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Articles 1 - 8 of 8
Full-Text Articles in Life Sciences
Long-Term Impacts Of Tillage, Cover Crops, And Nitrogen Rates On Microbial Community Dynamics And Soil Quality Parameters Under Continuous Cotton Production In West Tennessee, Lilian Wanjiru Mbuthia
Long-Term Impacts Of Tillage, Cover Crops, And Nitrogen Rates On Microbial Community Dynamics And Soil Quality Parameters Under Continuous Cotton Production In West Tennessee, Lilian Wanjiru Mbuthia
Doctoral Dissertations
Microbial communities play a central role in nutrient cycling and soil quality in agro-ecosystems. This research focused on a comparative analysis of the microbial community structure and activity of soils on long-term (31 years) continuous cotton- Gossypium hirsutum L., production in West Tennessee under conservation agricultural (CA) and conventional tillage practices that included: Nitrogen (N) fertilizer rates (N-rates) (0, 34, 67 and 101 kg N per ha); Cover crops (Hairy vetch-Vicia villosa and winter wheat- Triticum aestivum, and a No Cover control); and Tillage (Till and No-till). It was expected that microbial diversity, activity and soil quality would be …
Comparative Genomics Of Microbial Chemoreceptor Sequence, Structure, And Function, Aaron Daniel Fleetwood
Comparative Genomics Of Microbial Chemoreceptor Sequence, Structure, And Function, Aaron Daniel Fleetwood
Doctoral Dissertations
Microbial chemotaxis receptors (chemoreceptors) are complex proteins that sense the external environment and signal for flagella-mediated motility, serving as the GPS of the cell. In order to sense a myriad of physicochemical signals and adapt to diverse environmental niches, sensory regions of chemoreceptors are frenetically duplicated, mutated, or lost. Conversely, the chemoreceptor signaling region is a highly conserved protein domain. Extreme conservation of this domain is necessary because it determines very specific helical secondary, tertiary, and quaternary structures of the protein while simultaneously choreographing a network of interactions with the adaptor protein CheW and the histidine kinase CheA. This dichotomous …
Diversity And Function Of Sulfur Cycling Microorganisms In Sediments From Subglacial Lake Whillans, Antarctica, Alicia Marie Purcell
Diversity And Function Of Sulfur Cycling Microorganisms In Sediments From Subglacial Lake Whillans, Antarctica, Alicia Marie Purcell
Masters Theses
There is a growing consensus that metabolically and phylogenetically diverse assemblages of microorganisms mediate subglacial nutrient and elemental cycling. Subglacial Lake Whillans (SLW), located under 801 m of glacial ice, was recently penetrated using environmentally clean protocols. SLW is a permanently dark, cold (-0.5 °C [degrees Celsius]), and shallow (~2.2 m) freshwater lake beneath the West Antarctic Ice Sheet. The presence and diversity of key functional genes involved in dissimilatory sulfur oxidation and reduction were examined at various depths in two sediment cores taken from SLW. Our data show a diversity of sulfur transformation genes throughout the top 34 cm …
Systems Biology Of Microcystis Blooms, Morgan Michelle Steffen
Systems Biology Of Microcystis Blooms, Morgan Michelle Steffen
Doctoral Dissertations
Cyanobacterial harmful algal blooms (cHABs) degrade freshwater lakes worldwide. Accumulation of nuisance biomass and production of noxious secondary metabolites can result in an expansive impact on both lake ecology and the surrounding communities. The cHAB forming organism Microcystis aeruginosa is known to produce the toxin microcystin, a compound nicknamed “fast death factor,” which has been implicated in animal poisonings and human liver failure and cancers. M. aeruginosa inhabits a wide range of freshwater lakes around the world, such as Lake Erie (USA/Canada) and Lake Tai (Taihu, China), and is often a dominant member of bloom communities. Such systems are well-studied …
Relationships Among Prochlorococcus Ecotypes Across Oceanic Temperature Ranges, Jeremy Werner Chandler
Relationships Among Prochlorococcus Ecotypes Across Oceanic Temperature Ranges, Jeremy Werner Chandler
Doctoral Dissertations
Prochlorococcus, the world’s smallest known photosynthetic organism, is an open ocean cyanobacterium, thought to be globally significant in nutrient cycling. Genetically and physiologically distinct “ecotypes” of Prochlorococcus populate the world’s subtropical and tropical oceans. A few of these key ecotypes comprise the majority of these populations, with the dominant ecotypes frequently varying as a function of depth and latitude. The mechanisms underlying the specific distributions of the ecotypes remain poorly understood, but temperature was believed to play a key role in latitudinal partitioning. Quantitative PCR (Q-PCR) was used to assess ecotypic abundances across transects spanning the Pacific Ocean from 27°N …
Development Of An Experimental And Computational Platform For Enhanced Characterization Of Modified Peptides And Proteins In Environmental Proteomics, Ritin Sharma
Doctoral Dissertations
Over the last decade, mass spectrometry based proteomics has been established as the front-runner in systems-level protein expression studies. However, with the field progressing into research of more and more complex samples, novel challenges have been raised with respect to efficient protein extraction and computational matching. In this dissertation, various aspects in the proteomics workflow, including experimental and computational approaches, have been developed, optimized and systematically evaluated. In this work, some of the critical factors with respect to proteomics sample preparation, like available biomass, detergent removal methods, and intact protein fractionation to achieve deeper proteome measurements were evaluated. The presented …
Quantitative Characterization Of Proteins And Post-Translational Modifications In Complex Proteomes Using High-Resolution Mass Spectrometry-Based Proteomics, Zhou Li
Doctoral Dissertations
Mass spectrometry-based proteomics is focused on identifying the entire suite of proteins and their post-translational modifications (PTMs) in a cell, organism, or community. In particular, quantitative proteomics measures abundance changes of thousands of proteins among multiple samples and provides network-level insight into how biological systems respond to environmental perturbations. Various quantitative proteomics methods have been developed, including label-free, metabolic labeling, and isobaric chemical labeling. This dissertation starts with systematic comparison of these three methods, and shows that isobaric chemical labeling provides accurate, precise, and reproducible quantification for thousands of proteins. Based on these results, we applied this approach to characterizing …
Urea As A Nitrogen Source For Microcystis Aeruginosa, Bernard Shafer Belisle
Urea As A Nitrogen Source For Microcystis Aeruginosa, Bernard Shafer Belisle
Masters Theses
Over the last decade, Lake Erie has experienced annual harmful algal blooms events dominated by the toxic cyanobacterium Microcystis aeruginosa. It is still unclear what causes Microcystis blooms to occur, but there is broad agreement that eutrophication of freshwater systems from anthropogenic sources (urban, industrial, etc.), has led to their proliferation. In particular, the organic compound urea has been implicated as an important source of anthropogenic nitrogen, due to its increased use in agricultural practices. Currently, urea constitutes more than 50% of the nitrogen used for agricultural fertilizer globally, and its usage has increased more than a 100-fold over …