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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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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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Impact of habitat type and long-term in vitro cultivation on photosynthetic characteristics of snow algae and their resistance to stress induced by UV radiation
Zázvorková, Michaela ; Nedbalová, Linda (advisor) ; Kvíderová, Jana (referee)
Snow algae are psychrophilic microorganisms, that inhabit snow fields in mountains and polar regions, which creates colored snow in good conditions. Most species belong to order Chlamydomonadales (Chlorophyta) with complicated life cycles, containing flagellates and immobile stages (cysts). Extreme environment of snow is characteristed by low temperature, problems with availability of water and lack of nutrition. Depending on location and phase of life cycle, snow algae have to deal with excess or lack of solar radiation, the important component of which is also dangerous UV radiation. The light conditions differ substantially from open location above the forest level or polar regions to forest habitats. In the first part of this work I compared reactions of photosynthetic apparatus of snow algae strains from forest and forestless habitats to different intensity of radiation, then I dealt with assessing any changes related to long-term cultivation in laboratory. Based on measurement of rapid light curves on PAM fluorometer I have determined some characteristics of photosynthetic apparatus of individual strains (parameters α and Ik), which indicate adaptation to low or high light intensity. For some strains, it was possible to compare the results obtained at a three-year interval. In the second part...
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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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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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Adaptation of algae to extreme environments
KVÍDEROVÁ, Jana
The acidophilic red alga Cyanidium sp. is one of the dominant mat-forming species in the highly acidic waters of Río Tinto, Spain. The culture of Cyanidium sp., isolated from a microbial mat sample collected at Río Tinto, was exposed to 9 different pH conditions in a gradient from 0.5 to 5 for 24 h and its physiological status evaluated by variable chlorophyll a fluorescence kinetics measurements. The optimum pH ranged from 1.5 to 2.5. A steep decrease of the photochemical activity was observed at pH below 1 even after 30 min of exposure. At pH above 2.5, the decline was more moderate and its negative effect on photochemistry was less severe. The red alga Cyanidium sp. is well-adapted to prevailing pH at its original locality at Río Tinto, i.e. pH of 1 to 3. The short-term survival in pH<1.5 may be adaptation to rare exposures to such low pH in the field. The tolerance of pH above 3 could be caused by adaptation to the microenvironment of the inner parts of microbial mats in which Cyanidium sp. usually dominates and where higher pH could occur due to photosynthetic oxygen production.
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