Life Sciences Commons^™

Unraveling Plant-Microbe-Microbe Interactions: Host And Microbial Colonization Determinants Across Experimental Scales, Bridget O'Banion

Doctoral Dissertations

Plant microbiomes are assembled and modified through a complex milieu of biotic and abiotic factors. Despite dynamic and fluctuating contributing variables, specific host and microbial mechanisms are likely important mediators of interactions. We combine information from large-scale datasets across diverse plant hosts with experimental genetic manipulation assays in model Arabidopsis seedlings to converge on a conserved role for metabolite production and transport in mediating host-microbe interactions. Applying a diverse set of analytical tools to microbial communities at various complexity levels will advance our knowledge of the scalability of observed phenotypes and, ultimately, help to decipher the mechanisms dictating plant–microbe interactions …

Characterizing Tmx And Chemotactic Receptor Arrays Through Bacterial Two-Hybrid And Beta-Galactosidase Assays, Adam Keith Hubler

Faculty Publications and Other Works -- Biochemistry, Cellular and Molecular Biology

No abstract provided.

Characterization Of The Chea2 Chemotaxis Operon In Azospirillum Brasilense, Erin Lutz

Chancellor’s Honors Program Projects

No abstract provided.

Effects Of Plant Root Exudates On Bacterial Chemotaxis, Quincy A. Banks

Chancellor’s Honors Program Projects

No abstract provided.

Influence Of Tlp5, Che1p, Tlp4a, And Che4stas Promoters On Chemotaxis In Azospirillum Brasilense, Brian W. Connor

Chancellor’s Honors Program Projects

No abstract provided.

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 …

Localization Of Chemoreceptors In Azospirillum Brasilense., Anastasia Aksenova

Masters Theses

In order to ensure their survival, bacteria must sense and adapt to a variety of environmental signals. Motile bacteria are able to orient their movement in a chemical gradient by chemotaxis. During chemotaxis, environmental signals are detected by chemotaxis receptors and are propagated via a signal transduction cascade to affect bacterial motility. In a model organism Escherichia coli, chemotaxis receptors, also called MCPs (for methyl-accepting chemotaxis proteins) sense changes in concentration gradients by making temporal comparisons about the chemical composition of their surroundings. Decreased attractant concentration or increased repellant concentration results in conformational changes in the MCPs that culminate …

Characterization Of Bacterial Chemotaxis Receptors Sensing And Signaling, Molly Elizabeth Payne

Chancellor’s Honors Program Projects

No abstract provided.

Application Of Computational Molecular Biophysics To Problems In Bacterial Chemotaxis, Davi Ortega

Doctoral Dissertations

The combination of physics, biology, chemistry, and computer science constitutes the promising field of computational molecular biophysics. This field studies the molecular properties of DNA, protein lipids and biomolecules using computational methods. For this dissertation, I approached four problems involving the chemotaxis pathway, the set of proteins that function as the navigation system of bacteria and lower eukaryotes.

In the first chapter, I used a special-purpose machine for molecular dynamics simulations, Anton, to simulate the signaling domain of the chemoreceptor in different signaling states for a total of 6 microseconds. Among other findings, this study provides enough evidence to propose …

Characterization Of Chemosensing In The Alphaproteobacterium Azospirillum Brasilense , Matthew Hamilton Russell

Doctoral Dissertations

Motile bacteria must navigate their environment in constant search of nutrients to sustain life. Thus they have evolved precise and adaptable sensory systems to achieve this goal, making the navigation system of the model bacterium Escherichia coli the best characterized signal transduction pathway in Biology. However, many bacteria have evolved more sophisticated arsenals for sensing and responding to their environment including chemoreceptors to identify novel attractants in the microenvironment. The diazotrophic alphaproteobacterium Azospirillum brasilense inhabits the soil and colonizes the roots of cereals like rice, corn, and wheat. Like most proteobacterial, A. brasilense encodes multiple chemotaxis-like pathways, 4, of which …

Characterization Of The Che4 Signal Transduction Pathway In Taxis Behaviors Of Azospirillum Brasilense, Dhivya Kumar

Masters Theses

Azospirillum brasilense is a gram negative, soil diazotroph that colonizes the roots of agronomically important crops. Studies have shown that swimming motility is an important trait for its survival and colonization of plant roots by these bacteria. Taxis responses, such as chemotaxis and aerotaxis, depend on the ability of the organism to bias its movements in the presence of gradients. The recently sequenced genome of A. brasilense has been shown to possess four chemotaxis operons, but the dominant pathway that modulates swimming behavior by affecting swimming bias in this organism is unknown. Characterization of one of the chemotaxis operons, Che1, …

Characterization Of The Function Of The Azospirillum Brasilense Che1 Chemotaxis Pathway In The Regulation Of Chemotaxis, Cell Length And Clumping, Amber Nicole Bible

Doctoral Dissertations

Azospirillum brasilense is a gram-negative alphaproteobacterium that lives in the soil where it colonizes the root surfaces of cereals and grasses. The genome of A. brasilense has recently been sequenced and shown to possess four different chemotaxis-like operons. This dissertation project focused on characterizing the Che1 chemotaxis-like signal transduction pathway, which was initially implicated in regulation of the chemotaxis behavior. Deletions of individual genes within the Che1 pathway did not exhibit a null chemotaxis phenotype, leading us to investigate the role of this pathway in the lifestyle of A. brasilense and the mechanism(s) by which it functions. We have used …

Identifying Mechanisms Associated With Innate Immunity In Cows Genetically Susceptible To Mastitis, Alexandra Alida Elliott

Doctoral Dissertations

Mastitis, or mammary gland inflammation, causes the greatest loss in profit for dairy producers. Mastitis susceptibility differs among cows due to environmental, physiological, and genetic factors. Prior research identified a genetic marker in a chemokine receptor, CXCR1, associated with mastitis susceptibility and decreased neutrophil migration. Current research seeks to identify reasons behind mastitis susceptibility by validating this model through in vivo challenge with Streptococcus uberis and studying specific mechanisms causing impaired neutrophil migration. Holstein cows with GG (n=19), GC (n=28), and CC (n=20) genotypes at CXCR1+777 were challenged intramammarily with S. uberis strain UT888. After challenge 68% of quarters from …

Characterizing Cell-Cell And Cell-Surface Interactions In The Rhizobacterium Azospirillum Brasilense, Calvin Shay Green

Masters Theses

Microaerophilic and chemotaxic diazotrophs, azospirilla are found in close association with certain cereals such as durum wheat and maize and are active in enriching these ecological niches with the macronutrient nitrogen as ammonia. Regarded as highly pleomorphic, Azospirillum spp. are highly motile, using either a single polar flagellum when grown in liquid environments or peritrichous lateral flagella in viscous environments. Additionally, azospirilla are able to adhere onto surfaces as a biological film or aggregate cell-to-cell as nonproliferating flocculi, and these two processes having been suggested as positively affecting the survival and dispersal of the bacteria in the soil. Even though …

Use Of Proteomics Tools To Investigate Protein Expression In Azospirillum Brasilense, Gurusahai K. Khalsa-Moyers

Doctoral Dissertations

Mass spectrometry based proteomics has emerged as a powerful methodology for investigating protein expression. “Bottom up” techniques in which proteins are first digested, and resulting peptides separated via multi-dimensional chromatography then analyzed via mass spectrometry provide a wide depth of coverage of expressed proteomes. This technique has been successfully and extensively used to survey protein expression (expression proteomics) and also to investigate proteins and their associated interacting partners in order to ascertain function of unknown proteins (functional proteomics). Azospirillum brasilense is a free-living diazotrophic soil bacteria, with world-wide significance as a plant-growth promoting bacteria. Living within the rhizosphere of cereal …