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Methanogenic symbionts of Psalteriomonadidae (Heterolobosea: Tetramitia)
Foučková, Martina ; Čepička, Ivan (advisor) ; Steinová, Jana (referee)
Psalteriomonadidae is a small family of anaerobic amoeboflagellates belonging to Heterolobosea. So far, 16 species have been described and there are also at least another 17 putative species which are yet to be formally described. Their anaerobic lifestyle is associated with a modification of the mitochondria into hydrogen-producing hydrogenosomes. The main focus of this thesis is on methanogenic symbionts of this family. The presence of prokaryotic symbionts has been observed in three species of Psalteriomonas, namely P. lanterna, P. vulgaris and P. magna. In P. lanterna, and P. vulgaris the symbionts were identified as Methanobacterium formicicum on the basis of their morphology and biochemical properties. For this thesis, 37 new freshwater isolates of psalteriomonadids were collected, identified, sequenced, and together with older isolates in culture, were investigated for the presence of prokaryotic symbionts. The UV autofluorescence of the symbionts of P. lanterna P. magna and Psalteriomonadidae sp. 5 indicates that they are methanogenic Archaea. No traces of methanogens were found in three isolates of Sawyeria marylandensis and three isolates of different Harpagon species. The symbionts were identified as Methanoregula sp. based on the 16S rRNA gene sequence. The symbionts were divided into...
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Iron-sulphur cluster synthesis in anaerobic protists
Zelená, Marie ; Hampl, Vladimír (advisor) ; Mach, Jan (referee)
Iron-sulpur clusters are small ubiquitous cofactors of proteins present in all cells. These proteins participate in many important processes such as gene expression or respiratory chain. In vivo synthesis of iron-sulphur clusters requires complex biosynthetic pathways. In eukaryotic cells these pathways are localized inside mitochondria and plastids and in the cytosol. Cytosolic synthesis depends on a product of the mitochondrial pathway. Mitochondria of anaerobic protists in most cases went through reductive evolution, which is associated with the reduction of mitochondrial iron-sulphur cluster biosynthetic pathway. In many cases, these organisms acquired alternative pathways via lateral gene transfer, which act either as a complement to the mitochondrial pathway, or as its complete functional substitution. Replacement of the mitochondrial pathway might have been a key event for secondary loss of mitochondria. Key words: Iron-sulphur clusters, anaerobic protists, ISC, CIA, SUF, mitochondrion
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