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Life cycle of Haematococcus pluvialis (Chlorophyceae) species complex
Vávrová, Karolína ; Němcová, Yvonne (advisor) ; Nedbalová, Linda (referee)
Freshwater green algae within species complex Haematococcus pluvialis are best natural producers of secondary carotenoid astaxanthin famous for its strong antioxidant activity. Despite worldwide distribution, great biotechnological potential and extensive literature dealing with different approaches to the cultivation of these organisms, there still remains surprising gaps in knowledge of their complex life cycle and behaviour. First uncertainty concerns asexual cell division of zoospores, hypothetically limited to five cell doublings (Lee & Ding 1994). No such genetic limitation was observed in this thesis, number of cell divisions is thus influenced mainly by cultivation conditions. There is still considerable uncertainty regarding to the asexual reproduction, as well. Ambiguity might be caused by scarce observation of the whole process of gametogenesis and conjugation of gametes. Published studies differed in some particular points. Unfortunately, we did not succeed in induction of gametogenesis despite broad scale of tested cultivation conditions applied to two different species within the H. pluvialis complex, namely H. pluvialis and H. rubicundus. This failure might be caused by heterothalism of the studied strains. Haematococcus pluvialis inhabits mainly ephemeral pools. Its ability to...
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Adaptive functions of algal resting stages with emphasis on the chrysophyte stomatocysts
Mušálková, Petra ; Němcová, Yvonne (advisor) ; Pusztai, Martin (referee)
Formation of resting stages is a very common feature occurring in most algae classes. Primarily this stage is considered as a resistant form that helps the organism to survive adverse conditions and rapidly changing environment. However, it may also serve to spread as a seed bank to recolonize habitat or can be a source of genetic variation if it follows sexual reproduction. The importance of this dormant benthic stage grows with algae whose population growth is seasonal and the formation of cysts or spores is crucial for them, for instance dinoflagellates and golden algae. Resting stages of Chrysophyceae are called stomatocysts they are produced endogenously and are composed of polymerized silica. Stomatocysts have species-specific morphology. For most described species of Chrysophyceae morphology of the stomatocyst is unknown. Determining the species is difficult especially because of rapid alternation of chrysophyte dominant species in natural waterbodies. So far, it has not been elucidated what factors cause encystation and excystation. Several laboratory experiments has been conducted on this subject. The process of encystation and excystation is assumed to be induced by combination of external and internal factors. Stomatocysts may developed after sexual reproduction or from vegetative cells....
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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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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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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 like typical extermofils are ideal model organisms for study of adaptation for life on the boundary of physiological possibilities. So far, it is not clear how these psychrophilic organisms on the molecular level optimize function of photosynthetic processes in temperatures about 0řC and often in very high radiation. This thesis evaluates growth limits and monitors the composition of fatty acids in selected subclade of psychrophilic and psychrotrophic algae of mainly the Chlamydomonadaceae (Chlorophyta) class isolated from localities in European area (as received from Culture collections UTEX and CCCryo), including the subclade from Czech republic and Slovakia. I found out optimal conditions of growth using cultivation in crossed gradients (temperature/irradiance) for two subclades snow algae. In Chloromonas reticulata Luční (red snow), there is 8-20řC growth optimum and optimal irradiation exceeds 423 µmol.m-2 .s- 1 . I classified this alga as psychrophilic. The second tested alga was Chloromonas pichinchae Meandry. Optimal temperature of growth is in interval 4-10řC. Maximal temperature does not exceed 30řC and in this experiment it is the second psychrophilic algae found in area of the Czech republic. This discovery should be checked and data on growth in temperaturees between 9-20řC...
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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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Applications of diatom and chrysophyte silica structures in nanotechnologies
Burýšková, Barbora ; Němcová, Yvonne (advisor) ; Urbánková, Pavla (referee)
Diatoms and chrysophytes are single-celled organisms who have mastered the ability of controlling the biomineralization process. By incorporating silicon into their cell walls diatoms are able to create elaborate 3D silica structures with hierarchically ordered patterns and pores at the nano- to millimetre scale. In nature, diatoms inhabit almost all aqutic and aeroterrestrial environments. They play an important role in the global biogeochemichal silicon cycle and contribute significantly to oceanic primary production. The morphology of diatom cell walls (frustules) is species specific and the frustules exhibit unique photonic, optical and mechanical properties. There are more than 12 000 diatom species on earth, which represents the vast diversity of silica frustule shapes, applicable in nanotechnologies. However, only a few species have been used in experimental praxis so far. The cells of silicifying chrysophytes are covered with scales composed of the same material as the diatom frustules. The potentional use of chrysophyte silica scales in nanotechnologies is in the early stages of investigation. The aim of this bachelor's thesis is to recapitulate the findings on diatom and chrysophyte silica structures use in emerging nanotechnology applications, and to summarize published information on...
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Stress resistance of polar hydro-terrestrial algae Zygnema spp. (Zygnematophyceae, Streptophyta)
Pichrtová, Martina ; Němcová, Yvonne (advisor) ; Nedbalová, Linda (referee) ; Karsten, Ulf (referee)
Filamentous green microalgae of the genus Zygnema belong to the most common primary producers in the polar hydro-terrestrial environment. In such unstable habitats, organisms are subject to various stress factors, e.g., freeze-thaw cycles, desiccation and high irradiation levels. However, the stress resistance mechanisms that enable Zygnema spp. to thrive in this extreme environment are only partially understood. Therefore, polar Zygnema spp. were examined under various stress conditions using both field samples and cultures. Moreover, molecular phylogeny methods were applied that provided first insights into the diversity of polar Zygnema. Sequencing of the chloroplast gene rbcL revealed several different Zygnema genotypes and, surprisingly, one Zygnemopsis sp. with vegetative Zygnema sp. morphology. First set of experiments examined the effects of UV exposure. It turned out that polar strains of Zygnema produce phenolic substances as UV screens. These substances are most likely stored in vacuoles and other vesicles at the cell periphery, providing protection for other organelles. In the next study, Zygnema spp. were investigated under natural conditions in the Arctic. At the end of summer, the cells gradually lose their typical vegetative appearance (with large vacuoles and stellate chloroplasts)...
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The role of microhabitats in spatio-temporal differentiation of phytoplankton flagellates
Pusztai, Martin ; Němcová, Yvonne (advisor) ; Bílý, Michal (referee)
This thesis deals with factors structuring phytoplankton flagellates. The aim of the thesis was to investigate the role of microhabitats in spatio-temporal differentiation of lentic communities of these flagellates, which has not been rigorously examined to date. The study was conducted during 2010-2013 in the shallow littoral sites of Horní rybník, Rybníčky u Podbořánek Nature Reserve. Phytoplankton flagellates showed cyclic seasonal dynamics, which was reflected by significantly different community structure and species richness during the season. In contrast, silica-scaled chrysophytes showed a non- cyclic seasonal dynamics. The impact of the season was strongly correlated with the impact of fluctuating environmental factors - pH, conductivity and temperature. Gradient of interrelated environmental factors between the northern and southern shore together with microhabitat - substrate type played the major role and accounted for 64.4 - 75.8 % variability in the data. Microhabitat type (plankton, metaphyton, epipelon) significantly affected species richness and community structure also in the course of the season. A large number of species was assessed to prefer a certain type of microhabitat. These preferences were observed at both species and generic levels, and even at the level of the main taxonomic...
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Cell cycle of astaxanthin producing green alga Haematococcus pluvialis, culture media and cultivation conditions
Vávrová, Karolína ; Němcová, Yvonne (advisor) ; Pichrtová, Martina (referee)
Haematococcus pluvialis is unicellular green alga (Chlorophyceae, Chlamydomonadales), which can be found in ephemeral rock pools and birdbaths. It is the best natural producer of strong antioxidant astaxanthin, red secondary carotenoid used as coloring agent in aquaculture and poultry breeding. Astaxanthin also has various positive effects on human health. Haematococcus pluvialis has quite complex life cycle consisting of four life stages, biflagellated zoospores, non- motile round palmella stage, thick-walled akinetes (aplanospores, cysts) with high content of astaxanthin and small biflagellated gametes. Akinetes, which enable H. pluvialis to survive desiccation in its natural habitat, are formed in response to stress conditions such as high irradiance and temperature and nutrient depletion. Cells undergo dramatic ultrastructural changes during aplanospore formation. Chloroplast volume is decreased, synthesis of high amount of astaxanthin and fatty acids results in presence of lipid droplets that spread from the center to the periphery of the cell and thick cell wall containing algaenans is formed. Cultivation of H. pluvialis is often performed in two subsequent stages, green stage focused on biomass production and red stage focused on astaxanthin accumulation under stress conditions. There are...
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