Bioenergetic Evaluations of Microbial Metabolisms in Hydrothermal Ecosystems, Taiwan
Date Issued
2009
Date
2009
Author(s)
Chen, Kuan-Chiao
Abstract
Thermophilic microorganisms using chemical compounds to carry on their metabolisms not only are limited by geological and geochemical characteristics but also enhance geological and geochemical cycling in hydrothermal ecosystems. Hot springs are widely hosted in igneous, metamorphic and sedimentary rocks in Taiwan. These diverse natural habitats for thermophilic microorganisms are ideal studying sites to understanding the interaction between microbial communities and geochemical circumstance in various geological regions. On the basis of geochemical compositions, free energy and energy flux could be calculated for certain reactions. Such evaluation would provide a complete and quick way to clarify the energetic metabolic pathways, to understand the competition among microbial populations and to reveal the relationship between community structures and environmental factors in various Taiwan hot springs ecosystems. This study sampled 16 hot springs derived from three geological domains, the northern volcanic region, the eastern metamorphic region and the western sedimentary region. Anions, cations, organic acids, dissolved gases, as well as minerals were measured in these hot springs. Chemical analyses showed that various electron donors, including H2, NH4+, Fe2+, H2S, CH4 and organic acids and electron acceptors, including O2, NO3-, Fe3+, SO42-, S0 and CO2 were available in Taiwan hot spring ecosystems. According to the thermodynamic principle and the concept of lowest free energy requirement, energetic metabolic pathways were revealed by the calculation of free energy and energy flux of various chemical reactions. Energetic metabolic reactions and their energy flux basically depended on the availability and concentration of electron acceptors and donors in different regions. Whether the metabolic reaction can continuously provide energy for the microorganism in the hot spring was also evaluated by the free energy and energy flux change due to certain geochemical variations. Most energetic metabolism pathways should be persistent despite of the dynamic change of chemical and physical conditions. These results were generally supported by molecular biology and microbial incubation analyses. The structure and the competition within microbial community were examined in the view of geochemical conditions and energy flux in the hydrothermal ecosystems.
Subjects
hydrothermal ecosystem
thermophilic microorganism
metabolism
free energy
energy flux
Type
thesis
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