Environmental Microbiology and Microbial Ecology Commons^™

Exploring Competitive Dynamics Between Pseudomonas Baetica And Salmonella In A Polymicrobial System, Braxton E.M. Stout

Electronic Theses and Dissertations

The global rise in antimicrobial resistance has catalyzed a greater focus on polymicrobial research aimed at characterizing microbial interactions and uncovering new therapeutic strategies. Though it has long been of interest, environmental soil-derived bacteria remain largely under-represented in research and thus uncharacterized in this field. This project aimed to identify soil microbes that display inhibitory mechanisms to potential nosocomial pathogens. Soil sample S1S3-2 displayed inhibitory phenotypes toward numerous bacteria and was identified as Pseudomonas baetica. In both planktonic and biofilm growth, P. baetica was able to inhibit Salmonella arizonae through a contact-dependent and temperature-dependent manner. Screening of a transposon insertion …

Antimicrobial Responses Of Staphylococcus Aureus In Simulated Spaceflight Conditions, Mikayla Dutkiewicz, Yegor Bushnev

Discovery Day - Daytona Beach

Microbial persistence in confined environments, such as spacecraft, can pose challenges to astronaut health and habitat maintenance. This project investigates Staphylococcus aureus, a Gram-positive bacterium commonly associated with human microbiota and opportunistic infections, in spaceflight-relevant environmental conditions. Further, this project will assess the influence of the antimicrobial/antioxidant compound quercetin to assess its effects on bacterial growth and virulence under standard Earth gravity and simulated International Space Station (ISS) conditions. This approach will assess whether spaceflight-relevant stressors, including microgravity and radiation, alter treatment efficacy by influencing microbial physiology and antimicrobial susceptibility. Data collection and analysis are ongoing, and results are expected …

Investigation Of Biofilm Formation And Osmotic Stress Tolerance Of Nonmotile Escherichia Coli In Simulated Microgravity, Tyler Jenkins

Discovery Day - Daytona Beach

Simulated microgravity presents multiple physiological stressors for astronauts, including bone demineralization, muscle loss, and weakening of the immune system. Bacteria serve as viable model organisms to study physiological changes because of their abundance in the human digestive system and skin. Motility in bacteria plays a significant role in cell survival, but few studies have been conducted on microgravity’s effect on motility phenotypes. While motile strains like Escherichia coli K12 have been studied extensively under microgravity conditions, the effects of simulated microgravity on non-motile strains are largely unknown. To better understand this relationship, the nonmotile E. coli MG1655 strain was inoculated …

From Dust To Growth: Microbial Pathways To Extraterrestrial Farming, Stefani Capasso Villanueva, Nupur Kulkarni

Discovery Day - Daytona Beach

From Dust to Growth: Microbial Pathways to Extraterrestrial Farming addresses the fundamental challenge of sustaining long-term human habitation on other planets. In the era of the Artemis missions, establishing a cost-effective, bioregenerative food source is critical to reducing logistical dependency on Earth, and mitigating the physiological stressors faced by spacecrew through improved nutrition. This study initially investigated the viability of cultivating Mizuna, a proven ISS model organism, in a substrate of Martian regolith simulant amended with organic compost. Following iterative trials, it was found that the plant survival rate was extremely low, even after varying percentages of compost and simulant. …

Effects Of Microgravity And Gamma Radiation On Biofilm Growth, Anya Pavlidis, Kaitlyn Mills Mills, Eva Mcclory, Grant Erlinder, Allen Qiu

Discovery Day - Daytona Beach

Biofilms are collections of bacteria that commonly grow on a variety of surfaces. They are resistant to environmental impacts as bacteria fortify themselves to a surface. Biofilms are commonly found on Earth, but more problematically are also found on spacecraft. On the ISS biofilms have developed in spaces like the workout area, food spaces, and most concerning in the Water Recovery System (WRS). Biofilms tend to react differently to attempted cleaning methods in space than they do on Earth and can be located in extremely difficult to reach places.   This study aims to explore the effects of gamma radiation on …

Function And Regulation Of Long Polar Fimbriae During Enterohemorrhagic Escherichia Coli Infection, Walter J. Galdamez

Dissertations and Theses (Open Access)

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that causes severe gastrointestinal disease and hemolytic uremic syndrome. EHEC employs multiple virulence factors to colonize the host intestine, including the locus of enterocyte effacement (LEE) encoded type III secretion system, intimin, and flagella, yet the role of long polar fimbriae (Lpf) in adhesions and infection remains less well understood. Long polar fimbriae can mediate bacterial attachment to host cells in vitro, yet the regulation and function of its two fimbrial operons, lpf1 and lpf2 in vivo remain poorly understood. Preliminary RNA-seq data from zebrafish infected with EHEC reveal that expression of …

Discovery Of Bmi-Associated Gut Microbiome Signatures In The Awi-Gen 2 Cohort, Meriem Yagoubi

Theses and Dissertations

Obesity is increasing across sub-Saharan Africa amid rapid dietary, environmental, and urbanization transitions, yet the gut microbiome features associated with adiposity in African populations remain under-characterized. This study investigated whether species-level gut microbiome composition is associated with body mass index (BMI) in the AWI-Gen 2 cohort, and whether BMI-associated microbial signals remain detectable after accounting for the dominant geographic structure of the microbiome. Gut microbiome community structure and diversity were characterized across 1,665 participants, and differential abundance analysis was used to identify taxa associated with BMI after controlling for study site. Machine learning models were then trained to assess how …

Microbial Literacy, Equity, And Sustainability At Cal Poly: A Policy Framework With University Housing As A Pilot Case, Joseph B. Fewel

Biological Sciences

Microorganisms play a fundamental role in human health, environmental systems, and the functioning of built environments, yet they remain largely absent from sustainability and public policy discussions. This project proposes a framework for integrating microbial literacy, equity, and health into institutional decision-making, using California Polytechnic State University (Cal Poly) as a case study and university housing as a pilot site for implementation. Drawing on interdisciplinary literature in microbiology, public health, environmental justice, and sustainability, as well as policy analysis and stakeholder interviews, this project examines how campus systems, including housing, ventilation, sanitation, food systems, and waste management, shape microbial exposure …

Exploring The Durability Of Marine Picocyanobacterial Microcolonies, Erik Swanson

University Honors Theses

Picocyanobacteria of the genus Synechococcus are widespread aquatic photoautotrophs that play essential roles in primary production and carbon cycling. Some Synechococcus strains form multicellular microcolonies, but the mechanisms of cell-to-cell attachments and structural durability of these microcolonies remain poorly understood. This research investigated the physical durability of microcolonies in two marine Synechococcus strains (CC9605 and CC9311) using physical disruption treatments. Cultures were subjected to vortexing and sonication treatments, and populations of single cells and microcolonies were quantified using flow cytometry based on differences in measures of size. Results indicated that strain CC9605 showed no significant treatment effect, whereas CC9311 displayed …

Evaluating Soil Health And Crop Yield In Louisiana Agricultural Systems: Impacts Of Best Management Practices And Prediction Models, Hector J. Mendoza Lagos

LSU Doctoral Dissertations

The adoption of conservation management practices is critical for improving soil health, enhancing nutrient use efficiency, and sustaining crop productivity in row crop systems in Louisiana. This study evaluated the role of conservation agronomic practices, soil biochemical indicators, and machine learning predictive models to improve soil nutrient dynamics, soil health indicators, microbial communities (MC), and crop productivity on a corn (Zea mays L.) research plot scale and in a commercial forty-hectare cotton (Gassypium hirsutum L.)-corn-soybean (Glycine max L.) rotation system in northeast Louisiana. The objectives of the study were to evaluate soil nutrient dynamics and MCs under …

Assessment Of The Bioremediation Potentials Of Biosurfactant-Producing Bacterial Strains Recovered From Spent Engine Oil-Contaminated Environments In Southwest Nigeria, Nafisa Mohammed Babayola, Nasiru Bright Lecky, Chinweizu Obioma Onumaegbu, Olufunmiso Olusola Olajuyigbe, Martins Ajibade Adefisoye

Journal of Environmental Science and Sustainable Development

Environmental pollution from hydrocarbons and their derivatives is predominantly of anthropogenic origin, occurring mainly during mining, transportation, and storage. This often in an annual release of substantial amounts of pollutants into the environment. The effective restoration of petroleum-contaminated environments requires a series of interventions to remediate soil to its natural state. This study aimed to isolate and characterize biosurfactant-producing bacterial strains with potential bioremediation capabilities to assess the potential application for remediating soils polluted with spent engine oil in the Remo district, Ogun State. Bacterial isolates were recovered from soil samples collected from spent engine oil contaminated sites, using standard …

Impacts Of Salinity On Microbial Enzyme Activity In Coastal Waters, Natali Ariyoshi

Honors Theses

Microbial extracellular enzymes are critical for the breakdown of organic matter and nutrient cycling in aquatic ecosystems. Extracellular enzyme activity serves as an indicator of nutrient turnover rates, metabolic states, and nutrient limitations within an ecosystem. Coastal ecosystems are especially dynamic as the influx of freshwater from inland runoff or seawater intrusion from storm surges can lead to fluctuations in salinity which can restructure microbial communities and alter enzymatic activity. Despite the ecological significance of these changes, few studies have explored the effects of short-term salinity shifts on microbial extracellular enzyme activity in coastal waters. This study investigated the effects …

Acquisition Behavior Response: Investigating The Ability Of Leptoglossus Phyllopus To Choose Between A “Good” Versus “Sub-Optimal” Strain Of Caballeronia, Irene L. Pham

2026 Spring Honors Capstones Projects

Leptoglossus phyllopus is a polyphagous pest that primarily feasts on citrus, tomatoes, and legumes. They must form a mutualistic symbiosis with Caballeronia every generation by ingesting the bacterium from their environment. However, not all species of Caballeronia confer the same fitness on the L. phyllopus host, raising the question of whether L. phyllopus possesses a partner choice mechanism that would allow it to distinguish between a good (GAOX1) and a suboptimal (Lep1P3) symbiosis partner. This was examined by conducting a choice experiment in which the two symbionts (GAOX1 vs. Lep1P3) were placed in a plastic box, and the bug’s roaming …

Bottles, Butterflies, And Biomass: Recycled Glass Sand, Microbial Additions, And Herbivory Effects On Milkweed Growth, Kealey Skinner

Honors Theses

Plant-soil-microbe interactions are integral components of ecological networks and drive ecosystem function from the bottom-up. Whereas herbivores regulate ecosystem function from the top-down, having opposing and potentially complementary effects on ecosystem function. My thesis sought to understand how below-ground microbial communities contribute to herbivore preference and plant biomass across varied soil substrates. My thesis asked: how do substrate and soil microbial communities influence herbivore preference and plant biomass accumulation on swamp milkweed (Asclepias incarnata)? To address this question, seedlings of A. incarnata were sown in 2.5 cm wide × 10 cm deep pots filled with either natural beach sand or …

Enrichment Of The Thermophilic Archaea Gearchaeales And Calditenuis In Lab Culture, Walter Saldivar

Electronic Theses, Projects, and Dissertations

Numerous microbes on Earth have yet to be grown in pure cultures and studied in the laboratory. Cultivation-independent genomic methods, such as metagenomics, can help us predict their metabolic capabilities, but cultivation remains valuable for testing these predictions. These uncultivated microbes are very diverse, especially within hot springs. Examples of these uncultivated microbes include the genus Calditenuis (formerly Aigarchaeota Group 1) and the order Gearchaeales; they are often abundant in terrestrial hot springs such as Great Boiling Springs (GBS) in Nevada. Previous work allowed for the establishment of laboratory enrichment cultures inoculated from sediments of GBS containing Calditenuis and …

Changing Dynamics Of Microbial Communities At A Hydrocarbon Contaminated Site And Methanogenic Interactions With Iron Minerals, Jakob Sell

Masters Theses

Microbial life is not only ubiquitous but also plays a critical role in the geochemical makeup of our planet. While researchers have long studied easily culturable aerobic microbes, the influence of anaerobic life on soils and mineral cycling is less understood. Notably, knowledge about interactions between anaerobic microbes and inorganic elements such as iron has progressed with the discovery that magnetite influences how anaerobic archaea carry out methanogenesis. To better understand anaerobic bacterial metabolisms and how they interact with minerals and subsurface hydrocarbons, we extracted 16S rRNA genes from two adjacent subsurface petroleum plumes, sequenced the DNA, and analyzed it …

Donor And Recipient Microbiome Interactions Determine Functional Outcomes Of Fecal Microbiota Transplantation For Clostridioides Difficile Infection, Sophie A. Millard

All Dissertations

Clostridioides difficile is a major cause of healthcare-associated diarrhea. Infection typically occurs after antibiotic treatment disrupts the gut microbiome, allowing C. difficile to colonize and produce toxins leading to disease (CDI). Standard antibiotic treatments can resolve acute infection but frequently lead to recurrence, highlighting the need for alternative strategies that restore the gut ecosystem. Fecal microbiota transplantation (FMT), the transfer of stool from a healthy donor, has emerged as an effective therapy for recurrent C. difficile infection (rCDI). Understanding the mechanisms underlying the success of FMT for treatment of rCDI could lead to safer, more defined microbial mixtures.

This dissertation …

Dried Water Treatment Residuals Might Be An Option To Reduce Soluble Reactive Phosphorus Release From Soils, Katie B. Mckay

Biological and Agricultural Engineering Undergraduate Honors Theses

Nonpoint source pollution from agricultural landscapes contributes to freshwater eutrophication, with legacy phosphorus (P) in soils potentially driving soluble reactive phosphorus (SRP) losses to surface waters. The objectives of this study were to evaluate SRP adsorption by dried water treatment residuals (WTRs) produced by Beaver Water District, quantify reductions in soil SRP release across increasing WTR application rates, and compare dried WTR performance to prior WTR studies.

Dried WTRs (~98% solids) were assessed using batch sorption experiments and soil core incubations. Phosphorus sorption was measured by mixing WTRs with CaCl₂ solutions containing increasing SRP concentrations and fitting results to …

Geographical And Anatomical Microbiome Variation In Invasive Green Iguanas (Iguana Iguana), Amanda A. Diaz

All HCAS Student Capstones, Theses, and Dissertations

The common green iguana (Iguana iguana) was introduced to South Florida in 1965 and has since been an especially pernicious threat both environmentally and economically. This highly invasive species is also expanding in range and populations at an astonishing rate. Understanding how this reptile is able to adapt and thrive in novel environments is of imperative need in order to begin managing their disruptive populations. Notwithstanding their negative impacts and significance, the microbiome of wild populations has not yet been characterized. Here, using 16S ribosomal RNA gene sequencing, this study is the first to characterize the microbiome composition …

Evaluating Elisa-Based Domoic Acid Detection Methods In Fetal And Maternal Samples Of California Sea Lions (Zalophus Californianus), Deanie Woodruff, Emily Lickiss, Samuel Gardiner, Mia Gastile, Elizabeth Sandoval, Florybeth La Valle

Seaver College Research And Scholarly Achievement Symposium

Harmful algal blooms produced by the diatom Pseudo-nitzschia regularly expose marine mammals along the California coast to domoic acid (DA), a neurotoxin that bioaccumulates in marine food webs. In California sea lions (Zalophus californianus), domoic acid exposure is associated with seizures, hippocampal injury, and maternal-fetal transfer of the toxin that can result in abortion. Bloom events have led to large numbers of stranded sea lions along the California coast. Although some clinical and neurological effects of domoic acid toxicosis have been documented, especially with regard to the hippocampus, there is limited understanding of how domoic acid concentrations fluctuate over the …

Biosensors For Biomedicine, Drake O'Leary

Miners Solving for Tomorrow Research Conference

This project investigated the use of engineered bacterial reporter systems to detect cellular stress responses associated with antibiotic activity. While constructs were successfully introduced and tested against known antibiotics, the reporter consistently produced a blue signal across conditions, limiting the ability to distinguish specific stress responses. This suggests issues such as leaky expression, insufficient regulatory control, or lack of specificity in the reporter design. Although results were inconclusive, this work highlights key challenges in developing reliable biosensors and provides a foundation for future optimization. Improving signal specificity and reducing background expression will be critical for enabling accurate characterization of antibiotic …

Ecovoltaic Solar Energy Development Creates Novel Microclimate, Temperature, And Soil Moisture Patterns Under Solar Panels In A Warm Desert, Juan Pinos, Seth M. Munson, Claire C. Karban, Matthew D. Petrie

Life Sciences Faculty Research

Background As solar energy development expands in desert regions, new installation practices and solar technologies seek to balance ecosystem conservation and energy generation (ecovoltaics). The Gemini Solar Project, a large ecovoltaic facility located in the northeastern Mojave Desert, employed low impact installation methods to reduce disturbance of the desert ecosystem within arrays of bifacial panels mounted on solar tracking systems. We evaluated microclimate and environmental conditions across five locations: four within-facility microsites (underneath solar panels, east and west panel driplines, and interspaces between panel rows) and one in the undisturbed desert outside the facility. Results Under panel microsites experienced lower …

Sustainable Mitigation Of Microplastic Pollutants Using Native Plant Species, Antonio De Jesus Martinez De La Rosa, Emily Lancaster

Research Papers

Microplastics (MPs) are defined as small plastic particles that come from the degradation of plastics [Ziani et al. 2023], that hold a regular or irregular shape, ranging from 1μm to 5 mm [Campanale et al. 2025]. This diminutive size makes them virtually impossible to remove once released into the environment[Lee et al. 2023]. Furthermore, biological, chemical, and physical processes break MP's further down in the environment, causing them to exist in nano-level sizes (1nm-1μm) [Lee et al. 2023], further exacerbating their threat to critical habitats. However, recent studies have shown MP contamination expands beyond the natural environment as recent studies …

Assessing The Influence Of Temperature And Water Level On Gill Disease In Goldfish, Moses Elijah Cadawas, Emmalie Turner, Darlene Panvini

SPARK Symposium Presentations

Gill disease in fish is a strong biological indicator of water quality and environmental stress. These diseases are commonly caused by bacterial or parasitic infections that target gill tissues and can lead to severe physiological impairment and ultimately mortality. Several environmental factors, including water level and temperature, play a critical role in determining fish susceptibility to these infections. Changes in these conditions can act as stressors that weaken immune defenses and promote pathogen proliferation. This study aimed to evaluate the relative impact of environmental stressors on the development of gill-associated disease in Carassius auratus (goldfish) under controlled conditions. Following exposure …

Imidacloprid Effects On The Survival And Cutaneous Microbiome Of Northern Leopard Frogs, Evelyn Margaret Osterloo

Honors Thesis

Amphibians are experiencing population declines due to habitat loss, climate change, and diseases, particularly chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis. Protection from this fungal infection stems from the cutaneous microbiome. Pesticides have been shown to affect amphibians in a variety of ways, including reducing survival, locomotor performance, and accumulation in body tissues. Pesticides may also lead to changes in the cutaneous microbiome affecting amphibians who rely on these organisms as an anti-Bd defense mechanism. To investigate the effect of imidacloprid, a neonicotinoid insecticide, Northern Leopard frogs (Lithobates pipiens) were subjected to sublethal concentrations (control = …

Enhancing Urban Garden Capacity By Linking Biodiversity And Ecosystem Function, Mary T. Nguyen, Carleen Rauh, Shelby Gresch, Charlotte Correiro, Heidi Elmendorf, Adriane Fugh-Berman, Gina Wimp, Alexandra L. Decandia

Virginia Journal of Science

Urban agriculture broadly describes food and plant cultivation in metropolitan areas. While biodiversity is thought to support ecosystem health and resilience, the relationship between above-ground and below-ground diversity has been understudied in urban green spaces. This study examines plant, animal, bacterial, and fungal diversity across three distinct urban habitats: a turf lawn, a forb garden, and a farming space. Using bacterial 16S rRNA and fungal ITS2 sequencing, soil nutrient analyses, and surveys of vegetation and wildlife, we connect diverse philosophies in urban agriculture to their role in advancing community diversity and ecosystem function. We found that different urban gardens support …

Methane Consumption Rates By Coastal Virginia Beach Microbes, James R. Bailey Ii

Knowledge and Creativity Expo

This study measures whether microbial communities in the shallow coastal waters of Virginia Beach are capable of consuming methane in the water column. Using methane enrichment incubations and gas chromatography, we found no measurable methane oxidation of our samples over multi-day periods. These results suggest that these coastal waters may act as net sources of atmospheric methane.

Impact Of Legacy Amf Communities On Vegetative Growth & Yield Of Soybean, Dylan Habeeb, Connor Morozumi, Natalie Christian

The Cardinal Edge

Soil microbial communities are increasingly recognized as an important factor in sustainable agriculture. Arbuscular mycorrhizal fungi (AMF), are key players in these communities, known to benefit their plant host in a number of ways, such as increased nutrient uptake. Plants can partner with multiple AMF species; however, little is known about how interactions between multispecies communities of AMF impact plant growth and yield. In an agricultural setting, the long-term development of these communities following practices such as rotational planting or cover cropping is also an important consideration, but there is little research on the long-term legacy of AMF communities or …

Seasonal Dynamics And Trends Of Environmental Conditions In Lake Louise, Georgia, Daniel Kwawuvi, James A. Nienow

Georgia Journal of Science

Lakes are important aquatic ecosystems that are extensively influenced by seasonal variations. In this study we investigate the seasonal dynamics and trends of three environmental variables, water temperature, conductivity and dissolved oxygen (DO), in Lake Louise, a sinkhole lake located in southern Georgia. These variables were measured in-situ along a depth profile from January 27, 2024 to January 17, 2025. We also accessed archived data from field campaigns in 2003, 2004, and 2017 in order to test whether a recent increase in the number of hurricanes impacting the region, five since August, 2017, may have significantly altered the seasonal dynamics …

Biofilm Architecture Determines Proliferation Of Phages And Plasmids, James B. Winans

Dartmouth College Ph.D Dissertations

This thesis explores how biofilm architecture determines the spread and ecological consequences for the bacteria-dependent genetic elements phages and plasmids. Using Escherichia coli and Vibrio cholerae as model microbes, and the genetic elements T7 phages, λ phages, and conjugative plasmid pED208, we investigate how spatial structure influences phage infection dynamics, plasmid transfer, and interbacterial interactions within biofilms. We show that densely packed biofilms can protect sensitive bacteria from phage exposure and modulate competitive outcomes between obligately lytic and temperate phages. We find that entirely different outcomes can coöccur within microns of each other dependent on biofilm structure. We also demonstrate …