, the effects exerted by Scenedesmus dimorphus (green alga) bloom on the community structure of zooplankton and the top-down control of the bloom process mediated by the zooplankton were evaluated using a series of laboratory cultures. The results showed that a dense S. dimorphus bloom could change the zooplankton community structure by decreasing its diversity indices, leading to the enrichment of a particular zooplankton species, Brachionus calyciflorus. In the presence of mixed species of zooplankton, the density of S. dimorphus in the culture was decreased as determined by a change in total chlorophyll a (Chl a) concentration, which was about 200 μg L-1 lower than that of the zooplankton-free culture. Furthermore, the number of species belonging to Cladocera, Copepoda and Rotifera all decreased, with all the cladocerans disappeared in the co-culture within 2 weeks of culturing, while the density of rotifers increased from 818 (±243) ind L-1 at the time of inoculation to 40733 (±2173) ind L-1 on the 14th day post-inoculation. Grazing of S. dimorphus by the rotifer B. calyciflorus neutralized its growth, and the gradual increase in B. calyciflorus density eventually led to the collapse of the bloom. Furthermore, grazing by B. calyciflorus also led to a decrease in the maximal photochemical efficiency (Fv/Fm) of photosystem II (PSII). The combined changes occurring in the zooplankton community structure during the process of S. dimorphus bloom and the negative effects of grazing on algal growth, morphology and photosynthetic activities confirmed the key role of zooplankton in the control of algal bloom. The results of the study therefore indicated that dense algal blooms caused by non-toxic algae could still remain a threat to aquatic ecosystems.
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Biller, Steven J., Allison Coe, Sara E. Roggensack, and Sallie W. Chisholm. "Heterotroph Interactions AlterProchlorococcusTranscriptome Dynamics during Extended Periods of Darkness." mSystems 3, no. 3 (May 29, 2018). http://dx.doi.org/10.1128/msystems.00040-18.
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ABSTRACTMicrobes evolve within complex ecological communities where biotic interactions impact both individual cells and the environment as a whole. Here we examine how cellular regulation in the marine cyanobacteriumProchlorococcusis influenced by a heterotrophic bacterium,Alteromonas macleodii, under different light conditions. We monitored the transcriptome ofProchlorococcus, grown either alone or in coculture, across a diel light:dark cycle and under the stress of extended darkness—a condition that cells would experience when mixed below the ocean’s euphotic zone. MoreProchlorococcustranscripts exhibited 24-h periodic oscillations in coculture than in pure culture, both over the normal diel cycle and after the shift to extended darkness. This demonstrates that biotic interactions, and not just light, can affect timing mechanisms inProchlorococcus, which lacks a self-sustaining circadian oscillator. The transcriptomes of replicate pure cultures ofProchlorococcuslost their synchrony within 5 h of extended darkness and reflected changes in stress responses and metabolic functions consistent with growth cessation. In contrast, when grown withAlteromonas, replicateProchlorococcustranscriptomes tracked each other for at least 13 h in the dark and showed signs of continued biosynthetic and metabolic activity. The transcriptome patterns suggest that the heterotroph may be providing energy or essential biosynthetic substrates toProchlorococcusin the form of organic compounds, sustaining this autotroph when it is deprived of solar energy. Our findings reveal conditions where mixotrophic metabolism may benefit marine cyanobacteria and highlight new impacts of community interactions on basicProchlorococcuscellular processes.IMPORTANCEProchlorococcusis the most abundant photosynthetic organism on the planet. These cells play a central role in the physiology of surrounding heterotrophs by supplying them with fixed organic carbon. It is becoming increasingly clear, however, that interactions with heterotrophs can affect autotrophs as well. Here we show that such interactions have a marked impact on the response ofProchlorococcusto the stress of extended periods of darkness, as reflected in transcriptional dynamics. These data suggest that diel transcriptional rhythms withinProchlorococcus, which are generally considered to be strictly under the control of light quantity, quality, and timing, can also be influenced by biotic interactions. Together, these findings provide new insights into the importance of microbial interactions onProchlorococcusphysiology and reveal conditions where heterotroph-derived compounds may support autotrophs—contrary to the canonical autotroph-to-heterotroph trophic paradigm.