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- Creators: Barrett, The Honors College
Description
Peatlands are a type of wetlands where the rate of accumulation of organic matter exceed the rate of decomposition and have accumulated more than 30 cm of peat (Joosten and Clark, 2002). Peatlands store approximately 30% of all terrestrial carbon as recalcitrant peat, partially decomposed plant and microbial biomass, while simultaneously producing almost 40% of the globally emitted methane (Schmidt et al., 2016), making peatlands an important component of the carbon budgets. Published research indicates that the efficiency of carbon usage among microbial communities can determine the soil-carbon response to rising temperatures (Allison et al. 2010). By determining carbon consumption in peatland soils, total community respiration response, and community structure change with additions, models of carbon use efficiency in permafrost peatlands will be well-informed and have a better understanding of how the peatlands will respond to, and utilize, increased availability of carbon compounds due to the melting permafrost. To do this, we will sequence Lutose deep core samples to observe baseline microbial community structure at different depths and different age-gradients, construct substrate incubations of glucose and propionate and observe community respiration response via a gas chromatography flame ionization detector, track the glucose and propionate additions with high-performance liquid chromatography (HPLC), and sequence the samples once more to determine if there was a deviation from the initial community structure obtained prior to the incubations. We found that our initial sequencing data was supported by previous work (Lin et al., 2014), however we were unable to sequence samples post-incubation due to time constraints. In this sequencing analysis we found that the strongest variable that made samples biologically similar was the age-gradient site in which they were extracted. We found that the group with glucose additions produced the most carbon dioxide compared with the other treatments, but was not the treatment that dominated the production of methane. Finally, in the HPLC samples that were analyzed, we found that glucose is likely forming the most by-product accumulation from mass balance calculations, while propionate is likely forming the least. Future experimentation should focus on the shortcomings of this experiment. Further analysis of 16S rRNA sequencing data from after the incubations should be analyzed to determine the change in microbial community structure throughout the experiment. Furthermore, HPLC analysis for the several samples need to be done and followed up with mass balance to determine where the added glucose and propionate are being allocated within the soil. Once these pieces of the puzzle are put into place, our original question of how the microbial community structure changes at different depths and age-gradients within permafrost peatlands will be conclusively answered.
ContributorsFrese, Alexander Nicholas (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / van Paassen, Leon (Committee member) / Sarno, Analissa (Committee member) / School of Life Sciences (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Methanogens are methane-producing archaea that play a major role in the global carbon cycle. However, despite their importance, the community dynamics of these organisms have not been thoroughly characterized or modeled. In the majority of methanogenesis models, the communities are approximated as a chemical reaction or divided into two populations based on the most common methanogenic pathways. These models provide reasonable estimate of methanogenesis rates but cannot predict community structure. In this work, a trait-based model for methanogenic communities in peatlands is developed. The model divides methanogens commonly found in wetlands into ten guilds, with divisions based on factors such as substrate affinity, pH tolerance, and phylogeny. The model uses steady-state, mixotrophic Monod kinetics to model growth and assumes peatlands operate as a semi-batch system. An extensive literature review was performed to parameterize the model. The acetoclastic module of the model was validated against experimental data. It was found that this portion of the model was able to reproduce the major result of an experiment that examined competition between Methanosaeta and Methanosarcina species under irregular feeding conditions. The model was analyzed as a whole using Monte Carlo simulation methods. It was found that equilibrium membership is negatively correlated with a guild's half-substrate constant, but independent of the guild's yield. These results match what is seen in simple pairwise competition models. In contrast, it was found that both the half-substrate constant and yield affected a guild's numerical dominance. Lower half-substrate constants and higher yields led to a guild accounting for a greater fraction of community biomass. This is not seen in simple pairwise competitions models where only yield affects final biomass. As a whole, the development of this model framework and the accompanying analyses have laid the groundwork for a new class of more detailed methanogen community models that go beyond the two compartment acetoclastic-hydrogenotrophic assumption. .
ContributorsLopez Jr, Jaime Gerardo (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / Marcus, Andrew (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
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.
ContributorsBrzezinski, Hannah (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / Wojciechowski, Martin (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2022-05