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 …

Enhancing Salinity Tolerance In Black Soybean Genotypes Through Synergistic Rhizobacterial Inoculation, Fairus Hisanah Hibatullah

Scholars Week

Soil salinity is a major environmental constraint that limits soybean productivity by disrupting plant growth, nutrient uptake, and biological nitrogen fixation. Beneficial microorganisms have emerged as a sustainable approach to improve crop tolerance to saline conditions. This study aimed to identify the most salt-tolerant black soybean phenotype and evaluate the individual and combined effects of symbiotic nitrogen-fixing bacteria (SNFB) and plant growth-promoting rhizobacteria (PGPR) under salinity stress. This study consisted of two stages, the first identified the most salt-tolerant black soybean phenotype (BS 87, BS 99, and BS 114), and the second evaluated the effects of symbiotic nitrogen-fixing bacteria, plant …

Bioactive Potential Of Microbial Isolates From Yoluja Cave And Jepirramüin Rock Shelter, Cabo De La Vela (Colombia), Juan Sebastián López Caro, Virginia Patricia Roa Angulo, Alex Alberto González Vargas

International Journal of Speleology

Subterranean environments harbor diverse microbial communities with significant potential for the production of bioactive compounds. This study evaluated the antimicrobial and antioxidant potential of microbial isolates obtained from Yoluja Cave and the Jepirramüin rock shelter, located in the coastal region of La Guajira, Colombia. Field sampling was conducted during three campaigns in July, September, and November 2025, including soil and surface samples collected along environmental gradients within each site. Microorganisms were isolated using selective culture media and identified through morphological and biochemical characterization. Selected strains were subjected to liquid fermentation and organic solvent extraction to obtain crude metabolites. Analysis of …

The Relationship Between Light Intensity And Tall Goldenrod Productivity Across Greencastle Fields, Erniya Jean Jacques '29, Rose Keith

Annual Student Research Poster Session

This study investigates the effects of environmental conditions, specifically light availability and climate variation, on the growth and productivity of Solidago altissima (tall goldenrod) across four field sites in Greencastle, Indiana (including sites associated with DePauw University, such as Prindle, Ullem, QA, and NP). By sampling 160 specimens across contrasting light environments (sunny vs. shaded plots) and comparing data between 2024 and 2026, the project evaluates key physical traits including plant height, biomass, and light intensity (μmol). Findings indicate a trade-off in energy allocation: plants in shaded conditions invest more energy into height growth to capture limited sunlight, whereas individuals …

Building Genetic And Culturing Tools For The Understudied Soil Bacterium E. Flagellatus, Aaron Butler, Brenda Pratte, Lon Chubiz

Undergraduate Research Symposium

Soil bacteria play essential roles in nutrient cycling, yet many abundant groups remain poorly characterized due to challenges in cultivation and genetic manipulation. One such organism is Edaphobacter flagellatus, a member of the Acidobacteriota frequently detected in soil environments but lacking well-developed experimental tools. To address this limitation, our laboratory has generated a genome-wide mutant library using the Tn5 transposon, enabling random disruption of genes across the population.

This project aims to establish culture conditions necessary to support the use of this library for functional genomic studies. In particular, defined minimal media can impose selective pressures that reveal …

Temporal Variation In Picophytoplankton Pigment Phenotypes Of Two Urban Rivers, Kylee M. Lamberson, Camille E. Wendlandt, Kristin E. Forgrave, Anne W. Thompson

International Journal of Undergraduate Research and Creative Activities

Picophytoplankton are a group of photosynthetic, unicellular organisms, making them key primary producers in aquatic ecosystems. These cells numerically dominate in oceans and lakes where picophytoplankton communities contain phenotypic subpopulations that correspond to biogeographic patterns. In rivers, however, such community dynamics are less studied. We examined the phenotypic subpopulations of picophytoplankton in two converging urban river environments of Portland, Oregon (USA): the Columbia and the Willamette Rivers. From September 2022 through July 2023, we took roughly bi-weekly surface water samples and used multi-laser flow cytometry to distinguish between photosynthetic cells based on their size and pigment fluorescence. We discovered seven …

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 …

Asm And A Culture Of Sharing, Caring, And Fun In Education, David J. Westenberg

Biological Sciences Faculty Research & Creative Works

One doesn't always equate a professional scientific society with sharing, caring, and fun, but in this age of public distrust, public engagement with science and active student learning are ways to regain trust. ASM holds a leadership position in promoting and recognizing the value of education in the future of our profession and is there to support your educational journey. From K12 outreach and public engagement, to professional development, to presenting and publishing scholarship of teaching and learning, ASM has been at the forefront of biology education. Under the leadership of visionary directors such as Amy Chang and now Irene …

Evaluating Pfas And Marine Microbial Interactions In Estuarine Sediments With Varying Urbanization And Assessments Of Microbial Responses To Pfos, Zachary J. Padgett

All Theses

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of synthetic chemicals that have become globally distributed due to their extensive use in industrial and consumer products and their extraordinary resistance to environmental degradation. Their persistence and documented toxicity have made them a growing concern in coastal environments, particularly in estuaries where urban runoff, wastewater, and industrial discharges concentrate these compounds. Estuaries are unique in that tidal mixing and interactions with fine-grained sediments and organic matter promote PFAS retention, while the microbial communities living directly within estuarine sediments are positioned where PFAS preferentially accumulate, creating conditions for prolonged exposure and …

Understanding The Potential Sources Of Bacteria And Turbidity Pollution In The Edisto Island Watershed, Brynne Sumner

All Theses

Anthropogenic pollution introduces contaminants, such as pathogenic bacteria and turbidity, into coastal watersheds. These contaminants are the major contributors to water quality impairments in the three sub-watersheds encompassing Edisto Island and the Town of Edisto Beach (hereafter referred to as the Edisto Island Watershed), located within the ACE Basin, South Carolina, USA. With 18 locations impaired for fecal bacteria and 19 for turbidity on the 2024 South Carolina 303(d) list of impaired waters, the Edisto Island Watershed offers valuable insights into the water quality challenges rural coastal communities face.

This study aimed to identify the sources of fecal bacteria and …

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 …

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 …

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 …

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 …

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 …