Microbiology Commons^™

Combating Antibiotic Resistance With Plasmid-Dependent Phages, Rhiannon T. Mariano

Electronic Theses & Dissertations (2024 - present)

The alarming rise of carbapenem-resistant bacteria poses an urgent global health threat, driven in large part by the horizontal spread of carbapenemase-encoding plasmids (Ma et al., 2023). These plasmids are often highly mobile and transmissible, enabling rapid dissemination of resistance genes across diverse bacterial populations. Their mobility is largely mediated by conjugation, a process dependent on the formation of pili, which serve as physical bridges for plasmid transfer between cells (Murray et al. 2022; San Millan and MacLean 2017; Virolle et al. 2020). Beyond their role in gene exchange, these pili also act as entry points for a unique class …

The Influence Of Localized Water Quality On Eastern Oysters (Crassostrea Virginica) And Their Internal Microbiome Under Changing Environmental Conditions, Jessie Rivera Lafreniere

College of Graduate Studies: Theses & Dissertations

Oysters are found ubiquitously in estuaries along the Georgia coast, where marsh morphology and large daily tidal fluctuations create dynamic and stressful conditions to which oysters may be locally adapted. Based on water quality data from the Sapelo Island National Estuarine Research Reserve, it is evident that changing climatic conditions are rapidly causing shifts in water quality that may be adversely affecting oyster health, especially as ocean acidification alters the carbonate buffering capacity, increasing the amplitude of daily pH variations. Importantly, the rate of change of conditions are not uniform within estuaries, varying on spatial and temporal scales. The symbiotic …

The Coral Microbiome Under Climate Change: Shifting Symbiotic Interactions, Katherine E. Parker, Kate M. Quigley

Biological Sciences Faculty Publications

Host–microbe symbioses are central to organismal health, yet these complex partnerships are often strongly shaped by the environment. Climate change is increasingly altering environmental conditions, disrupting the balance of host–microbe interactions and pushing them along a continuum from mutualism (both partners benefit) toward parasitism (one partner gains at the other’s expense). Reef-building corals provide a clear example of this vulnerability, as the coral holobiont, an ecological unit comprising diverse photosynthetic algal symbionts (Symbiodiniaceae) and other microbial partners, depends largely on these mutualistic interactions for nutrition, immunity, and stress tolerance. Increasingly, evidence suggests that under heat stress, the algal symbionts retain …

Population Genomics And Evolution Of Pseudomonas Aeruginosa, Samara T. Choudhury

Electronic Theses & Dissertations (2024 - present)

Pseudomonas aeruginosa is a Gram-negative bacterium ubiquitous in diverse environments and an opportunistic pathogen in humans. It is a leading cause of chronic lung infections in cystic fibrosis patients and of hospital-acquired pneumonia and sepsis. With a large flexible genome and abundant mobile genetic elements, P. aeruginosa exhibits high levels of antimicrobial resistance (AMR), making it a significant public health threat. Evolutionary processes such as homologous recombination, and horizontal gene transfer generate extensive genomic diversity in this species and facilitate the spread of resistance genes. In this dissertation, I investigate the genetic and evolutionary factors shaping P. aeruginosa population structure …

Interaction Of The Gram-Positive Human Pathogen Staphylococcus Aureus With Host Lipids, Sharanya Paul

Theses and Dissertations

Staphylococcus aureus is a prominent pathogen that is known to incorporate straight-chain unsaturated fatty acids (SCUFAs) into its lipids in addition to the normally biosynthesized branched-chain fatty acids (BCFAs) and straight-chain fatty acids (SCFAs). Furthermore, it has recently been shown that the incorporation of oleic acid into S. aureus lipids significantly enhanced the growth of the organism at low temperatures due to the greater fluidity imparted to the membrane. Together with others in the Wilkinson and Dahl laboratory, I have shown that low-temperature growth is enhanced by various SCUFAs, including the human antimicrobial fatty acids sapienic acid, linoleic acid, and …

Quantifying Amendment Impact On Microbial Respiration Rate, Qwynn Starrwalker

Honors Undergraduate Theses

Wetlands play a critical role in the global carbon cycle by acting as carbon sinks, where the flooded anaerobic conditions cause slow microbial respiration compared to other soils. Comparatively more carbon is stored in the soil as organic matter than is released as carbon dioxide (CO₂). Making wetland pools of soil organic matter less available to microbes for respiration could reduce overall atmospheric CO₂ and slow global warming. This study examined the effect of kaolinite, goethite, and lime on microbial respiration rates in wetland soils under alternating hydrologic conditions. Homogenized soil from a cypress dome was separated …

Carbaryl Exposure Alters Gut Microbiome Composition Without Affecting Morphometrics In Eastern Purple Martin (Progne Subis Subis) Nestlings, Stephanie A. Gaspar

Graduate Studies Theses and Dissertations 2026

Eastern purple martins (Progne subis subis) rely entirely on human-provided nesting structures throughout their breeding range in eastern North America. To control haematophagous mites that commonly infest these nests, many landlords apply the carbamate insecticide, carbaryl. Although effective at reducing ectoparasite populations, carbaryl exposure may have unintended effects on the gut microbiome, growth, and condition of developing birds. This study examined the effects of carbaryl exposure on gut microbial communities and morphometric condition in wild nestlings. Nests were experimentally treated with carbaryl, and nestling morphometrics and fecal microbiomes were compared between treated and untreated groups at 18 days …

Regulation And Localization Of Urease In Sporosarcina Pasteurii: Implications For Coastal Protection, Amar Kosovac

UNF Graduate Theses and Dissertations

Coastal erosion is a persistent problem exacerbated by global warming. As the climate changes, the southeastern coast is likely to experience an increased frequency and intensity of storms, which can significantly damage the coastline. The coast is crucial as it serves as a habitat for numerous animals, supports tourism, and underpins infrastructure. Microbially induced calcite precipitation (MICP) is a novel method to enhance erosion resistance in sandy soils using the non-pathogenic bacterium Sporosarcina pasteurii. S. pasteurii produces urease to catalyze urea into bicarbonate, which drives the precipitation of calcium carbonate. Maximal expression of urease is a limiting factor for …

Interactions Of Complement With Paramyxovirus Persistently Infected Cells, Nasser N. Yousef

Graduate Studies Theses and Dissertations 2026

Persistent RNA virus infections (PI) are often characterized by extended viral shedding and maintained cycles of inflammation. We have an incomplete understanding of interactions between exogenous and cell intrinsic Complement (C') factors and paramyxovirus PI cells. Parainfluenza virus 5 (PIV5) acute infected (AI) cells can be recognized and lysed by exogenous C’ factors, but PI cells become resistant to C’-mediated lysis. We hypothesized that the relative sensitivity of AI and PI cells to C’ lysis is correlated with viral glycoprotein expression on the surface of cells. PI cells display lower levels of viral glycoprotein expression compared to AI cells. Pharmacological …

Investigating The Anti-Apoptotic Properties Of The N-Terminus Of The Chlamydia Trachomatis Effector Tarp, Kasey S. Jordan

Graduate Studies Theses and Dissertations 2026

As the most prevalent bacterial STI in the United States and leading cause of infection-related blindness worldwide, the obligate intracellular bacteria, Chlamydia trachomatis (Ct), poses a significant threat to public health. As an obligate intracellular bacteria, invasion of the host cell is a crucial step in Chlamydia’s developmental cycle. To drive invasion, Ct injects prepackaged effectors into the host cell using a T3SS. An early Chlamydial effector, translocated actin recruiting phosphoprotein, or Tarp, interacts with host cell actin to promote invasion, mediated via Tarp’s C-terminal region. Although the function of Tarp’s C-terminus is well defined, the Tarp’s N-terminus …

Viral And Host Cell Determinants Of Resistance To Complement-Mediated Killing During Parainfluenza Virus Type 5 Infection, Jenna R. Aquino

Graduate Studies Theses and Dissertations 2026

RNA viruses are a major global public health concern due to high mutation rates, zoonotic potential, and immune evasion. Parainfluenza virus 5 (PIV5) can establish persistent infections (PIs) despite encountering innate immune responses, including the complement (C′) system. RNA virus replication produces defective interfering particles (DIPs) containing truncated defective viral genomes (DVGs) that depend on standard (STD) virus for replication. DVGs are increasingly detected in natural infections and modulate type I interferon (IFN-I), but their role in the C′ system is unclear. We investigated how DVGs affect C′-mediated lysis during PIV5 infection using real-time in vitro cell viability assays. C′ …

Targeted And Screening Based Approaches To Analyze Drm Transcriptional Repressor Complex Activity In Caenorhabditis Elegans, Emily Washeleski

Dissertations, Master's Theses and Master's Reports

The molecular machinery that control the eukaryotic cell cycle, specifically the processes that mediate the switch between cellular division or quiescence, are essential for cellular and organismal viability. However, how the same machinery integrates with developmental or differentiation programs is less well understood. In Caenorhabditis elegans, the 8-subunit DRM complex (for Dp, Rb and MuvB), whose subunits belong to the Synthetic Mulitivulva (SynMuv) B class genes, is a central regulator of the cell cycle but also prevents inappropriate cell fate specification. The conserved mammalian DREAM complex (for Dp, Rb, E2F, And MuvB) is best known as a transcriptional repressor …

Bacterial Community Function In Pitcher Plant Leaves As An Experimental And Mathematical Model Of Functional Dynamics, Amelia Jackson

Cal Poly Humboldt theses and projects

This work looks at two different sites with differing abiotic factors in measures of altitude, temperature and precipitation. The site with higher altitude, larger temperature range, and lower precipitation, located in Plumas National Forest (Quincy, CA), had a flat BEF trend that suggests functional redundancy The site with lower altitude, more moderate temperatures, and higher precipitation located in Six Rivers National Forest (Gasquet, CA), also had a flat BEF trend. These abiotic factors could correlate to the significantly different bacterial compositions between sites. The second portion of this work is modeling the host antagonist relationship between Eyxra moths and their …

Surveillance Of A Novel Vesivirus Discovered In An Urban Mephitis Mephitis Population, Amanda E. Diggins

Honors Theses and Capstones

Caliciviridae is a family of non-enveloped, positive-sense, single stranded RNA viruses, including eleven defined genera that contain important pathogens of humans and animals. Within the Caliciviridae family, the genus Vesiviridae includes feline calicivirus, a leading cause of upper respiratory disease in cats, and vesicular exanthema of swine virus, a historical disease of domestic swine that has now been implicated in several marine mammal vesicular diseases, one of which has been confirmed zoonotic. Urban landscapes create a unique environment for rapid intra- and interspecies transmission of viruses. Clustered resources attract high-density populations of synanthropic wildlife species, increasing spatial overlap and heightening …

Exploring Biopsychosocial Influences On Hookup Culture And Disrupting Compulsory Behaviors In Emerging Adults: A Multidisciplinary Analysis Of A Contemporary Public Health Concern, Catherine Benjamin

Honors Theses and Capstones

Multidisciplinary analysis, including biology, psychology, and sociology, to better understand the compulsory Hookup Culture that exists as a contemporary public health concern among the age group defined as emerging adults. Sexually Transmitted Infections (STIs) diagnoses are steadily rising in the United States and disproportionately affecting college students. Early socialization and current educational resources that contribute to shame and stigma are discussed to explain how lifestyle and social conditions can act as risk factors for individual health outcomes.

Effects Of Volatile Organic Compounds Produced By Temperature-Adapted Microbes On Duckweed Growth, Phaedra Yael Stemp

Honors Theses and Capstones

As host-associated microbes adapt to their abiotic environment, these adaptations can affect their host species as well. Previous research showed that varying temperatures and volatile organic compound (VOC) production can affect microbial benefits to hosts. This experiment analyzed how 27 microbes pre-adapted to different temperature conditions affected growth of their host, common duckweed plants, comparing effects of direct contact with microbes, effects of microbe VOCs alone, or both. Each microbe was pre-adapted to one of three temperature regimes: “Northern” at 28 °C, “Southern” at 33 °C, and “Extreme” at 36 °C. We then grew duckweeds in I-plates with each microbe …

Investigating Microbe-Mediated Temperature Tolerance In Lemna Minor, Matthew Thomas Farbaniec

Honors Theses and Capstones

Temperature limits plant growth and survival more than many other environmental variables, and increases in the frequency of extreme hot or cold weather events pose significant challenges for plant growth and crop yields. Previous studies have shown that bacteria, fungi, and other microorganisms associated with plants ( i.e., the plant microbiome) can influence host response to temperature stress. These same microbes have their own temperature tolerances. We investigated whether microbial temperature tolerance correlates with plant resilience using an aquatic plant model, Lemna minor, and isolates derived from its microbiome. Microbial isolates were assessed at −10°C, 4°C, and 32°C for …

Development Of Shigella Flexneri Detection Method By Real-Time Polymerase Chain Reaction Targeting The Sfmd Gene, Muktiningsih Nurjayadi, Puan Aqila Azizah, Agus Setiawan, Ananda Indah Putri Sihombing, Anisa Fitriyanti, Grace Grace, Gusti Angieta Putri, Helzi Angelina, Royna Rahma Musie, Jefferson Lynford Declan, Gladys Indira Putri, Dandy Akbar Juliansyah, Siti Fatimah, Tiara Fahriza, Irma Ratna Kartika, Fera Kurniadewi, Novitasari Novitasari, Bassam Abomoelak, Hesham Ali El Enshasy, Shyi-Tien Chen

Makara Journal of Science

Shigella flexneri can cause shigellosis, which results in high fever, vomiting, diarrhea, or death. This study developed a detection method based on real-time polymerase chain reaction that targets the sfmD gene of S. flexneri given that the virulence factor encoded by this gene is thought to facilitate adhesion to a host surface. The proposed method involves primer design, DNA isolation, the optimization of primer annealing temperature, and confirmation, specificity, and sensitivity tests. A sfmD primer with an amplicon length of 155 bp was annealed to the target DNA at an optimized temperature of 60 ℃ (range 54 °C–62 °C). This …

Seroprevalence And Risk Determinants Of Toxoplasma Gondii Infection In Pregnant Women In Pakistan: A Cross-Sectional Study, Tajul Haram, Kamran Khan

Journal of Bioresource Management

Toxoplasma gondii is a globally important zoonotic parasite, and maternal infection during pregnancy may cause miscarriage, congenital anomalies, or severe neonatal complications. This cross-sectional study was conducted among 367 pregnant women attending hospitals in District Dir Upper, Khyber Pakhtunkhwa, Pakistan, to evaluate the seroprevalence of T. gondii and associated risk factors. Blood samples were analyzed using Immunochromatographic Test (ICT) for initial screening, and positive cases were confirmed by Enzyme-Linked Immunosorbent Assay (ELISA). Overall, 34.6 % (127/367) of women tested positive. While no significant differences were observed across age groups, gestational trimesters, or abortion history, higher prevalence was noted in women …

Straw Cover Increases Garden Soil Microbial Biodiversity, Emory Walker, Mara Welty, Emma Creviston

The Journal of Purdue Undergraduate Research

No abstract provided.

A Comparison Of White-Light And Monochromatic Led Sources For Antimicrobial Photodynamic Inactivation Of Staphylococcus Aureus, Emily Simmons

The Journal of Purdue Undergraduate Research

Drug-resistant bacteria are an ongoing public health crisis for which alternative treatments are needed. One alternative is antimicrobial photodynamic inactivation (aPDI), which uses potent photosensitizers and light irradiation to damage the bacteria. Our standard light source used in aPDI is a single-wavelength light source at 405-nm; however, we evaluated a white-light source for similarities in the resulting aPDI activities. This is done by comparing aPDI experiments using S. aureus and its methicillin-resistant strains (MRSA) conducted with either the white LED light source or the 405-nm LED light source. Statistical analysis using t-tests revealed no significant differences in the aPDI activities …

Development Of Broadly Protective Vaccines Against New World Arenaviruses, Brian B. Gowen

Funded Research Records

No abstract provided.

Effects Of Supplemental Led Lighting And Biofertilizer On Yield And Fruit Quality Of Japanese Strawberry Cultivars In Indonesia, Reginawanti Hindersah, Febby Fitriyani, Kenji Endo, Masakazu Nakayama, Syariful Mubarok, Gita Bina Nugraha

Jurnal Kultivasi

Growing strawberries in soilless substrates in the greenhouse relies on fertilizers and supplemental light to boost yield and fruit quality. The research evaluated the properties of the biofertilizer and its effectiveness on the yield of Japanese strawberry cultivars Nanatsuboshi and KS-75 under controlled greenhouse conditions, with and without light-emitting diodes (LED) as supplemental light. The cell viability and plant-growth-promoting properties of a liquid consortium biofertilizer consisting of nitrogen-fixing bacteria and phosphate-solubilizing microbes, were characterized. Laboratory analysis confirmed the biofertilizer's composition, and a greenhouse experiment using a completely randomized design tested treatments of biofertilizer, LED, and their combination. The biofertilizer contained …

Effects Of Integrated Biological And Chemical Fertilization On Pecco And Banji Shoot Development In Tea Plants, Intan Ratna Dewi Anjarsari, Muhammad Raihan Abdillah Farros, Santi Rosniawaty

Jurnal Kultivasi

Tea productivity and quality are largely determined by shoot structure, particularly the balance between pecco shoots (tender buds and young leaves) and banji shoots (older, less productive shoots). Conventional reliance on inorganic fertilizers often enhances overall growth but does not necessarily improve shoot structure, while biofertilizers alone provide limited nutrient availability. This study aimed to evaluate the effects of combining microbial-based liquid biofertilizers with inorganic fertilizers on the structure of tea shoots. The experiment was carried out on seed-derived tea plants using a randomized block design with several fertilization treatments, including sole biofertilizer, sole inorganic fertilizer, and their combinations. The …

The Effects Of Nanobubble Fertigation And Soil Conditioners To Improve Nutrient Dynamics, Soil Microbial Activity, And Chili Productivity, Betty Natalie Fitriatin, Euis Ahah Rokayah, Elsa Naila Elmyra, Tualar Simarmata, Nicky Oktav Fauziah, Hanif Fakhrurroja

Jurnal Kultivasi

Drip fertigation is a fertilization method that integrates nutrient delivery with an irrigation system, which is capable of optimizing the direct delivery of nutrients to the root zone. This experiment aims to investigate the effect of drip fertigation with nanobubble technology, and soil conditioners on the population of Phosphate-Solubilizing Bacteria (PSB) and Azotobacter spp., available phosphorus, total nitrogen, growth, and yield of red chili. The study used a Strip Plot Design with two factors and three replications. The first factor was nutrient application (solid NPK fertilizing as control; drip fertigation; and drip fertigation with nanobubble technology), and the second factor …

Role Of Cellular Stress Responses In Innate Immune Defense Against Acute Respiratory Infections, Amit Sharma

LSU Doctoral Dissertations

The endoplasmic reticulum (ER) stress sensor inositol-requiring enzyme 1α (IRE1α) is an important regulator of innate immune cells. However, its role in pulmonary innate host defenses remains poorly understood. This dissertation elucidates the dual, context-dependent role of IRE1α in host defense against methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. We demonstrate IRE1α’s function as both a detrimental mediator of acute pathology and an essential facilitator of innate immune memory. Our work revealed that acute IRE1α activation during primary MRSA infection is detrimental. In lungs and alveolar macrophages (AMs), IRE1α is activated in response to MRSA infection. Consequently, IRE1α activation triggers a hyperinflammatory …

Microplastic Exposure Alters Tubulin Leading To Alterations In Insulin Secretion By Pancreatic Beta Cells, Anakaren Garcia

Honors Program Theses and Research Projects

Abstract

Diabetes mellitus is a metabolic disorder characterized by elevated blood glucose levels due to impaired insulin secretion or diminished cellular response to insulin (resistance). Pancreatic β-cells depend on a well-organized cytoskeleton, particularly microtubules composed of α- and β-tubulin heterodimers, to transport insulin granules to the plasma membrane during glucose-stimulated insulin secretion (GSIS). Disruption of microtubule organization can impair granule trafficking and reduce insulin release. However, emerging environmental toxicants such as microplastics that interfere with β-cell cytoskeletal function remains largely unexplored.

Microplastics (MPs) are small plastic particles (< 5 mm) that have become widespread environmental contaminants and can enter biological systems. Previous studies have shown that MPs can induce cellular stress and protein misfolding, but their effects on microtubules in pancreatic β-cells are not well characterized. This study investigates whether exposure to fluorescent polystyrene microplastics alters microtubule organization and insulin secretion in βTC-6 cells.

βTC-6 cells were treated with 10 µg/mL of fluorescent polystyrene microplastics for …

Exploring The Role Of Faecalibacterium Prausnitzii Metabolites In Modulating Fatty Acid Metabolism And Protecting Hepg2 Cells During Induced Steatosis, Morgan Martin, Emerald Cole

Student Scholar Symposium

The obesity epidemic has risen to astronomical numbers with over 650 million adults being classified as obese (BMI≥30). Obesity is of critical concern as excess body fat storage is a comorbidity to various diseases including type-2 diabetes, cardiovascular disease, and cancer. Although obesity has classically been attributed to genetics and unhealthy lifestyle choices, there is a growing interest in other factors affecting obesity, including the gut microbiome. For example, mice lacking a microbiome are resistant to weight gain even when placed on a high-calorie diet. It can then be concluded that bacteria and the metabolites they produce can dramatically affect …

Advancing Louisiana's Cropping Systems: Sustainable Bioenergy Production, Cover Crops, And Technology Integration, Pedro R. Carrillo

LSU Doctoral Dissertations

The adoption of cover crops in Louisiana is lower than the national average, underscoring the need for region-specific research to address environmental challenges and demonstrate the short-term benefits of these practices within existing production systems. This research evaluated the integration of cover crops (CC) in energy cane (Saccharum spp.) and no-till cotton systems, focusing on their effects on soil health, nitrogen (N) management, and biomass production. Soil health indicators (SHIs), including enzymatic activities (β-glucosidase, β-glucosaminidase, and urease), protein N, inorganic N concentrations (nitrate and ammonium), soil organic matter (SOM), and microbial community composition assessed through ester-linked fatty acid …

Ecology Of Subaerial Algae: Photosynthetic Capacity As A Function Of Relative Humidity In A Naturally- Occurring Association, James A. Nienow

Georgia Journal of Science

Subaerial algae are defined by their ability to grow on surfaces exposed directly to the air. We are currently investigating the nature of the adaptations that allow these unicellular microorganisms to form rich growths in an environment subjected to repeated and prolonged periods without liquid water. It is well known from laboratory studies that at least some members of the group are able to sustain metabolic activity using water vapor at high relative humidity. However, data concerning the significance of this ability in natural populations are almost completely lacking. To help fill in this gap, we tracked the photosynthetic capacity …