Date of Award
Doctor of Philosophy (PhD)
The relative importance of different microbial energy metabolisms in varying environments, and so their environmental impacts, are not well understood. This study combined geochemical analysis, bioenergetic calculations, analysis of environmental small subunit ribosomal RNA and functional genes, and culturing studies, to investigate microbial sulfur cycling on the surface of Borup Fiord Pass Glacier, Canadian High Arctic. The particular focus was to investigate how well the relative amounts of energy available from different redox reactions predicted the microbial utilization of those reactions, as indicated by relative abundance of key functional genes. Bioenergetics accurately predicted that the most abundant energy-related genes would be those used in the oxidation of sulfur species. However, genes for oxygenic or anoxygenic photosynthesis, aerobic and anaerobic oxidation of ammonium were largely or completely absent, even though these all represented energy sources that could in principle sustain life in this environment.
This investigation also found that the deposit on which the metagenome analysis was performed was dominated by Sulfurovum sp. and Sulfuricurvum sp. the first time these Epsilonproteobacteria have been seen to be abundant in a sub-aerial environment. The data strongly support the hypothesis that these Epsilonproteobacteria were the dominant primary producers of this community, using sulfur redox reactions, and in particular the oxidation of S0, to obtain energy. The genes responsible for oxidizing S0 are not fully known, but the disproportionately-high relative abundance of DsrE genes raises the possibility that the DsrE gene in these Epsilonproteobacteria might be involved in mobilizing external S0.
The surface layer of the deposit was dominated by Flavobacterium sp. which may therefore have a previously-unrecognized ability to metabolize sulfur compounds. This organism was isolated, and in culture it oxidized thiosulfate to sulfate, but was not able to conserve energy from this reaction. A Borup Gillisia sp. isolate, also a member of the Flavobacteriaceae family, demonstrated the ability to create unusual S0-biomineralized structures in culture, a previously unknown ability for Flavobacteria.
Wright, Katherine Elizabeth, "Bioenergetic and Metagenomic Analysis of Microbial Sulfur Cycling at Borup Fiord Pass Glacier, Canadian High Arctic" (2012). Molecular, Cellular, and Developmental Biology Graduate Theses & Dissertations. 14.