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The role of electroactive organisms in biomineralization reactions involving transition metals, nitrogen and humic substances under suboxic/anoxic conditions
VALERO, Astolfo
Electroactive microorganisms sustain their respiratory metabolisms by retrieving or transferring electrons to extracellular conductive particles. Electroactive metabolisms based on iron respiration can trigger the precipitation of Fe(III)-oxyhydroxides or changes in their crystallinity. Iron biomineralization has a sound effect on the geochemical cycles of elements because it also influence the solubility of other elements such as phosphorus and arsenic. Thus, siderophile elements are removed from solution within precipitated particles or they are released back after mineral stabilization. However, major insights are often deduced by studying lab isolates of model microorganisms and using simplified substrates. This does not reflect environments where the presence of redox stratification boosts the overlapping of nitrogen- and iron-based metabolisms and interspecies interactions regarding thermodynamics constraints of minimal energetic loss for microbial respiration. For example, reactive nitrogen species (i.e., nitrate and ammonia) serve as alternative electron sources as sinks during iron biomineralization in nature. This can be also furthered by the presence of re-oxidable moieties of humic substances, which are used as electron shuttlers to reach extracellular materials. Therefore, this doctoral research aimed to describe how the availability of redox-reactive humic substances and reactive nitrogen species, as alternative electron donors or acceptors, affect electroactive metabolisms and linked iron biomineralization in the anoxic water column of a redox-stratified lake with high metal load (Lake Medard, NW Czech Republic). This was addressed by assessing the geochemical and hydrobiological features of the uppermost layers of sediment and the redox-stratified ferruginous water column of Lake Medard, and then, (ii) using the resulting dataset as input conditions in bioelectrochemical experiments to model the lake's biomineralization reactions by inducing microbe-mineral interactions under controlled electric potentials.
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Microbial ecology of Alpine and High Arctic soils in changing climate
LULÁKOVÁ, Petra
This study has contributed to a deeper understanding of certain aspects of initial soil development in the extreme environments of the High Arctic and the High Alpine regions. Specifically, we have examined the impact of geochemistry on the initial microbial succession following deglaciation and its subsequent transition toward the predominant influence of pioneer plants over time and the process of SOC stabilization. Our focus has been on understanding substrate-microbial and plant-microbial interactions, particularly with regards to nutrient availability and stoichiometry. In addition to investigations carried out in the High Arctic regions, we conducted an incubation experiment in the High Alps. This experiment aimed to explore nutrient availability for microorganisms in relation to their response to varying high temperatures, which are observed under ongoing climate change.
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Changes of biogeochemistry in headwater areas. Aplication in experimental upper Rolava River basin.
Kočárková, Tereza ; Matoušková, Milada (advisor) ; Kujanová, Kateřina (referee)
The present bachelor thesis discusses biochemistry changes in headwater areas. The main object of the thesis is to analyze the hydro-climate factors of selected parameters of water quality monitoring in order to detect their trends and interconnections. In the first part of the thesis the literature research of the topic is presented. A short characterization of the area follows as well as the crucial gathered input data, homogenization and the data files analysis. The study is the interdependence of selected biogeochemical parameters and changes in rainfall-runnof. I have conducted my own monitoring of the selected parameters of water quality. The experimental upper Rolava River basin is located in the northwest part of the Ore Mountains in the Czech Republic. Key words: Biogeochemistry, pH, conductivity, organic substances, N, P
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