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Phaeocystis - a key organism in dimethylsulfoniopropionate production; ecological and physiological functions of DMSP
Füllsacková, Alena ; Němcová, Yvonne (advisor) ; Pusztai, Martin (referee)
Dimethylsulfoniopropionate (DMSP) is an organic sulfur compound with an important ecological and physiological functions. DMSP is a major precursor for dimethylsulfid (DMS). DMSP is produced by variety of halophytic plants and phytoplankton for the purposes of osmotic regulation, antioxidation and protection from predators. It is especially widespread among the marine phytoplankton and it is ubiquitous in the euphotic zone. DMS and DMSP are also involved in flux of carbon and sulfur. Marine emissions of DMS have a particularly important role as precursors of atmospheric sulfur-containing aerosols that influence the Earth's climate system through direct backscatter of solar radiation and through cloud formation. DMSP is produced mainly by phytoplankton, because this group of organism is very large, I'll focus on Phaeocystis. Phaeocystis is a genus of marine phytoplankton with a worldwide distribution. It has a polymorphic life cycle alternating free-living cells and colonies but develops massive blooms under the colony form. Among the 10 species, only 3 (P. pouchetii, P. antarctica, P. globosa) have been reported as blooming species. DMSP is produced intracellulary and it is released as DMS. DMS concentration is high during the growth of the cells, predation or senescence. The production of DMSP is...
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The role of microhabitats in spatio-temporal differentiation of freshwater algal assemblages
Pusztai, Martin ; Němcová, Yvonne (advisor) ; Kulichová, Jana (referee)
This thesis deals with microhabitats in relation to the spatio-temporal differentiation of freshwater algal assemblages. Algae are defined ecologically, althought they represent a diverse polyphyletic conglomerate. Based on the available literature, type of substrate appears as a suitable representative of most freshwater microhabitats when comparing results from different studies. Influence of microhabitat may occur not only on a small spatial scale, but also on a regional scale. The importance of scale and traceability of different factors are further discussed as well as the appropriate definition of the microhabitat. Microhabitats diversity is often reflected in the spatial heterogeneity of algal assemblages. Based on the common trends in the algal life strategies, erosional and depositional substrates can be distinguished. Living substrates, especially macrophyte surfaces represent a special category of microhabitats. Algae can enter complex interactions with these living substrates.Temporal dynamics is relatively less explored in comparison with the spatial heterogeneity.
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The Potential Use of the Eustigmatophyceae In the Production of Biofuels
Pilátová, Jana ; Němcová, Yvonne (advisor) ; Pichrtová, Martina (referee)
The eustigmatophytes - yellow-green microalgae - are well known for their high lipid content which is constituted by high amounts of essential polyunsaturated fatty acids (PUFA), such as eicosapentaenoic acid (EPA). This, combined with their high growth rate and an exceptionally high adaptability, makes them very promising feedstock for the biofuels production. In this bachelor thesis the role of eustigmatophytes in the production of biofuels is depicted with consideration of the issue of various cultivation conditions effects on the lipid content and composition. The first review of fatty acid distribution in eustigmatophytes ever reported is provided herein. Thus this work might be tentatively contributing to the strain selection issue - one of the most discussed topics in the biofuels field. The fatty acid distribution is qualitatively and quantitatively changed under various chemical and physical stress conditions. Thus the impact of nitrogen and phosphorous availability alongside with light intensity or temperature on lipid changes are presented. In addition, the process of fatty acid and polyunsaturated fatty acid synthesis is briefly outlined. Recent genetic engineering trends and successes are also mentioned, such as the implementation of high-efficiency homologous recombination to...
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Cold adaptation of snow algae: the role of changes in the composition of fatty acids
Dřízhalová, Marie ; Nedbalová, Linda (advisor) ; Němcová, Yvonne (referee)
Snow algae as typical extremophiles are good model organisms for study of adaptation for life on the boundary of physiological possibilities. So far, it is not clear, how these microorganisms ensure on the molecular level the optimization of photosynthetic processes in conditions around 0 řC, often with very high light intensity. The aim of this work was to find out light and temperature growth optima of two less studied strains and to assess the composition of fatty acids in selected psychrophilic and psychrotrophic strains from the genera Chloromonas and Chlamydomonas (Chlamydomonadales, Chlorophyta) from culture collections UTEX and CCCryo and collections in Europe including the Czech Republic and Slovakia. Using crossed gradients method, this thesis describes optimal temperature and light conditions of two strains of snow algae isolated from sites in the Krkonoše Mountains that are characterized by different ecological conditions. The strain Chloromonas reticulata Luční originates from alpine zone and according to its growth characteristics, it can be classified as psychrotrophic alga requiring high light. The second tested strain was Chloromonas pichinchae Meandry from forest environment, which is also characterized as psychrotrophic, In contrast to previous strain, it grows in a wide range of...
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Defence mechanisms of phytoplankton exposed to UV radiation
Dvořáková, Jana ; Němcová, Yvonne (advisor) ; Pichrtová, Martina (referee)
Phytoplankton builds an important part of energy flow in the Earth's ecosystem. It forms the basis of the food chain and represents main primary producers. The question arises, due to the continuing ozone depletion, what impact may cause the increasing intensity of UV radiation on aquatic ecosystems. Especially UV-B radiation is capable of penetrating depp into the water column and affects the key physiological processes (e.g. growth, reproduction) and causes acute physiological stress to aquatic organisms including phytoplankton. The gole of my thesis is to summarize the studies focused on the impact of UV radiation on planktonic algae and the defense mechanisms that reduce the negative effects of UV radiation. These mechanisms may be devided into three groups: active avoidance, production of UV-absorbing substances and repairs of damage induced by UV radiation. Powered by TCPDF (www.tcpdf.org)
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The significance of silica structures in chromist microorganisms.
Nováková, Dora ; Škaloud, Pavel (advisor) ; Němcová, Yvonne (referee)
The silica is one of the most common elements in the Earth's crust. During erosion it is released in soluble form to the environment, where some organisms can accumulate the silica and incorporate it to their bodies by biosilicification process. The organsims possessing this ability are widespread either when considering their position in eukaryotic tree of life, or their abundance in natural ecosystems. As a result, the whole global biogeochemical cycle of silica is controlled by biosilicificated organisms. In Chromista microorganisms, the silica is loaded to so-called "silica deposition vesicles" - membrane surrounded compartments, in which the silica is polymerated and formed into the final shape of silica structures during an ingeniously controlled in vivo process. Apparent differences in the process of silica deposition among Chromista microorganisms imply that this ability has developed independenty and repeatedly within the group. The most common silica structures are scales, bristles, cases, skeletons and cysts. The analogical structures often originated independently in unrelated lines of Chromista by means of convergent evolution. On the contrary, in some lineages of Chromista, the ability of biosilicification was suppressed. It is therefore very likely that the silica structures should...
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Vertical migration of benthic cyanobacteria and algae
Mensa, Jakub ; Neustupa, Jiří (advisor) ; Němcová, Yvonne (referee)
Vertical migration has been observed in different taxonomic groups of benthic microalgae and cyanobacteria in both marine and freshwater habitats. It seems to be an advantageous survival strategy of motile photoautotrophic organisms. In general, algae inhabiting tidal environments migrate up to the sediment surface during daytime emersion and then migrate below the surface prior to high tide or dusk. Freshwater microalgae stay on the surface during daytime and migrate below the surface before dusk. The migratory rhythm can be controlled or influenced by light, waves, subsurface nutrient supplies and reducing conditions in the sediment. Sometimes, the rhythm persists even in constant conditions and it seems to be controlled by biological clock system.
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Chrysophyte stomatocysts - encystation and excystation dynamics - bentic resting stages of chrysophytes
Mušálková, Petra ; Němcová, Yvonne (advisor) ; Juráň, Josef (referee)
The resting resistant stage has several important roles for phytoplankton microorganisms. It protects them from hostile conditions, allows them to spread to new locations and is often part of their life cycle. Chrysophytes form large populations for only a short part of the year, and therefore the formation of a resting stage is key for them to re-establish a vegetative population the following year. Chrysophyte resting stages are called stomatocysts, which are silicified and have a unique species-specific morphology. They can be form after both sexual and asexual reproduction. This is an understudied area. Most described stomatocysts are not assigned to species and much is not known about the triggers of encystation and excystation. It is thought that a combination of external (temperature, light, nutrients) and internal (cell age and cell concentration) factors are involved. So far, only sexual encystation in Dinobryon cyindricum and Synura petersenii has been studied in detail. My diploma thesis is based on laboratory experiments with Ochromonas tuberculata, Synura uvella and two strains of Synura petersenii. The aim of the study was to investigating whether external conditions such as temperature and lack of nitrogen or phosphorus have the effect on asexual encystation and whether it is...
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