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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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Adaptive functions of algal resting stages with emphasis on the chrysophyte stomatocysts
Mušálková, Petra ; Němcová, Yvonne (advisor) ; Pusztai, Martin (referee)
Formation of resting stages is a very common feature occurring in most algae classes. Primarily this stage is considered as a resistant form that helps the organism to survive adverse conditions and rapidly changing environment. However, it may also serve to spread as a seed bank to recolonize habitat or can be a source of genetic variation if it follows sexual reproduction. The importance of this dormant benthic stage grows with algae whose population growth is seasonal and the formation of cysts or spores is crucial for them, for instance dinoflagellates and golden algae. Resting stages of Chrysophyceae are called stomatocysts they are produced endogenously and are composed of polymerized silica. Stomatocysts have species-specific morphology. For most described species of Chrysophyceae morphology of the stomatocyst is unknown. Determining the species is difficult especially because of rapid alternation of chrysophyte dominant species in natural waterbodies. So far, it has not been elucidated what factors cause encystation and excystation. Several laboratory experiments has been conducted on this subject. The process of encystation and excystation is assumed to be induced by combination of external and internal factors. Stomatocysts may developed after sexual reproduction or from vegetative cells....
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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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