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Diversity and phylogeny of Archamoebae
Zadrobílková, Eliška ; Čepička, Ivan (advisor) ; Kostka, Martin (referee) ; Bardůnek Valigurová, Andrea (referee)
Members of the group Archamoebae are free-living or endobiotic amoeboid flagellates and amoebae. They live in anoxic or microoxic habitats, and their mitochondria have been reduced. They were originally thought to lack mitochondria and represent one of the earliest eukaryotes. However, this hypothesis has been refuted, and now it is evident that the Archamoebae belongs to the lineage Conosa within the supergroup Amoebozoa, together with aerobic slime molds (Macromycetozoa) and variosean amoebae and flagellates. Relatively simple microtubular cytoskeleton is a characteristic feature of Archamoebae. It consists of a single basal body from which a flagellum arises, lateral root, and microtubular cone. Cytoskeleton of aflagellated genera has been completely reduced. About 350 species names of Archamoebae have been created so far. However, most descriptions were based on inadequate morphological features. The identity of numerous species is uncertain, and many of them are likely synonymous. Another problem is a small amount of available molecular data. During our project, we have substantially improved the dataset of DNA sequences of archamoebae. On the basis of molecular and morphological data, we described 13 new species. We showed that genus Rhizomastix belongs to Archamoebae and displays a new type...
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Morphological and molecular diversity of endobiotic and free-living trichomonads
Céza, Vít ; Čepička, Ivan (advisor) ; Bardůnek Valigurová, Andrea (referee) ; Fiala, Ivan (referee)
This PhD thesis presents the results of three subprojects focused on the research of so far understudied groups of the phylum Parabasalia. The previous research mostly focused on the parabasalids living in the guts of termites or on demonstrably pathogenic species. Surprisingly, there is only a little information about the impact of an increased contact of non-human primates with humans on the diversity of their intestinal trichomonads. Similarly, free-living trichomonads have been neglected for a long time, although they are likely crucial for understanding the evolution of Parabasalia as a whole. The diversity of the phylum Parabasalia is still poorly understood due to the brief and incomplete descriptions of many species, as well as a lot of missing sequence data. This doctoral project focused on the research of these hitherto understudied research areas. In the first subproject, a complete revision of the genus Hypotrichomonas was carried out, including the descriptions of six new species, some of which were found in previously well studied vertebrate hosts; these species must have been overlooked by the previous authors and the real diversity of intestinal trichomonads is certainly much higher than currently known. Because the most newly described species of Hypotrichomonas are readily...
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Diversity and phylogeny of Archamoebae
Zadrobílková, Eliška ; Čepička, Ivan (advisor) ; Kostka, Martin (referee) ; Valigurová, Andrea (referee)
Members of the group Archamoebae are free-living or endobiotic amoeboid flagellates and amoebae. They live in anoxic or microoxic habitats, and their mitochondria have been reduced. They were originally thought to lack mitochondria and represent one of the earliest eukaryotes. However, this hypothesis has been refuted, and now it is evident that the Archamoebae belongs to the lineage Conosa within the supergroup Amoebozoa, together with aerobic slime molds (Macromycetozoa) and variosean amoebae and flagellates. Relatively simple microtubular cytoskeleton is a characteristic feature of Archamoebae. It consists of a single basal body from which a flagellum arises, lateral root, and microtubular cone. Cytoskeleton of aflagellated genera has been completely reduced. About 350 species names of Archamoebae have been created so far. However, most descriptions were based on inadequate morphological features. The identity of numerous species is uncertain, and many of them are likely synonymous. Another problem is a small amount of available molecular data. During our project, we have substantially improved the dataset of DNA sequences of archamoebae. On the basis of molecular and morphological data, we described 13 new species. We showed that genus Rhizomastix belongs to Archamoebae and displays a new type...
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Freeze-fracture technique and artefacts caused by processing conditions
Vaškovicová, Naděžda ; Valigurová, A. ; Hodová, I. ; Melicherová, J. ; Krzyžánek, Vladislav
Freeze-fracture technique is a method used to visualise membrane surfaces of cell organelles. This method is based on cryo-fixation that stabilizes samples. The sample is rapidly frozen in nitrogen, and cut in the chamber under a vacuum and low temperature. Glycerol is used as a cryoprotectant preserving the fine structure of cells in their native stage. Although, cryoprotectants serve as a substitute for water and protect against ice crystal production, they could also affect the form of fracture through biological membranes. Figure 1 shows structures in a sample frozen in the presence of 25% glycerol. The temperature of the apparatus was not low enough during the process of fracturing and etching the sample. The structure of cells seems to be deformed due to melting glycerol. In contrast, figure 2 shows a replica with fine structure of frozen and proper good form of fracturing. The cells used for this study were human leukemic cells (HL-60). Another artefact is shown in figure 3A, compare with 3B. Each sample has to be fractured with a specific speed of cut. The force used for fracturing the membranes has to be set to optimal conditions, which depend on a hardness of sample and a coherence of drops. Low speed and unstable coherence of drops resulted in sample fragmentation. High speed of cut could cause cross-section of cellular structures, similar to ultrathin sections. Figure 3A shows fragmentation of nuclear membrane. This sample was not fractured, it was fragmented due to unstable coherence of drop. This overview shows how a combination of different conditions including the physical properties of the sample, cryoprotectants used and temperature could affect the form of fractures and hence significantly affect interpretation of morphological structures.
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