Organizational Unit:
School of Biological Sciences

Permanent Link
https://hdl.handle.net/1853/70750
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
ArchiveSpace Name Record
https://finding-aids.library.gatech.edu/agents/corporate_entities/1131

Filters

2022 3
3
3
3
Reset filters

Settings
End date: 2022 × Start date: 2022 × search.filters.applied.f.isOrgUnitOfPublicationTitle: School of Biological Sciences × search.filters.applied.f.resourcesubtype: Thesis ×

Publication Search Results

Now showing 1 - 3 of 3
Thumbnail Image
Item

Nitrate and Phosphate Loads, but not Light Availability, Impact Freshwater Phytoplankton Diversity via Tradeoffs Between Dominant Species

2022-12-01 , Southard, Michael Kelton

Eutrophication of freshwater ecosystems, mainly caused by nitrogen (N) and phosphorus (P) pollution, causes significant economic damages every year in the U.S. Excess N and P deposition in lakes can result in harmful algal blooms, reduced biodiversity, and increased greenhouse gas production, but we still do not fully understand how and why phytoplankton communities react to nutrient enrichment under varying conditions. Several theories – including the niche dimension hypothesis, biomass-driven competition hypothesis, nitrogen detriment hypothesis, and benthic model – are currently being explored in both terrestrial and aquatic producer communities in attempt to better understand the biological mechanisms effecting these systems, and the goal of this study was to determine which models are most applicable to freshwater phytoplankton. Using five-species microcosms of green algae, we found that N and P enrichment significantly reduced diversity (independent of light availability), which was likely mediated through nutrient tradeoffs between the two dominant species, Ankistrodesmus falcatus and Selenastrum capricornutum. Additionally, we observed a significant decrease in monoculture carrying capacity across all species with high N addition in low P concentrations, indicating that high N:P ratios may be physiologically harmful to green algae. These findings suggest that the niche dimension and nitrogen detriment hypotheses may be the most applicable to freshwater phytoplankton communities and could be useful for protecting and mitigating economic losses from these systems.

View
Thumbnail Image
Item

Characterization of chromatinized hydrogen peroxide biosensor in cancer cells

2022-06-02 , Pfliger, Jessica M.

Hydrogen Peroxide (H2O2) is an important eukaryotic signaling molecule regulating cellular processes. As one of the most abundant reactive oxidative species (ROS), H2O2 can cause oxidative stress and cytotoxicity at elevated concentrations leading to DNA damage and programmed cell death. Despite the recent advancements in modulating ROS responses for potential cancer therapies, little is known about nuclear ROS temporal emergence and dynamics. To investigate the role of nuclear ROS and H2O2 in chromatin, we established a genetically engineered chromatin-targeted biosensor for H2O2, H2B-HyPer, by fusion of HyPer, a specific H2O2 biosensor, with core histone H2B. In this thesis, I utilized fluorescent microscopy and fluorescent recovery after photobleaching (FRAP) to study the H2O2 dynamics within the chromatin of HCT116 colon cancer cells containing genetically integrated H2B-HyPer. I demonstrate that H2B-HyPer is localized in the nucleus of HCT116/H2B-HyPer cells with an average residence time and mobile fraction of 9.14 minutes and 20.59%, respectively, comparable to the core histones in chromatin. I then show that H2B-HyPer is sensitive to changes in H2O2 levels post addition of H2O2 or DTT in culture medium. Further analysis of H2B-HyPer kinetics revealed a rapid increase and recovery of H2B-HyPer signal intensity in HCT116/H2B-HyPer cells upon treatment with and the removal of H2O2. Altogether, these studies establish H2B-HyPer as an effective biosensor for real-time spatio-temporal tracking of chromatin-proximal H2O2 dynamics.

View
Thumbnail Image
Item

Trophic structure in the Western Tropical North Atlantic Ocean using Stable Isotope Abundances (δ15N and δ13C)

2022-05-06 , Salter, Shannon Marie

We investigated the biomass concentration and natural abundance of nitrogen and carbon stable isotopes (δ15N and δ13C) of size-fractionated zooplankton collected on two cruises to the Amazon River Plume (ARP) region. Mean animal biomass concentration was 3.34 mg/m2 during the day and 2.68 mg/m2 on Cruise EN614. The mean biomass on Cruise EN640 was 7.22 mg/m2 during the day and 9.60 mg/m2 at night. . Sampling stations were classified into habitat types based on biologically relevant physical and chemical parameters: the young plume core (YPC), old plume core (OPC), outer plume margin (OPM), western plume margin (WPM), and oceanic seawater (OSW). In general, zooplankton δ15N varied markedly and significantly among habitats for both cruises, with generally higher values in the YPC, OPC, WPM, and OSW habitats relative to the OPM habitat. Zooplankton δ15N values reflect the sources of nitrogen supporting biological production, and trophic processing within the food web. Suspended particles collected from these habitats showed lower δ15N values than the zooplankton, but we did not find a consistent increase in animal δ15N with size. Vertical migration led to diel shifts in zooplankton δ15N at the surface, with generally higher δ15N values at night than during the day during both cruises. Zooplankton δ13C values varied less than their δ15N, with no significant differences among habitats or with animal size.

View