Master of Science, The Ohio State University, 2017, Microbiology

Permafrost, which stores approximately 50% of global soil carbon, is thawing rapidly due to climate change, and resident microbes are contributing to changing greenhouse gas emissions. Predictions of the fate of carbon in these regions is poorly constrained. However, improved, careful mapping of microbial community members influencing carbon dioxide and methane emissions will help clarify the system response to continued change. In order to more fully understand connections between the microbial communities, major geochemical transformations, and carbon dioxide and methane emissions, peat cores were collected from the active layers of three permafrost habitats spanning a thaw gradient (collapsed palsa, bog, and fen) at Stordalen Mire, Abisko, Sweden. Anaerobic incubations of shallow and deep subsamples from these sites were performed, with time-course characterization of the changes in microbial communities, peat geochemistry, and carbon dioxide and methane production. The former were profiled with 16S rRNA amplicon sequencing, and select metagenomes. The communities within each habitat and depth were statistically distinct, and changed significantly over the course of the incubations. Overall, Acidobacteria was consistently the dominant microbial phylum in incubations from all three habitat types. With increased thaw, the relative abundance of Actinobacteria tended to decrease, while Chloroflexi and Bacteroidetes increased with thaw; these phyla trends are consistent with microbial communities in the field. The relative abundance of methanogens increased with thaw, and with depth in collapsed palsa and bog samples; this is consistent with the later, more inundated thaw stages and deeper depths being more anoxic and providing conditions favorable to methanogens. Additionally, the microbial biodiversity in the incubations decreased over incubation time. Next, we focused on a polyphyletic group of microbes known as homoacetogens. Homoacetogenesis (CO2 + H2 -> CH3COOH) (open full item for complete abstract)

Committee: Virginia Rich (Advisor); Mike Wilkins (Committee Member); Kelly Wrighton (Committee Member) Subjects: Microbiology