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Assessing the role of soil chemoautotrophs in carbon cycling: An investigation into isotopically labelled soil microorganisms

Hart, Kris M (2011) Assessing the role of soil chemoautotrophs in carbon cycling: An investigation into isotopically labelled soil microorganisms. PhD thesis, Dublin City University.

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Abstract

Recently observed increases in atmospheric CO2 have created great interest in carbon capture technologies and natural sinks of this major component of the carbon cycle. Humic substances are a large, operationally defined fraction of soil organic matter. It was thought that humic substances consist of cross-linked macromolecular structures forming a distinct class of compounds. However, it was recently concluded by members of my research group that the vast majority of humic material in soils, are a complex mixture of microbial/plant biopolymers and degradation products, and not a distinct chemical category. The postulation that microbial inputs to soil carbon are greatly underestimated was put forward by my research group in 2007. Therefore, I have attempted to demonstrate the inputs made by soil chemoautotrophic bacteria. A method was developed where soil samples were measured for chemoautotrophic activity by subjecting them to a suite of scientific techniques. A growth chamber was used to propagate extant soil chemoautotrophic bacteria from different soils and subjected to an array of chemical and biological analyses. The growth chamber was used to measure CO2 concentrations and introduce stable isotopic 13CO2. Estimations of CO2 sequestration were made using direct measurements for Irish soils and one Eurasian soil. Isotope labelled DNA was isolated using cesium chloride gradient ultracentrifugation. The dominant chemoautotrophic bacteria uncovered were Thiobacillus denitrificans and Thiobacillus thioparus. Labelled biomass was isolated and described using GCMS-IRMS and NMR, where an array of PLFAs, protein/peptide, carbohydrates and aliphatics were observed. Finally, an attempt to mimic common agricultural practice was performed to measure soil chemoautotrophic activity. This demonstrated the capability of this approach to benefit carbon flux estimations and hopefully in the future help to elucidate carbon flow into soils for the greater environment.

Item Type:Thesis (PhD)
Date of Award:November 2011
Refereed:No
Supervisor(s):Kelleher, Brian
Uncontrolled Keywords:carbon cycle; atmospheric CO2; Humic substances; soil organic matter
Subjects:Physical Sciences > Analytical chemistry
Biological Sciences > Molecular biology
Physical Sciences > Environmental chemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
Funders:Science Foundation Ireland, Environmental Protection Agency
ID Code:16610
Deposited On:30 Nov 2011 14:30 by Brian Kelleher. Last Modified 30 Nov 2011 14:30

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