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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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Taxonomy, ecology and biogeography of aquatic and limno-terrestrial diatoms (Bacillariophyta) in the Maritime Antartic Region
Kopalová, Kateřina ; Nedbalová, Linda (advisor) ; Sabbe, Koen (referee) ; Jüttner, Ingrid (referee)
Diatoms (Bacillariophyta) are one of the most diverse algal groups in the Antarctic Region and play a dominant role in almost all freshwater and terrestrial ecosystems. Despite this overall occurrence, little is known about the diversity, ecology and biogeography of this group in the Maritime Antarctic Region. The main objective of this thesis is therefore to define the taxonomical, ecological and biogeographical characterisation of aquatic, semi- aquatic and moss-inhabiting diatom communities from two islands in the Maritime Antarctic Region: James Ross Island and Livingston Island, located on opposite sides of the Antarctic Peninsula. In this study, a total of 250 samples from three different habitat types (lakes, streams & seepage areas and mosses) from Byers Peninsula (Livingston Island) and Ulu Peninsula (James Ross Island) have been analysed. Using light and scanning electron microscopy, a rather diverse diatom flora composed of 178 taxa, belonging to 43 genera has been identified. Although even until recently, it was generally accepted that the Antarctic diatom flora was mostly composed of cosmopolitan taxa, several new species could be described as a new for science during this PhD study (a reflection of this work is presented in chapters 2 & 3 and in Appendices). Habitat type and...
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Diversity, ecology and ecophysiology of snow algae
Mikešová, Lenka ; Nedbalová, Linda (advisor) ; Kvíderová, Jana (referee)
Permanent and temporary snow cover in polar and mountain areas is a very extreme habitat. However, there are organisms that inhabit this environment. Green algae of the order Chlamydomonadales (Chlorophyta) belong among the important representatives of cryoseston, which are known from polar and mountain regions around the world. These organisms, which occupied the snow environment probably secondarily, developed different ecophysiological adaptations required for the successful survival in extreme conditions. Low temperatures and high levels of radiation are the main extreme factors that organisms must cope with. The most important survival mechanisms include the adaptation of life cycles (such as of the shifts between resistant stages and moving vegetative stages), accumulation of secondary carotenoids, changes in fatty acid composition of membranes and lowering of growth temperature optima in some species. These adaptations together with the study of diversity represent at present the main subjects of research of snow algae.
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Acidophilous cyanobacteria and algae
Macholdová, Markéta ; Nedbalová, Linda (advisor) ; Medová, Hana (referee)
Due to natural processes and human activity extremely acidic habitats, whose pH does not exceed 3.0, are formed on Earth. These are especially areas affected by the acid mine drainage (AMD) and of volcanic activity. The biodiversity of these habitats is greatly reduced, but there are microorganisms that are very well adapted to such extreme conditions. These organisms are termed as acidophilic. Cyanobacteria and algae are the only primary producers at extremely acidic sites and thus play a crucial role in these ecosystems. Although they must overcome several problems that are associated with such an environment (excess of H+ ions, increased concentrations of heavy metals), they developed a range of ecophysiological adaptations and life strategies that allow them to inhabit it. These are mainly the ultrastructural changes in the cell membranes, special metabolic processes and the production of special substances and enzymes. Acidophilic species are present across almost all taxonomic groups of cyanobacteria and algae. Interest in acidophilic organisms has increased in recent decades due to their potential use in biotechnology. Knowledge of their taxonomy, ecology and ecophysiology can also be used in paleobiology and exobiology.
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Phytoplankton succession in experimental ponds
Zelený, Jakub ; Nedbalová, Linda (advisor) ; Bílý, Michal (referee)
1 Abstract Newly created habitats present a unique model environment for the study of succession and related processes. Their relative isolation and the possibility to observe community assembly dynamics from the very beginning makes these experiments repeatable under controlled conditions. Planktic organisms with short generation cycles represent useful model organisms for the research of succession and related features like the influence of environmental variables or priority effect. The thesis aims at describing the succession of phytoplankton in a set of 20 experimental ponds, where phytoplankton structure and environmental parameters have been observed for six years (2007 ̶ 2012). The ponds are located in Liběchovka River-bed, which is a part of Kokořínsko Protected Landscape Area. The target locality is protected by the Ramsar agreement as a habitat for pulling birds and amphibians. We used classical and multidimensional statistical methods (PCA, DCA, CCA) to analyse the variability in species composition and shifts in environmental variables. Metacomunity structure indices (α,ß,γ) showed a decrease of α diversity accompanied by an increase in ß diversity over the study period, which have been caused by a marked differentiation of communities in 2011 ̶ 2012. γ diversity peaked in the middle of the...
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Dispersal mechanisms in freshwater algae and cyanobacteria
Hejduková, Eva ; Nedbalová, Linda (advisor) ; Pichrtová, Martina (referee)
Global occurrence of many species of freshwater cyanobacteria and algae shows, that they are dispersed easily. However, the exact transport mechanisms are not known for most of these microorganisms. This bachelor thesis introduces various mechanisms that could be responsible for the dispersal of freshwater cyanobacteria and algae. It includes information about four main methods of transport, which is dispersal by water (hydrochory), transport through atmospheric circulation and wind (anemochory), dispersal by animals (zoochory) and by human (anthropochory), who is recently also involved in the transportation of freshwater cyanobacteria and algae. The thesis also summarizes adaptation mechanisms that enable cyanobacteria and algae to colonize new habitats successfully, and discusses possible implications of the dispersal ability for the distribution of microorganisms. Currently there are two contradictory views - cosmopolitan distribution and the occurrence of endemic species. Despite their importance the dispersal mechanisms of freshwater cyanobacteria and algae are less-studied than it might seem at first sight. Key words: freshwater algae, cyanobacteria, dispersal mechanisms, spores, cysts, distribution of microorganisms, hydrochory, anemochory, zoochory, anthropochory
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Extreme abiotic conditions as determinants of phytoplankton structure in high mountain lakes
Mihál, Martin ; Nedbalová, Linda (advisor) ; Hořická, Zuzana (referee)
There are many areas with extreme environmental conditions in the world. One of them are high mountain lakes which are located above treeline. Bachelor thesis presents the main abiotic conditions as determinants of phytoplankton structure in high mountain lakes. It has to cope with significant changes in light conditions and high intensity of sunlight during ice-free periods and with an important diminution of radiation by snow and ice cover. The thesis also discusses the influence of temperature, which is related to the duration of the ice and snow cover and a stratification of lakes. It characterizes local factors, such as topographic shading, morphology of lakes and character of basins, which affect chemical and physical properties of lakes. The thesis also mentions the impact of atmospheric deposition and other factors on nutrient concentrations in the water column. In addition, it discusses the adaptations of phytoplankton to environmental conditions, which include development of deep chlorophyll maximum, biosynthesis of protective compounds and nutrition strategy (mixotrophy). The thesis shows that there are many specific abiotic factors, which influence phytoplankton in high mountain lakes and all these factors interact. This results in a characteristic species composition with prevalence of...
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Cold adaptation mechanisms in microorganisms
Dřízhalová, Marie ; Nedbalová, Linda (advisor) ; Kvíderová, Jana (referee)
On our planet there are vast areas, where the average temperature does not exceed 5 řC. They are also many places, where the temperature often drops below zero. Not every living organism is able to live in these conditions. The ability to survive in cold region and succefully colonize, such presumably adverse environment requires particular evolutionary adaptation. Adaptation to cold environments has evolved independently in different phylogenetic groups. In low temperature environments, organisms has to adapt in a complex way to be able to permanently inhabit these habitats. Since the analysis of cold adaptation in all organisms is a very complex topic, this thesis is focused on microorganisms. Within this group, it is possible to find certain, which are repeated also in unrelated taxa. The general mechanisms include changes in membrane composition, shifts of enzyme temperature optima, production of compounds that prevent the negative effects of low temperature or the formation of resting stages. This thesis summarizes the mechanisms of cold adaptation which have evolved in microorganisms as response to a long-term or temporary survival at low temperatures. Their potential biotechnological applications are also mentioned. keywords: psychrophilic, psychrotolerant, cold adaptation, enzymes,...
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