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Browsing by Subject "microscopy"

Now showing 1 - 4 of 4
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    Mammal Mediated Dispersal of Mycorrhizal Fungi: Using Microscopy as a Method for Quantifying Diet and Fungal Richness
    (2024-04-30) Weiss, Teagan; Joyce, Michael; Stephens, Ryan; Moen, Ron
    Small mammals help initiate mycorrhizal fungal networks by consuming fungi and dispersing spores through their scat. Quantifying small mammal diets can help define the role these species play in mediating the colonization of mycorrhizal fungal networks that play important roles in ecosystem health such as soil aggregation, carbon sequestration, and tree establishment. In this study, fecal material was collected from the gastrointestinal tracts of small mammal specimens to be analyzed for diet quantification. Preliminary results found red-backed voles to have the greatest fungal abundance on average, with fungi making up 83% of their diet. Short-tailed shrew diets were composed primarily of insects, while White-footed mice and Deer-mice diets were composed primarily of plants and insects.
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    Molecular Bases of Interaction Between Soybean Cyst Nematode and Antagonistic Soil Fungi
    (2022-06) Kim, Dong-gyu
    A diverse community of soil fungi antagonize the economically consequential plant-parasitic soybean cyst nematode (SCN; Heterodera glycines) through direct parasitism, secretion of bioactive secondary metabolites, or a combination of both. Characterizing fungal antagonism towards SCN eggs, and conversely the responses of SCN to fungal antagonism, may help better understand the dynamics, mechanisms and targeted molecular processes involved, and ultimately lead to the formulation of more effective fungal biocontrol agents or biopesticides. Chapter 2 describes fluorescence microscopic observations and transcriptomic expression patterns determined from SCN eggs placed in co-culture on top of fungal cultures of Pochonia chlamydosporia 123 and Ilyonectria sp., sampled at multiple timepoints (1, 3 and 5 days) of interaction. The non-specific cellulose and chitin stain Calcofluor White M2R and DNA-intercalating apoptosis stain propidium iodide were used for fluorescent labeling of fungal structures and nematode apoptosis within SCN eggs, respectively. Using this combination of microscopic and transcriptomic approaches, I characterized potential differences in interactions between SCN eggs and the two fungal isolates in the framework of established modes of pathogenicity of fungal pathogens of plants (i.e. biotrophy and necrotrophy), as well as uncover genes potentially involved in the perception and immune responses by SCN against these fungal antagonists. Chapter 3 pursues the chemical basis of antagonism of two Ilyonectria field isolates (Ilyonectria sp. and E413-17) using a bioactivity-guided fractionation approach to procedurally identify samples for purification and characterization. This chapter also examines candidate genes in early timepoints of SCN lifecycle for their suitability as housekeeping genes in qPCR applications for future studies to examine genes of interest.
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    Structure Determination of Zeolite Nanosheets
    (2012-06-13) Zhang, Xueyi; Tsapatsis, Michael
    none
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    Towards the Ultimate Spatiotemporal Resolution in Low-Repetition Rate, Laser-Based Ultrafast Electron Microscopy: Theoretical and Experimental
    (2022-09) Curtis, Wyatt
    Since its inception, ultrafast electron microscopy (UEM) has proved to be a versatile tool for probing sub-nanosecond dynamics in materials. Combining the high resolutions of traditional TEM with ultrafast pump-probe techniques, UEM allows scientists to observe optically induced dynamics in both real and reciprocal space. However, deleterious electron-electron interactions lead to both spatial and energetic broadening, reducing the ability to image subtle dynamics. An approach to overcoming these interactions has been to generate images using single electron packets, which limits packet degradation due to the absence of space-charge. In this regime, a careful balance must be struck between laboratory stability and repetition rate, as long acquisitions must be used to form a coherent image. However, innate instrument parameters and architecture also play a key role in the shaping of the single-electron beam quality. Presented in this work, is a set of systematic simulations of the thermionic electron gun in a minimally modified system. Using particle tracing simulations, we have explored the intricate link between photoemission properties, the internal electrostatic architecture of the TEM and their effects on collection efficiency, temporal resolution, and chromatic aberrations. We have found that careful consideration of electron emission and the diameter of the Wehnelt aperture must be taken in order to assume utmost beam quality. This portion of work ultimately serves as the foundation for a large, multi-faceted effort to map the entire parameter space for minimally modified UEM. In addition to these simulations, the first steps towards low repetition rate, high resolution UEM are performed. Using an un-floated TEM column, we are able to demonstrate near-instrument limited resolution using a thermionic electron beam. In addition, we perform a direct comparison between the imaging capabilities of pulsed and thermionic electron beams. In an effort to push the limits of specimen relaxation, we show that nanometer scale resolution is achievable for long acquisition times (80-120s), dose rates as low as 0.014 e- Å-2 s-1, and probe repetition rates as low as 10 kHz. We also demonstrate at similarly low repetition rates we are able to continuously resolve nanometer scale features over multiple hours, the duration of an ultrafast experiment while under specimen illumination. These results provide the fundamental proof-of-ability for direct observation of real-time, nanometer scale materials dynamics in UEM and lay the groundwork and methodology for the realization of low repetition rate Å-fs spatiotemporal resolution. In tandem with efforts to improve the resolving capabilities of ultrafast pulsed electron beams, this work also provides the design and implementation of a custom in situ laser beam profiler. Upon the final development of this specialty holder, unparalleled access to the specimen excitation profiles will be possible. In total, the work presented here demonstrates a developmental effort to achieve the highest possible resolutions in low repetition rate, laser based UEM using both experimental and theoretical methodology.