Doctoral Dissertations
Date of Award
12-2021
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Microbiology
Major Professor
Karen G. Lloyd
Committee Members
Tatiana A. Vishnivetskaya, Jill A. Mikucki, Sarah L. Lebeis, Andrew D. Steen
Abstract
Permafrost is soil that has remained frozen for at least two years. The active layer is a surface portion above the permafrost that experiences seasonal thaw and refreezing. The environmental characteristics of permafrost and active layer are different but are directly related to each other. As the climate continues to warm, the active layer will expand into the permafrost and the continuously frozen soil will be subjected to seasonal thawing. The organisms that inhabit both the active layer and the permafrost soil will respond differently to the climate based on where in the soil they are present and the soil characteristics. Moreover, the climate will either be inundated with a large amount of microbially mediated greenhouse gasses from increased metabolic activity or it will become a carbon sink with the increased viability for vegetation. Either way, the microbial communities that are present in both the deep permafrost and the active layer will experience changes as the climate continues to warm. Those deep permafrost microbes are either adapted to their current location and can survive in the cold, nutrient-depleted soils, or they are in a hibernation like state; waiting for the warm climate until they can become metabolically active again. Opposingly, the microbes in the active layer could either be the main source of greenhouse gas emissions or they act as a carbon sink and use gasses in microbial metabolism. Either way, studying the microbial interactions in both deep permafrost and active layer are important when assessing how microbial interactions will play a role, and respond, in the changing climate. This dissertation combines metagenomic data in the form of metagenome assembled genomes to assess how microbes at a sample location can interact with its environment. Genetic features in metagenome assembled genomes or from a metagenomic library are used to determine if the organisms that are sequenced are interacting with the geochemical characteristics of their habitat. In the chapters to follow, MAGs are analyzed from Siberian permafrost and Svalbard active layer. Annotated genes from Siberian MAGs show a suite of genes that demonstrate the ancient soils contain genetically adapted microbes. In Svalbard active layer, geochemical analyses are combined with culture independent methods to assess how the microbial community is active in their environment and how microbes will be able to metabolically respond to thaw. Lastly, analysis of MAGs from five Svalbard active layer cores shows how the phyla; Acidobacteriota and Actinobacteriota dominate different locations of the active layer stratigraphy, with the former having high abundance in the upper half of the frozen active layer and the latter dominating in the thawed active layer. These studies show how the microbial interactions with each other, and the environment will affect and be affected when the active layer has a long thawing season.
Recommended Citation
Sipes, Katie, "High Arctic Permafrost Microbial Characterizations: Siberian and Svalbard microbiology of ancient and active layer permafrost. " PhD diss., University of Tennessee, 2021.
https://trace.tennessee.edu/utk_graddiss/6959