Filtering by
- All Subjects: Microbial Ecology
- Creators: Cadillo-Quiroz, Hinsby
Permafrost degradation is leading to rapid wetland formation in northern peatland ecosystems, altering the role of these ecosystems in the global carbon cycle. I reviewed the literature on the history of the MPP theory, including tracing its origins to The Second Law of Thermodynamics. To empirically test the MPP, I collected soils along a gradient of ecosystem development and: 1) quantified the rate of adenosine triphosphate (ATP) production--literally cellular energy--to test the MPP; 2) quantified greenhouse gas production (CO2, CH4, and N2O) and microbial genes that produce enzymes catalyzing greenhouse gas production, and; 3) sequenced the 16s rRNA gene from soil microbes to investigate microbial community composition across the chronosequence of wetland development. My results suggested that the MPP and other related theoretical constructs have strong potential to further inform our understanding of ecosystem development. Soil system power (ATP) decreased temporarily as the ecosystem reorganized after disturbance to rates of power production that approached pre-disturbance levels. Rates of CH4 and N2O production were higher at the newly formed bog and microbial genes involved with greenhouse gas production were strongly related to the amount of greenhouse gas produced. DNA sequencing results showed that across the chronosequence of development, the two relatively mature ecosystems--the peatland forest ecosystem prior to permafrost degradation and the oldest bog--were more similar to one another than to the intermediate, less mature bog. Collectively, my results suggest that ecosystem age, rather than ecosystem state, was a more important driver for ecosystem structure and function.
Roux-en-Y gastric bypass (RYGB) rearranges the gastrointestinal tract and reduces gastric acid secretions. Therefore, pH could be one of the factors that change microbiome after RYGB. Using mixed-cultures and co-cultures of species enriched after RYGB, I showed that as small as 0.5 units higher gut pH can aid in the survival of acid-sensitive microorganisms after RYGB and alter gut microbiome function towards the production of weight loss-associated metabolites. By comparing microbiome after two different bariatric surgeries, RYGB and laparoscopic adjustable gastric banding (LAGB), I revealed that gut microbiome structure and metabolism after RYGB are remarkably different than LAGB, and LAGB change microbiome minimally. Given the distinct RYGB alterations to the microbiome, I examined the contribution of the microbiome to weight loss. Analyses revealed that Fusobacterium might lessen the success of RYGB by producing putrescine, which may enhance weight-gain and could serve as biomarker for unsuccessful RYGB.
Finally, I showed that RYGB alters the luminal and the mucosal microbiome. Changes in gut microbial metabolic products occur in the short-term and persist over the long-term. Overall, the work in this dissertation provides insight into how the gut microbiome structure and function is altered after bariatric surgery, and how these changes potentially affect the host metabolism. These findings will be helpful in subsequent development of microbiome-based therapeutics to treat obesity.
Tropical peatlands play a critical role in global carbon storage and greenhouse gas flux, yet the role of microbial communities in these ecosystems remains poorly understood. Methane-oxidizing bacteria (MOB) are considered an efficient biological filter for methane and can mitigate its release into the atmosphere, facilitating an ecosystem’s capacity to become a net sink. Prokaryotic gene amplicon surveys targeting a unique biomarker instead of a universal one (i.e., 16S rRNA) can reveal a more comprehensive analysis of microbial communities with ecological functions (i.e., methanotrophy). The alpha subunit of particulate methane monooxygenase (pmoA) is commonly targeted as a phylogenetic biomarker for both aerobic and anaerobic MOB. Here, we tested three different primer sets and investigated their ability to assess methanotrophic diversity across three biogeochemically distinct tropical peatland sites in the Pastaza-Marañón foreland basin (PMFB) in western Amazonia. The results showed that sequencing using 16S rRNA and pmoA genes revealed differences in MOB taxonomic identification in 21 tropical peat soils. Beta diversity analysis of pmoA genes suggests that site location is not the main driver of differences in MOB community makeup. This work offers insight into the strengths and weaknesses of targeted gene amplicon surveys using 16S and pmoA from tropical peat soils as a case study.