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Evolution of nuclear DNA content variation in the genus Mallomonas and its ecophysiological consequences
Čížková, Natálie ; Čertnerová, Dora (advisor) ; Trávníček, Pavel (referee)
The variability of genome size among eukaryotes and its consequences remains largely unknown. This is particularly true for unicellular eukaryotic organisms, also known as protists, whose nuclear DNA content is still largely unexplored. Across plants or animal studies, it has been repeatedly demonstrated that genome size is closely associated with cell size and may also be related to other eco-physiological parameters, such as growth rate, metabolic rate, or life strategy. In protists, the cell represents their entire body, allowing for the direct assessment of the impact of genome size on organismal phenotypic traits. In this thesis, with the use of flow cytometry, the absolute amount of nuclear DNA was estimated for 165 strains of the genus Mallomonas (Chrysophyceae) belonging to 64 species, revealing diversity in nuclear DNA content for nearly 1/4 of the globally recognized diversity of this genus. Based on the obtained data, up to 100-fold variability in nuclear DNA content was found across Mallomonas species (0.12 pg - 11.4 pg). Detected intraspecific variability in nuclear DNA content suggests the influence of various evolutionary mechanisms, for example multiple-fold difference in DNA content (even within closely related species) suggest frequent polyploidization in the genus Mallomonas....
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Temporal changes in the genetic and morphological diversity of silica-scaled chrysomonads (Stramenopiles, Chrysophyceae)
Tučková, Kateřina ; Škaloud, Pavel (advisor) ; Nedbalová, Linda (referee)
Temporal dynamics on short time scales is a very interesting area of research. Usually, temporal studies are done on a scale of months or years. However, microorganisms have a much shorter generation time and therefore changes can take place on a much smaller time scales. At the same time, almost none of the temporal studies go to the species level and mostly stay at the class level. That species dynamics change within days we know from observation, but this has never been properly verified. The genera Mallomonas and Synura from the class Chrysophyceae were chosen to study short-term temporal changes These two genera are characterized by the formation of siliceous scales on the surface of their cells, by which they are well morphologically identifiable to the species level. However, since species identification by microscopy is an old but traditional method, a new molecular method for species identification at the locality, i.e. metabarcoding, was also used. These two methods have been shown similar results for describing the golden algae community. At the same time, it was confirmed that temporal dynamics occur at the species level, but also at the section level in the genus Synura. Subsequently, it was possible to relate the environmental factors that cause temporal changes in the community to...
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Pattern as a functional trait, case study on Mallomonas chrysophytes
Knotek, Petr ; Němcová, Yvonne (advisor) ; Rychtecký, Pavel (referee)
The patterns that can be admired on the surface of many living creatures are also found in many microscopic organisms outside of the macroscopic world we are familiar with. However, their significance and function are yet little understood compared to those of the macroscopic world. In diatoms (Bacillariophyceae) and coccoliths (Haptophyceae), several hypotheses have already been developed concerning the function of their patterned shells. One hypothesis considers the shell as a photonic entity that could reflect UV radiation away from the cell. Others focus more on its mechanical properties, which are among the most impressive within biological structures. Silica-scaled chrysophytes (Synurales, Stramenopiles) also possess a complex shell (or scale-case). Cells are covered with scales (about 4 µm in size) that are very regularly arranged and form a siliceous scale-case on the surface. The pattern on the scales is species-specific and has undergone gradual modification during evolution. This work aims to assess whether the patterning of siliceous scales in the order Synurales can be considered a functional trait or it is a result of neutral evolution. To test the possible photonic properties of the patterned structures, a pair of growth experiments were performed. The experimental cultures were...
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