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Microbial contributions to carbon, nitrogen, and greenhouse gas cycling in freshwater terrestrial-aquatic interfaces

Smith, Garrett J
http://orcid.org/0000-0002-1014-5102
http://rave.ohiolink.edu/etdc/view?acc_num=osu1575380962535345

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Microbiology.
Freshwater Terrestrial-Aquatic Interfaces (TAIs) are important for regulating atmospheric Greenhouse Gas (GHG) concentrations due to their immense contributions to nutrient transport and processing on global scales. The diversity and heterogeneity of freshwater TAIs have impaired the development of accurate and precise local, regional, and global biogeochemical models necessary for predicting GHG budgets and impacts under climate change scenarios. One critical knowledge gap hindering model constraints is a minimal understanding of the distribution, ecology, and physiology of the microorganisms controlling gas fluxes between the TAIs and the atmosphere. Describing and quantifying the presence and activities of microorganisms in their natural settings has historically been challenging. The research here utilizes contemporary meta-`omics tools (i.e. metagenomics, metatranscriptomics, metaproteomics, and metabolomics) in order to advance our understanding of the microbial carbon and nitrogen processes in situ that control the GHG cycles in two distinct freshwater TAIs. Freshwater wetlands are the largest natural contributor to atmospheric methane. Methanotrophs, microorganisms that oxidize methane for energy and carbon, are natural filters against increasing methane emissions, but their phylogenetic and metabolic diversity make traditional marker gene-centric and cultivation-dependent approaches unable to accurately account for their activity in natural environments. In Chapter 2, metagenomics and metatranscriptomics were used to examine methanotrophic activity in a freshwater wetland displaying an unusual phenomenon known as the “methane paradox”, in which methane is produced in the oxic horizon rather than only in the deeper anoxic zones. In these soils, methanotrophic activity was dominated by a single lineage of metabolically versatile methanotrophs that responded significantly to seasonal changes. Chapter 4 summarizes the progress made in understanding methane oxidation in natural ecosystems using meta-`omics, and assessed the taxonomic and geographic distribution of methanotrophs in publicly accessible datasets, including numerous freshwater TAIs, across the globe. Chapter 3 focuses on the carbon and nitrogen cycles in high order (larger) river system, which are relatively understudied and previously thought of as simply transport conduits of nutrients to the ocean. In this Chapter, genome-resolved metaproteomics demonstrated that carbon processing was active in the river sediments, but was unexpectedly low compared to nitrogen cycling. Both organic and in inorganic nitrogen were exchanged by previously undescribed taxa in an extensive metabolic network. Surprisingly, activity for the expected step for nitrous oxide production was absent, pointing to significant contributions of alternate pathways, or possibly its consumption in these sediments. In summary, the research presented here advances our knowledge of the microbial contributions to GHG processing in freshwater TAIs by using robust meta-omics frameworks that can increase the accuracy of the parameters for these processes in GHG models.
Kelly Wrighton, PhD (Committee Chair)
Virginia Rich, PhD (Committee Member)
Gil Bohrer, PhD (Committee Member)
Matthew Sullivan, PhDD (Committee Member)
278 p.
Environmental Science; Microbiology; Molecular Biology; Soil Sciences

Recommended Citations

Citations

  • Smith, G. J. (2020). Microbial contributions to carbon, nitrogen, and greenhouse gas cycling in freshwater terrestrial-aquatic interfaces [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1575380962535345

    APA Style (7th edition)

  • Smith, Garrett. Microbial contributions to carbon, nitrogen, and greenhouse gas cycling in freshwater terrestrial-aquatic interfaces. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1575380962535345.

    MLA Style (8th edition)

  • Smith, Garrett. "Microbial contributions to carbon, nitrogen, and greenhouse gas cycling in freshwater terrestrial-aquatic interfaces." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1575380962535345

    Chicago Manual of Style (17th edition)

osu1575380962535345
206
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This open access ETD is published by The Ohio State University and OhioLINK.