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Bacterial role in silicate mineral alteration in near-neutral pH conditions
Duchoslav, Vojtěch ; Falteisek, Lukáš (advisor) ; Seydlová, Gabriela (referee)
It is well established that bacteria are able to catalyze dissolution of silicate minerals. Bacteria may dissolve silicates for two different purposes. They may use certain elements that can undergo redox transitions as substrates for their energetic metabolism or they can leach nutrients, that are otherwise unaccessible in their habitat. The main mechanisms of bacterially mediated silicate leaching are acidic or basic catalysis and surface complexation. The main nutrients extracted are K, Mg, P and Fe. The only element significantly exploited as substrate for dissimilative energetic metabolism is iron. In order to leach iron as a nutrient, even extremely strong complexants (i.e. siderophores) may be employed. However, only moderate complexing agents can serve to obtain iron as terminal electron acceptor. The second possibility is to reduce iron directly in the crystal grid by means of the conductive nanofibres. The oxidative dissolution of silicates by chemoautotrophs is rare, in contrast to that of sulfides. Bacterial dissolution of silicates leaves morphological and geochemical signatures, but it is still problematic to recognize and interpret them. Although it is well-known that bacteria can dissolve most of the rock-forming minerals in diverse environments we are unable to quantify their contribution...
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Microorganisms as the primary producers in photosynthesis-independent ecosystems
Burkartová, Kateřina ; Falteisek, Lukáš (advisor) ; Lhotský, Josef (referee)
Chemolithotrophy and photoautotrophy are the two basic principles of primary production on Earth. This thesis focuses on the relation between chemolithotrophic and oxygen-productive photosynthetic microorganisms in a global dimension. There are high atmospheric oxygen concentration, high sulfate in seawater and other oxidants because of oxygen-productive photosynthesis. These compounds are commonly consumed by chemolithotrophs to oxidize reduced inorganic compounds. It is a question, if there are chemoautotrophic ecosystems profiting only from abiotically derived substrates. It is essential to combine geochemical and metagenomic approaches in order to enhance both establishing of the origin of substrates and assessing the metabolism which utilizes them in the tested ecosystem respectively. Two well established types of photosynthetic independent ecosystems that use serpentinization hydrothermal venting and radiolysis of water as a source of energy are known at present time. The absence of photosynthesis-derived final electron acceptors for chemolithotrophy and the proper spatial separation from areas where photosynthetically derived organic matter and oxidants are present can be a useful clue for this investigation. The goal of this thesis is to describe geological processes which provide not only...
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Bacterial role in silicate mineral alteration in near-neutral pH conditions
Duchoslav, Vojtěch ; Falteisek, Lukáš (advisor) ; Seydlová, Gabriela (referee)
It is well established that bacteria are able to catalyze dissolution of silicate minerals. Bacteria may dissolve silicates for two different purposes. They may use certain elements that can undergo redox transitions as substrates for their energetic metabolism or they can leach nutrients, that are otherwise unaccessible in their habitat. The main mechanisms of bacterially mediated silicate leaching are acidic or basic catalysis and surface complexation. The main nutrients extracted are K, Mg, P and Fe. The only element significantly exploited as substrate for dissimilative energetic metabolism is iron. In order to leach iron as a nutrient, even extremely strong complexants (i.e. siderophores) may be employed. However, only moderate complexing agents can serve to obtain iron as terminal electron acceptor. The second possibility is to reduce iron directly in the crystal grid by means of the conductive nanofibres. The oxidative dissolution of silicates by chemoautotrophs is rare, in contrast to that of sulfides. Bacterial dissolution of silicates leaves morphological and geochemical signatures, but it is still problematic to recognize and interpret them. Although it is well-known that bacteria can dissolve most of the rock-forming minerals in diverse environments we are unable to quantify their contribution...
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