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Articles 1 - 13 of 13
Full-Text Articles in Life Sciences
Response Of Soil Viral And Microbial Functional Diversity To Long-Term Agricultural Management In Jackson, West Tennessee, Ning Duan
Doctoral Dissertations
Soil microbial communities are a critical component for ecosystem stability and function. Viruses, as an important biotic controller, have the potential to regulate the abundance and diversity of bacterial communities through infection. Soil is known to harbor abundant and diverse viral assemblages but their ecological role and influence on microbial processes has not been fully elucidated. Microbes can be influenced by viruses not only from infection but though biogeochemical feedbacks of the “microbial (bacterium–phage–DOC) loop” or “viral shunt”. However, we know relatively little about the microbial community and function under the regulation of viruses in soil and how they respond …
Microbial Community Dynamics Of A Microcystis Bloom, Helena Pound
Microbial Community Dynamics Of A Microcystis Bloom, Helena Pound
Doctoral Dissertations
Harmful algal bloom events are notoriously associated with massive economic and environmental consequences, causing wildlife and human health risks. As these blooms increase in occurrence, duration, and severity around the world, it is essential to understand conditions leading to bloom formation and why they persist. Abiotic factors such as nutrients are commonly considered in bloom dynamics, but biotic interactions with co-occurring microbial species and viruses must also be taken into account. Harmful algal blooms dominated by the cyanobacterial genus Microcystis occur in bodies of water around the world and provide an ideal system in which to study top-down controls on …
Determining The Ecological And Physiological Factors Contributing To The Competitive Success Of Prochlorococcus In The Oligotrophic Ocean, Benjamin C. Calfee
Determining The Ecological And Physiological Factors Contributing To The Competitive Success Of Prochlorococcus In The Oligotrophic Ocean, Benjamin C. Calfee
Doctoral Dissertations
Prochlorococcus is a genus of extremely successful marine cyanobacteria. This success is realized through its pervasive biogeographical range and presence in almost all open ocean environments where it usually it the dominant phytoplankton. Limited capabilities of culturing and genetic manipulation of this organism have resulted in assumptions about this success overwhelmingly based on field observations. These studies have assumed adaptations for resource uptake and utilization in nutrient limited environments to cause dominance of Prochlorococcus over other photosynthetic microbes. In an attempt to definitively explain this through laboratory culture, we developed a culturing system to assay questions of nutrient limitation effects …
Perturbing Fatty Acid Metabolism In Enterococcus Faecalis Disrupts Responses To Exogenous Fatty Acids And The Antibiotic Daptomycin, Rachel D. Johnston
Perturbing Fatty Acid Metabolism In Enterococcus Faecalis Disrupts Responses To Exogenous Fatty Acids And The Antibiotic Daptomycin, Rachel D. Johnston
Doctoral Dissertations
Enterococcus faecalis is an opportunistic pathogen. In the host, it is exposed to fatty acids which impact cellular physiology and induce tolerance to the antibiotic daptomycin. To determine the requirements for induction of daptomycin tolerance, I examined the impacts of blocking de novo fatty acid synthesis or protein synthesis and removing cell wall. I observed that removal of the cell wall induced daptomycin tolerance, indicating that peptidoglycan is necessary for daptomycin to function. As specific exogenous fatty acids induce protection against daptomycin in E. faecalis, I also opted to examine whether incorporation of these free fatty acids was necessary …
High Arctic Permafrost Microbial Characterizations: Siberian And Svalbard Microbiology Of Ancient And Active Layer Permafrost, Katie Sipes
Doctoral Dissertations
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 …
Regulation, Mechanism Of Action, And Function Of A Small Toxin Protein In Ehec, Bikash Bogati
Regulation, Mechanism Of Action, And Function Of A Small Toxin Protein In Ehec, Bikash Bogati
Doctoral Dissertations
The zor-orz locus identified in the chromosome of Escherichia coli O157:H7 EDL933 is a type I toxin-antitoxin system that consists of two homologous gene pairs zorO-orzO and zorP-orzP. The zor genes encode for small toxin proteins and the orz genes encode for small RNAs. Previously it was shown that overproduction of ZorO results in cell growth stasis whereas co-expression of orzO rescues cellular growth. Within, I demonstrate that in addition to growth inhibition, ZorO overproduction results in membrane depolarization and ATP depletion but does not impact the gross morphology of E. coli. In vivo translation and subsequent impacts …
The Effect Of Disturbance And Invasion On Fungal And Plant Communities Over An Elevational Gradient, Adam N. Trautwig
The Effect Of Disturbance And Invasion On Fungal And Plant Communities Over An Elevational Gradient, Adam N. Trautwig
Doctoral Dissertations
High-elevation ecosystems are at risk of disruption from the future effects of climate change. Sub-alpine meadows are a source of unique plant populations, intraspecific variation of elevationally extreme populations, and vital sources of fresh water resources. We evaluated the whole fungal communities, arbuscular mycorrhizal fungal (AMF) communities, plant communities, and edaphic variables of sub-alpine meadows in undisturbed, disturbed, and disturbed with a non-native member of the Brassicaceae (Thlaspi arvense) plots. In conjunction with measuring the effects of disturbance on native communities we conducted potting experiments on a dominant grass of sub-alpine meadows (Festuca thurberi). We also …
Extracellular Polymeric Substances In Oxygenic Photogranules: Investigation Of Their Role In Photogranulation In A Hydrostatic Environment, Wenye Camilla Kuo-Dahab
Extracellular Polymeric Substances In Oxygenic Photogranules: Investigation Of Their Role In Photogranulation In A Hydrostatic Environment, Wenye Camilla Kuo-Dahab
Doctoral Dissertations
The purpose of this dissertation was to assess the critical role of extracellular polymeric substances (EPS) in the photogranulation of activated sludge, in a hydrostatic environment. The first section evaluates the fate and dynamics of different fractions of EPS in sludge-based photogranulation under hydrostatic conditions. The study shows that during the transformation of activated sludge into a photogranular biomass, sludge’s base-extractable proteins selectively degrade. Strong correlations between base-extracted proteins and the growth of chlorophyll a and chlorophyll a/b ratio suggest that the bioavailability of this organic nitrogen is linked with selection and enrichment of filamentous cyanobacteria under hydrostatic conditions. The …
Insights Into Steinernema Carpocapsae-Xenorhabdus Nematophila Specificity And The Role Of Adult Nematode Colonization, Erin Mans
Doctoral Dissertations
The gut microbiota can provide the host with several benefits such as the production of secondary metabolites, essential amino acids, as well as the breakdown of food or protection from pathogens. The host in turn provides the microbiota with shelter and nutrients. Given the benefits that the host and microbiota receive from their association, humans and the microbiota have evolved mechanisms of selection and specificity to assure the proper symbionts colonize a host with high fidelity. Chapter two will explore mechanisms by which Xenorhabdus nematophila nematode intestinal localization (nil) genes interact with and adhere to the nematode intestinal …
Impacts Of Soil Management On Microbial Assemblages Involved In Nitrogen Transformations In Agroecosystems In Tennessee, Usa, Jialin Hu
Doctoral Dissertations
Nutrient reduction, particularly with respect to nitrogen (N) losses, is an important goal for sustainably managed agroecosystems. Soil N-cycling microbial populations that modulate these processes are affected by agricultural management regimes. This research focused on the controls and dynamics of the major N-cycling microbial populations in high-input cotton field under agricultural management regimes and low-input native C4 forage grass systems under pasture management practices to determine the effects of management regimes on in situ seasonal dynamics of the functional microbes responsible for N fixation, nitrification, and denitrification processes. Molecular microbial ecology methods were combined with soil physicochemical properties and …
Applications Of Comparative Genomics And Data Science To Agricultural And Clinical Research, Katrina A. Schlum
Applications Of Comparative Genomics And Data Science To Agricultural And Clinical Research, Katrina A. Schlum
Doctoral Dissertations
The advent of inexpensive, high-throughput whole genome sequencing (WGS) technologies has led to the generation of thousands of related genomes, even from a single study. Large-scale genome analysis has resulted in hypothesis-generating approaches in the fields of clinical, human and agriculture genomics. Additionally, population-level genomic sampling has resulted in a decrease in false positives in genotype-phenotype associations and an increase in understanding of the basis of disease, antibiotic and pesticide resistance. Deeper understanding of migration, genetic divergence and evolution has also been made possible due to WGS. This research applies comparative genomics, population genomics and data science approaches to whole …
Biotic And Abiotic Dehalogenation Of Halogenated Methanes: Trichlorofluoromethane, Dichlorodifluoromethane, And Tetrachloromethane, Briana M. Mcdowell
Biotic And Abiotic Dehalogenation Of Halogenated Methanes: Trichlorofluoromethane, Dichlorodifluoromethane, And Tetrachloromethane, Briana M. Mcdowell
Doctoral Dissertations
Trichlorofluoromethane (CFC-11), dichlorofluoromethane (CFC-12), and tetrachloromethane (CT) are fully halogenated methanes that were produced as refrigerants in the early part of the 1900s and later used in many industrial processes. They are ozone-depleting agents and common groundwater contaminants. They are volatile chemicals that are moderately soluble in water. Due to their volatility when released to the environment, they are predominantly found in the atmosphere, though they also dissolve into the groundwater. In anaerobic environments, they can undergo dehalogenation reactions with several redox-active compounds. This dissertation presents results from two treatability studies from sites contaminated with CFC-11, CFC-12, and CT. Additionally, …
Physiological Constraints, Mechanisms, And Mineral Transformations Of Iron Reduction In Hyperthermophilic Crenarchaea, Srishti Kashyap
Physiological Constraints, Mechanisms, And Mineral Transformations Of Iron Reduction In Hyperthermophilic Crenarchaea, Srishti Kashyap
Doctoral Dissertations
Dissimilatory iron reduction by hyperthermophilic archaea occurs in many geothermal environments and typically relies on microbe-mineral interactions that transform various iron oxide minerals. However, the kinds of iron oxides that can be used, growth rates, extent of iron reduction, and the mineral transformations that occur due to this metabolism are poorly understood. This dissertation improves our fundamental understanding of the physiological mechanisms and mineral transformations of hyperthermophilic iron reduction using two model crenarchaea, Pyrodictium delaneyi and Pyrobaculum islandicum. Using growth yields and metabolite production rates, we demonstrated that a broad range of Fe(III) (oxyhydr)oxides of variable thermodynamic stability was …