National Repository of Grey Literature 57 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Effect of stress factors on carotenoid production in isolated soil algae strains
Očadlíková, Terezie ; Němcová, Yvonne (advisor) ; Nedbalová, Linda (referee)
Microscopic green algae produce a number of beneficial substances. The commercially used ones include mainly pigments, especially secondary carotenoids. While primary carotenoids are part of the photosynthetic apparatus, secondary carotenoids are produced only under certain specific conditions (e.g. high exposure to light, nitrogen deficiency). Secondary carotenoids have antioxidant properties that protect the cell from adverse effects. The strains currently in commercial use and the strains that are tested for potential use come almost exclusively from algal collections, so this thesis focuses on strains isolated from nature. Two strains of aeroterrestrial green unicellular algae, which showed potential of producing carotenoids, were found and isolated. These strains were identified as Tetracystis pulchra (clade Dunaliellinia) and Tetracystis sp., a strain related to Tetracystis tetraspora SAG 98.80, belonging to the clade Stephanosphaerinia. The culture conditions for T. pulchra were subsequently optimized and then the culture was subjected to a series of experiments, examining the effect of stress factors on carotenoid formation and accumulation. Specifically, the effect of nitrogen starvation, light intensity, temperature and UVA radiation was tested. It has been shown that especially the light...
Green microalgae in polar lakes: diversity, biogeography and methodological comparison
Šamšulová, Tereza ; Nedbalová, Linda (advisor) ; Dvořák, Petr (referee)
In polar regions, green microalgae (Chlorophyta) are an important group of primary producers. However, little attention has been paid to them in comparison with other primary producers such as diatoms and cyanobacteria. The aim of this thesis was to describe the diversity of Chlorophyta in Arctic and Antarctic lakes, and to gain new insights into their taxonomic composition and biogeographic patterns. Microbial mat samples were collected from the littoral zones of 137 Arctic and Antarctic lakes from various regions (Svalbard, North Greenland, South Greenland, Antarctic Peninsula, and Continental Antarctica) during expeditions performed between 1993 and 2018. We combined Sanger sequencing of isolated strains and amplicon sequencing of environmental samples. The 18S rDNA and ITS2 rDNA regions were analysed using both molecular methods. In total, 65 laboratory cultures were established from Svalbard and Antarctic Peninsula samples. Sanger sequencing of strains revealed 15 taxa belonging to classes Chlorophyceae and Trebouxiophyceae. The most abundant were for instance Chlorella spp. and Micractinium spp. Amplicon sequencing of 18S rDNA yielded 202 OTUs in total, of which 61.4% of OTUs were present in both polar regions. The use of ITS2 rDNA revealed 1,104 OTUs in total, with 53.2% being present in...
Phytoplankton in acidified lakes: structure, function and response to ecosystem recovery
Nedbalová, Linda
This thesis is based on five publications dealing with plankton assemblages of lakes in two heavily acidified mountain areas in Central Europe, the Bohemian Forest and the High Tatra Mountains. As both lake districts are the object of long term systematic ecological research, a unique set of complex limnological data was gathered, enabling a comparison with other affected regions throughout the world and also some attempts at generalisation. My role in the team consisted chiefly in the study of phytoplankton as the key component of the food web. I was mainly concerned with the structure, seasonal development and function of the phytoplankton assemblages, and I also focused on the evaluation of general biological response to the current chemical recovery of the lakes from acidification. The main questions addressed in this thesis with an emphasis on phytoplankton assemblages are the following: What is the recent progress in chemical and biological recovery of the Bohemian Forest lakes from acidification? What are the key factors and mechanisms influencing species composition and structure of plankton biomass in the Bohemian Forest lakes? What is the role of episodic acidification in shaping both phytoplankton abundance and biomass in a non acidified high mountain seepage lake (Ľadové Lake, High Tatra...
Exploring the diversity of snow algae using polyphasic approach
Procházková, Lenka ; Nedbalová, Linda (advisor) ; Karsten, Ulf (referee) ; Hoham, Ronald (referee)
Snow algae cause blooms in slowly melting snowfields in mountain and polar regions. Although they are excellent models for the study of life in extremely cold environments, their taxonomical diversity, geographical distribution and variety of physiological strategies used to cope with their harsh environment are only partially understood. This work was focused on green algae from the order Chlamydomonadales and in one case on golden algae from the order Hibberdiales. An integrative approach was applied to characterise species, including the sequencing of several molecular markers (18S rDNA, ITS2 rDNA, rbcL) to reveal genotypes and infer phylogenetic positions. Light and electron microscopy were conducted to describe the detailed structure of cell wall surfaces and intracellular compartments. Moreover, fatty acid and pigment profiling were carried out to provide new insights into the adjustments of metabolic pathways in these algae. Rapid light curve measurements were used as a proxy of light preferences of photosystem II. Firstly, one of the main algae responsible for causing the phenomenon of red snow was shown to represent a single, monophyletic lineage, independent from other algae within the Chlamydomonadales (paper I). Therefore, the new genus Sanguina (S.) was described, with two...
Diversity of microalgae from extreme habitats: linking phylogeny and ecology
Barcyte, Dovile ; Nedbalová, Linda (advisor) ; Dvořák, Petr (referee) ; Bock, Christina (referee)
The diversity of microalgae from extreme habitats is far from being fully explored and understood. This is due, in part, to limited sampling efforts along with complex algal taxonomy and systematics. In particular, little investigated extremely acidic (pH < 3.0) and polar habitats might veil novel, undescribed species. This doctoral thesis aimed to study algal strains isolated from acidic or acidic and hot, and cold environments using a polyphasic approach. It focused on coccoid (Coccomyxa and Watanabea), monadoid (Chloromonas and its relatives) and saccoderm (Cylindrocystis) green microalgae from the classes Trebouxiophyceae, Chlorophyceae, and Zygnematophyceae, respectively. In addition, coccoid red algae (Galdieria) from the class Cyanidiophyceae were covered. The main research methods included light and transmission electron microscopy combined with Sanger sequencing. Nuclear 18S rDNA and plastid rbcL sequences were used for construction of phylogenetic trees for taxonomic position evaluation. Comparisons of secondary structure models of the highly variable ITS2 rDNA molecular marker served for a more detailed genetic relationship estimation among close relatives. Results have shown that Coccomyxa and Watanabea are present in extremely acidic lakes and that acidity and increased availability of...
Biodiversity-productivity relationship in desmid communities
Škvorová, Marie ; Škaloud, Pavel (advisor) ; Nedbalová, Linda (referee)
This thesis deals with biodiversity-productivity relationship in desmid communities. Biodiversity is found to be changing globally. The biodiversity-productivity relationship is therefore an important research topic. Three aspects of biodiversity are thought to play an important role: species richness, functional diversity and phylogenetic diversity. It is known that in general, productivity is positively correlated with diversity. Interactions between different metrics of biodiversity are known less. Existing studies have shown that these interactions might be present. In general, biodiversity-productivity studies were mostly focused on plants. Less is known about other organisms, including algae. In this work I explore the relationship between overyielding and functional or phylogenetic diversity on a species richness gradient of desmid communities. I conducted an artificial biodiversity- ecosystem functioning experiment using combinations of two to 12 desmid species. Communities differed in the diversity aspects. I had measured the biomass growth. For the analysis, I have used the overyielding index, which is based on a comparison of a polyculture production with the production expected based on monoculture yields. The relationship of overyielding on functional diversity depended on species...
Impact of habitat type and long-term in vitro cultivation on photosynthetic characteristics of snow algae and their resistance to stress induced by UV radiation
Zázvorková, Michaela ; Nedbalová, Linda (advisor) ; Kvíderová, Jana (referee)
Snow algae are psychrophilic microorganisms, that inhabit snow fields in mountains and polar regions, which creates colored snow in good conditions. Most species belong to order Chlamydomonadales (Chlorophyta) with complicated life cycles, containing flagellates and immobile stages (cysts). Extreme environment of snow is characteristed by low temperature, problems with availability of water and lack of nutrition. Depending on location and phase of life cycle, snow algae have to deal with excess or lack of solar radiation, the important component of which is also dangerous UV radiation. The light conditions differ substantially from open location above the forest level or polar regions to forest habitats. In the first part of this work I compared reactions of photosynthetic apparatus of snow algae strains from forest and forestless habitats to different intensity of radiation, then I dealt with assessing any changes related to long-term cultivation in laboratory. Based on measurement of rapid light curves on PAM fluorometer I have determined some characteristics of photosynthetic apparatus of individual strains (parameters α and Ik), which indicate adaptation to low or high light intensity. For some strains, it was possible to compare the results obtained at a three-year interval. In the second part...
Ecological and taxonomic structure of subaerial biofilms of green algae on the needles of gymnospermous trees
Zelená, Radka ; Neustupa, Jiří (advisor) ; Nedbalová, Linda (referee)
Aero-terrestrial algae form distinct biofilms on different natural and man-made surfaces. Their taxonomic diversity is considerable, but not yet fully studied, even though recent attention has been paid to it. The study of the diversity of these algae is made more difficult by the morphological convergence of representatives of the most common class of Trebouxiophyceae, who most often form coccoid thalli. That is why molecular genetic methods are very often applied to study these algae. In addition to species diversity, the ecology of these algae communities, their spatial diversity, seasonality are also studied. In my work I focused on two aspects of microbial biofilms growing on the needles of the common yew. In the first study, I evaluated the amount of algae in biofilms on needles within the Prague urban ecosystem in relation to the air quality. This is the first study of this type on a small scale, showing that these biofilms could serve as bioindicators of air quality in urban areas, reflecting different concentrations of nitrogen oxides and particulate matter. In my second study I studied the taxonomic diversity of these biofilms in two European regions. So far no taxonomic study has been made from this specific habitat. We have recorded a relatively large amount of algal taxa despite the...
Freshwater green algae in polar regions: diversity, biogeography and methodology comparison
Šamšulová, Tereza ; Nedbalová, Linda (advisor) ; Chattová, Barbora (referee)
Green algae (Chlorophyta) are an important group of primary producers in polar regions, but they received less attention in comparison with cyanobacteria and diatoms. Environmental conditions of freshwater habitats in the Arctic and Antarctica (lakes, wetlands, streams, glaciers and snow) are very variable and microoganisms have to resist multiple extreme conditions. The overview of 58 green algal genera from polar regions showed the prevalence of representatives from the Chlorophyceae and Trebouxiophyceae, more genera were documented from the Arctic. Lakes have the highest and wetlands the lowest genus richness. This fact could be affected by uneven number of studies in both polar regions and from different habitats. The occurrence of several species has been documented only in Antarctica, but overall the green algae distribution is supposed to be rather ubiquitous. The traditional method of biodiversity research is light microscopy, which has limitations due to simple morphology of green algae. Their identificatiton at genus or species level is thus often possible only using molecular methods. While sequencing by Sanger method is used for determination of monospecific isolates, metagenome analysis allows the identification of non-cultivable or rare species. The use of combination of methods...

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