Microbiology Commons^™

Analysis Of The Atypical Temperature Dependence And Conformational Changes During Turnover Of A Lactobacillus Chlorogenic Acid Esterase, Nathaniel Carl, Yianni Tsigaris, Dan Ji, Nora K. Anpree, Kellie K. Omori, Cedric P. Owens

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Many bacterial chlorogenic acid esterases (ChlEs) exhibit atypical temperature behavior, featuring activities that barely change with temperature and activity maxima that fall below the thermal denaturation point. This work focuses on a ChlE from Lactobacillus helveticus (Lh–ChlE), which has a flat temperature dependence. First, it was determined that conformational changes during Lh–ChlE turnover are not rate-limiting and that the overall rate depends on the chemical step at all temperatures. Next, Lh–ChlE’s temperature dependence was investigated using a conformational equilibrium model that assumes the existence of a temperature-dependent equilibrium between an active and an inactive conformation and an activation heat capacity …

Immunomodulatory And Signaling Molecules From Plant-Associated Bacteria: Toll-Like Receptor 4 Agonist Adjuvants And Diketopiperazine-Mediated Communication, Marian Romaine

Dissertations, Theses, and Capstone Projects

Medicinal plants and their associated microbiomes constitute a rich source of bioactive natural products with applications in immunotherapy and microbial ecology. Herbal formulations have long been valued for safe immune enhancement, while bacterial signaling molecules govern community behaviors critical to pathogenesis, symbiosis, and environmental processes. Bacterial lipopolysaccharides (LPS) from plant-associated Gram-negative bacteria have emerged as potent TLR4 agonists, yet their endotoxic potential limits direct use, and diketopiperazines (DKPs) serve as versatile quorum-sensing mediators capable of modulating biofilms in mixed microbial systems.

The work in this thesis comprises two independent but complementary research strands. The first strand pursued the engineering of …

Skin Of Frog And Scale Of Dragon: Nutritional Cues, Life Cycle Kinetics, And Secretome Dynamics In Batrachochytrium Dendrobatidis, Naomi C. Okada

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nearly 50% of amphibian species are at risk of extinction, making them the most threatened group of vertebrates on the planet. A major driver of these declines is the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes the fatal skin disease chytridiomycosis. Since its discovery in the late 1990s, Bd has been directly implicated in the extinction of 90 species of amphibians and the declines of hundreds more. Despite this devastating ecological impact, relatively little is known about its basic cellular biology.

Bd has a multi-stage asexual life cycle consisting of a motile and infectious zoospore, which encysts (into a …

Understanding Tlr3 Immune Response Activation In Cryptosporidium Parvum And Cryspovirus Pathogenesis, Surayya Hudayberganova

Biochemistry and Molecular Biology

Cryptosporidiosis is a serious gastrointestinal illness caused by a protozoan parasite known as Cryptosporidium. It is particularly dangerous for malnourished children and those with compromised immune systems. My research focuses on the Toll-like receptor 3 (TLR3) response to the Cryptosporidium parvum infection, specifically in the presence of the parasite’s viral mutualist named cryspovirus (CSpV1). Results using research methodologies like ELISA and RT-qPCR have indicated that TLR3 expression increases during the infection process of Cryptosporidium parvum (C. parvum). Furthermore, one intriguing observation concluded during this study suggests that administering the TLR3-specific inhibitor CU-CPT4a to infected cells drastically decreased this activation. This …

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 …

Understanding The Role Of Toxs As A Bile Sensing Component Of The Toxrs Virulence Regulatory System In Vibrio Spp., Minje Kim

Dartmouth College Ph.D Dissertations

Pathogenic Vibrio bacteria, such as V. cholerae and V. parahaemolyticus, colonize in the human small intestine to cause severe gastrointestinal disease. During the infection, these bacteria encounter bile salts, antimicrobial cholesterol metabolites secreted into the intestine. Pathogenic Vibrio species have evolved to utilize bile salts as signals to regulate virulence. The signaling depends in part on ToxRS, a conserved co-component transmembrane transcription regulator. ToxRS consists of the transcription factor ToxR and its membrane-tethered binding partner ToxS. ToxS is required for ToxR stability and full transcriptional activity. Although bile salts are known to influence ToxRS-dependent virulence gene expression, the molecular …

Analysis Of Bacterial Virulence And Resistance In A Model Of Recurrent Uti, Rachel L. Proper

Undergraduate Honors Theses

Urinary tract infection (UTI) is a major women’s health issue, affecting approximately 40% of women during their lifetime. Formation of a biofilm by UTI-causing bacteria poses a major challenge in treatment, as the protection provided by the biofilm hinders both host defenses and antibiotic treatment. Failure to eradicate these infections causes them to become recurrent (rUTI). Previous research indicates that rUTI may be comorbid with a mutation in the SERPINE1 gene, which causes fibrin to accumulate within the body. Literature also indicates that fibrin provides a better scaffold for bacterial attachment and, subsequently, biofilm formation. In this work it was …

Evaluating The Impact Of K135t Mutation On Malate Dehydrogenase Kinetic Activity, Emily Frost, Kaitlyn Mello

Undergraduate Research Symposium (2026- )

Malate Dehydrogenase (MDH) is a key protein in the citric acid cycle; its dysregulation can have catastrophic impacts, such as neurological and metabolic disorders, and various cancers. MDH catalyzes the reversible oxidation-reduction reaction between malate and oxaloacetate, also reducing NAD+ to NADH in the process. The citric acid cycle is one of the central metabolic pathways, connecting to other essential pathways, such as amino acid and fatty acid biosynthesis, highlighting the importance of understanding how MDH works. A key site in MDH is the flexible loop region (amino acids 119-137), responsible for substrate binding, catalysis, and orientation. The flexibility of …

Proline To Serine Mutation In Flexible Loop Region Of Malate Dehydrogenase, Anna Molstad, Hannah Robertson

Undergraduate Research Symposium (2026- )

Malate Dehydrogenase (MDH) is an essential enzyme that converts malate to oxaloacetate using the reduction of NAD+ to NADH. In humans, MDH plays a role in energy metabolism by catalyzing a key step of the citric acid cycle, important for energy production. Other indirect roles for MDH include gluconeogenesis and reoxidizing NADH from fatty-acid β-oxidation. An important feature of MDH is a flexible loop region that can alter substrate binding and enzyme activity, but its role is not well understood. Our study investigated how Pro123 to Ser (P123S) mutation in the flexible loop region affects MDH function. We hypothesized that …

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 …

Effect Of Novel Antimicrobial Compounds On Fungal And Bacterial Pathogens, Megan Wilderman

Honors Program: Senior Projects (Public)

Antimicrobial resistance is a growing concern in medicine¹ leading to a need for the development of novel compounds. Two compounds were tested in this study, 2-hydroxyethylhydrazine (HEH) and para-nitrophenyl-isocyanide (NPIC). HEH targets phosphatidylcholine (PC) production², and NPIC targets mitochondrial function³. Choline (Cho) is a compound that bypasses the inhibition of HEH through the Kennedy pathway.² Two-fold serial dilutions were conducted in 96-well plates to test the sensitivity of different bacteria to HEH and fungi to HEH and NPIC in different media types. A choline condition was also included in the HEH dilutions to test …

In Vitro And In Silico Analysis Of The Antibacterial Activity Of Bioactive Compounds Extracted From Pineapple Peel, Wafa Mohammad Sadik, Iman Tajer Abdullah, Lana Abed Alnajar

Makara Journal of Science

Antibiotic resistance is a critical global challenge that requires the discovery of alternative therapeutic agents. Plants -derived compounds, such as those found in Ananas comosus (pineapple)peel, offer promising antibacterial potential. This study aimed to evaluate the antibacterial activity of pineapple peel extract using both in vitro and in silico approaches. Ethanolic extracts of pineapple peel were fractionated using silica gel chromatography, and the resulting fractions were analyzed by GC-MS. Antibacterial activity was tested against Gram-positive and Gram-negative pathogens using the agar well diffusion method, and the inhibition zones were recorded. Molecular docking was performed to assess the interaction of identified …

Tlr3 Mediated Type I Interferon Response In Mammalian Cell Defense Against Cryptosporidium Parvum Infection., Anjelica Matias

Biochemistry and Molecular Biology

Cryptosporidium parvum is a major cause of a diarrheal disease which affects many children in the USA as well as the rest of the world, yet the contribution of its double stranded RNA (dsRNA) viral symbiont, Cryspovirus (CSpV1) to host innate immunity remains unclear. This study investigated whether CSpV1 activates Toll Like Receptor 3 (TLR3) signaling pathways and downstream Interferon type I (IFN I) responses in mammalian intestinal epithelial cells. Confluent Human Ileocecal Colorectal Adenocarcinoma cells (HCT8) were exposed to CSpV1, and the expression levels of Tumor Necrosis Factor Receptor-Associated Factor 3 (TRAF3), Nuclear Factor-𝜅-light chain enhancer of activated B-cells …

Oral Streptococcus And Vitamin B12 Deficiency In E-Cigarette Users: A Microbial–Nutrient–Neurotransmitter Axis Linking To Mood Disturbances, Maryam Sabah Naser, Ali Jabbar Abd Al-Hussain Alkawaz, Ali Abbas Hashim Almusawi, Ali Jalil Obaid, Hasanain Ayed Mohammed Al-Khafaji, Reihaneh Sabbaghzadeh

Karbala International Journal of Modern Science

Background: With the rising popularity of e-cigarettes, questions have emerged regarding their broader influence on oral ecology, nutrient absorption, and psychological health. Disruptions in the oral microbiome may alter vitamin B12 dynamics. This, in turn, may indirectly influence serotonin biosynthesis and mood regulation.

Methods: An observational cross-sectional study involved 150 young adults segregated into groups of 50 each as vapers, smokers, or non-users. Streptococcus sanguinis and vitamin B12 metabolism-related variable statuses methylmalonic acid and holotranscobalamin were quantified in samples, along with inflammatory markers interleukin-6, kynurenine/tryptophan ratio, and serotonin. Statistical techniques, including ANOVA and the Kruskal-Walli’s test, correlation, and serial mediation …

Characterizing The Human Metapneumovirus Matrix Protein And Its Role In Infection, Chase J. Heim

Theses and Dissertations--Molecular and Cellular Biochemistry

Human metapneumovirus (HMPV) causes severe respiratory tract infections in all cohorts, but especially in vulnerable groups such as children, older adults, and the immunocompromised. The matrix (M) protein of HMPV, like the M proteins of other members of the Mononegavirales order, is involved in virus assembly and budding. However, other functions of the HMPV M protein have yet to be elucidated. To investigate these various functions of the M protein, we used a peptide-conjugated phosphorodiamidate morpholino oligomer (PPMO) antisense agent designed to block translation of the M gene to reduce M expression during infection. Treatment with varying concentrations of an …

The Triangular Interaction Between Dietary Polyphenols, Gut Microbiota, And Metabolic Syndrome, Emily Bayliss

Senior Honors Theses

Type 2 diabetes mellitus (T2DM) is a growing global health concern characterized by peripheral insulin resistance as well as impaired insulin secretion from pancreatic β-cells. Emerging evidence suggests that the gut microbiome, specifically gut dysbiosis, an imbalance in the gut microbiome, is a critical modulator of the pathophysiology of T2DM. Dietary polyphenols, a diverse group of bioactive compounds that are abundant in plant-based foods, have recently gained attention for their potential to attenuate metabolic disorders through their antioxidant and anti-inflammatory properties as well as through modulating the composition and activity of gut microbes, thereby attenuating dysbiosis. However, the diabetic state …

Investigating The Impacts Of Azole Antifungals On Growth Of Cryptococcus Neoformans, Gnanambika Sindhe

All Theses

Cryptococcus neoformans, an opportunistic fungal pathogen is responsible for cryptococcosis, leading to approximately 181,000 deaths annually, predominantly in regions such as Sub-Saharan Africa. Fluconazole, a widely used fungistatic azole, is often administered due to its relative affordability and lower toxicity. However, resistance to fluconazole in C. neoformans can arise through aneuploidy, complicating treatment efforts. This study aims to deepen our understanding of resistance mechanisms to azole drugs by comparing fluconazole with other azoles, including both clinical and agricultural azole antifungals. Disk diffusion assays were performed to evaluate the ability of C. neoformans to develop resistance to these compounds, focusing …

Tracing The Journey Of Dissolved Organic Matter: From Leaf Litter Photodegradation To Microbial Processing In Tropical Streams, Samantha Nicole Sullivan

Chemistry & Biochemistry Theses & Dissertations

Dissolved organic matter (DOM) is a major reservoir of organic carbon in aquatic ecosystems and plays a central role in global carbon cycling through its transformation and remineralization to carbon dioxide (CO₂). As DOM moves from terrestrial environments into streams and rivers, its chemical composition is altered by a combination of microbial and photochemical oxidation processes that regulate both its reactivity and its persistence during transport. However, the molecular mechanisms governing these oxidative transitions, particularly in tropical ecosystems characterized by strong hydrologic seasonality and substantial inputs of plant-derived material, remain insufficiently resolved. This dissertation integrates ultrahigh-resolution mass spectrometry, optical characterization, …

Detection Method For Escherichia Coli Using Real-Time Polymerase Chain Reaction Targeting The Yhav Gene, Muktiningsih Nurjayadi, Anisa Fitriyanti, Royna Rahma Musie, Gusti Angieta Putri, Puan Aqila Azizah, Helzi Angelina, Grace Grace, Ananda Indah Putri Sihombing, Agus Setiawan, Jefferson Lynford Declan, Gladys Indira Putri, Dandy Akbar Juliansyah, Siti Fatimah, Ayu Berkahingrum, Irma Ratna Kartika, Fera Kurniadewi, Vira Saamia, Shyi-Tien Chen, Bassam Aboemolak, Hesham Ali El Enshasy

Makara Journal of Science

Escherichia coli is a foodborne pathogenic bacterium that can cause diarrhea, while yhaV is a virulence-associated gene linked to the toxin–antitoxin system in E. coli. This study was aimed at evaluating the confirmation, specificity, and sensitivity of a yhaV gene primer using real-time polymerase chain reaction. The yhaV-targeting PCR successfully amplified a DNA fragment with an amplicon length of 207 bp (base pairs) under an annealing temperature optimized to a range of 54 °C to 62 °C via gradient PCR. The PCR using the primer pair produced a consistent Ct (cycle threshold) of 14.14 ± 0.05 and showed …

Effect Of Histidine Tag On The Enzymatic Activity Of Pseudolysin And Its Interaction With The Streptomyces Metalloprotease Inhibitor (Smpi) Protein, Adewale Adeboye Adewole

Electronic Theses and Dissertations

Pseudolysin (PLN) protein is a major virulent factor in Pseudomonas aeruginosa infection. PLN belongs to the family of zinc-dependent metalloproteases. It is naturally inhibited by a smaller protein called streptomyces metalloprotease inhibitor (SMPI), secreted by Streptomyces nigrescens. Previous and current studies demonstrate that the interaction between PLN and SMPI offers unique mechanistic insights for drug development against infections caused by P. aeruginosa. This study investigated the effect of N-terminal Histidine (His) tag on the enzymatic activity of PLN and its interaction with SMPI. His-tagged PLN and SMPI proteins were expressed in bacteria and purified by affinity chromatography …

Evaluation Of Nature-Based Engineering Stream Restoration Of Plaster Creek Through Leisure Creek Condominium Association, Julie Wildschut, Rebecca Evenhouse, Andrea Lubberts, Dave Warners, Haley Weesies

Faculty and Professional Research

When land that was once covered with vegetation and soil becomes dominated by impervious concrete and rooftops, the amount of water infiltrated by the ground plumets. As a result, most suburban areas contribute to the impairment of streams by adding excess water, nutrients, and pollutants to nearby waterways each time it rains. One harmful result of this is the erosion of stream banks. The rapid influx of water that occurs after rain events can destabilize and erode stream banks, resulting in excess sediment in the water. One location where this happened very prominently was a section of Plaster Creek which …

Characterization Of Sars-Cov-2 Replication And Transcription Complexes Via Structural And Evolutionary Approaches, Amelie Ghirardo, Ben Shabatian, Avishai Aghelian, Kyle Tau, Eleonora Gianti

Undergraduate Research

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused around 700M cases and over 7M COVID-19-related deaths recorded worldwide (World Health Organization, March 2025). Aiming to effectively combat this and other disease-causing Coronaviruses (CoV), unprecedented research efforts led to the development of new vaccines and antiviral therapies. Due to emergence of variants of concern (VOCs) with increased transmissibility, immune evasion from vaccination, and potential to resist the available treatments, SARS-CoV-2 continues to represent a major threat to global health. Hence, there is a pressing need to discover new antivirals with broad-spectrum efficacy against multiple SARS-CoV-2 variants and related CoVs. This project …

Novel Chloroviruses With Unique Glycans On Their Major Capsid Proteins, Cayden J. Homolka

Honors Program: Senior Projects (Public)

Chloroviruses, of the family Phycodnaviridae, are large, dsDNA viruses with a genome of 290 to 410 kb. These virus genomes are so large that they are classified as “giant viruses”. Within this genome, up to 16 tRNAs and 330 to 450 proteins are encoded. Among the massive amounts of genes and proteins are unique carbohydrate synthesis/metabolism genes, which are responsible for the glycosylation of chloroviruses major capsid proteins. In most viruses, these proteins are glycosylated by the host enzymes located in the endoplasmic reticulum. Instead, Chloroviruses encode their own glycosylation machinery; essentially decorating themselves. Furthermore, these chlorovirus glycans are unlike …

Expanding Inducible Epithelial Resistance Against Pneumonia: Novel Virus, Novel Receptor, Michael Longmire

Dissertations and Theses (Open Access)

Pneumonia is the leading infectious cause of death worldwide and presents a continuing risk among immunocompromised patients. Our work has been focused for many years on the phenomenon of inducible epithelial resistance, where activation of the innate immune response in the airway epithelium is necessary and sufficient to produce a pathogen-killing but self-protective environment to prevent severe disease. Inducible resistance is pathogen-agnostic and has been demonstrated against an array of respiratory infections. We achieve this using a combination of pattern recognition receptor agonists – Pam2CSK4 and ODN M362 being the current formulation – which produce synergistic levels of pathogen reduction …

Metabolite Analysis To Understand Factors Limiting Microbial Fermentation At High Substrate Concentrations, Bishal D. Sharma

Dartmouth College Ph.D Dissertations

Clostridium thermocellum, a thermophilic anaerobic bacterium, holds promise as a biocatalyst for conversion of lignocellulosic biomass into biofuels. This microbe has been subjected to various metabolic engineering strategies, including the deletion of genes encoding secondary fermentation products such as H₂, formate, acetate, and lactate, as well as the expression of heterologous genes to redirect carbon flux toward ethanol production. Despite these efforts, achieving economically viable ethanol titers remains a challenge. We hypothesized that studying how intracellular metabolite concentrations change as fermentation stops could reveal metabolic bottlenecks or regulatory mechanisms limiting ethanol production at high titers. However, metabolomics studies at …

Biochemical And Structural Insights Into The Yersinia Effector Yopm And Its Negative Regulation Of The Pyrin Inflammasome, Bethany Wairimu Mwaura

Dartmouth College Ph.D Dissertations

Bacteria utilize sophisticated secretion systems to inject effectors into host cells in order to facilitate their survival and replication in the host. Some pathogenic species of Gram-negative bacteria use a conserved contact-dependent T3SS to inject a wide array of effectors. While the effectors diverge in their structures, functions and cell-localization, the T3SS is well conserved. Several effectors discussed in this thesis target key host inflammasome responses. The focus of this work is how the Yersinia effector YopM inhibits the pyrin inflammasome. During Yersinia infection, two effectors, YopE and YopT inadvertently activate the pyrin inflammasome while targeting RhoA to avoid phagocytosis. …

Induced Mutagenesis In West Nile Virus Non-Structural Protein 3 With A Discussion Of The Mutation's Effects On Viral Properties, Caden Connealy

Honors Program: Senior Projects (Public)

West Nile Virus (WNV), a member of the Flaviviridae family and introduced to the Western hemisphere in 1999, presents a unique and emerging threat to human health. Infection in humans is often mild but can occasionally result in severe neurological impairment and even death. West Nile Virus non-structural protein 3 (NS3) plays an important role in the process of viral genome amplification. More specifically, the C-terminal domain of the protein folds into a helicase enzyme, which is responsible for the “unwinding” of double-stranded RNA intermediates and RNA secondary structure on the WNV genome. This is a vitally important step in …

Transcription Factor Binding And Discovery Of Novel Gene In The Opportunistic Human Pathogen, Pseudomonas Aeruginosa, Alaina Westee

Symposium of Student Scholars

Pseudomonas aeruginosa (PA) is a gram-negative, ubiquitously-found bacterium that primarily causes nosocomial, or hospital-borne, infections within immunocompromised patients. Therefore, it has been deemed a critical priority pathogen by the World Health Organization (WHO) and the Center for Disease Control (CDC), generating a need for research on its fundamental biology. The Van Dyke laboratory focuses on proteins called transcription factors, which promote or repress gene expression to regulate an organism’s functioning. We are specifically studying the cadmium-responsive transcription factor, CadR, due to the importance of metals in virulence and the lack of information on PA’s response to metal fluctuations. We intend …

Microbial And Plant Biodiversity In Appalachian Agroecosystems And Their Implications For Soil Health, Kinsey Reed Close

Graduate Theses, Dissertations, and Problem Reports (ETD)

The sustainability of agricultural landscapes depends on understanding the complex interactions between plants, soil, and microbes. In Appalachia, a region shaped by complex terrain and long histories of human and ecological interaction, small family farms produce hay, livestock, and row crops. These agroecosystems, though often treated as “artificial” by many ecologists, have the potential to support both food production and biodiversity conservation if managed with an understanding of ecological complexity. This dissertation examines how plant and microbial diversity interact with soil and management to influence nutrient cycling, soil health, and long-term resilience in Appalachian agricultural systems. A literature review revealed …

Reversible Degradation Of Peptidoglycan By Lytic Transglycosylases, Aaron Devereaux

Theses and Dissertations (Comprehensive)

Antimicrobial resistance continues to be a burden on the global healthcare system with an estimated cost of billions of dollars and millions of deaths each year. Recently, there has been little to no development on new antibiotics to treat bacterial infection, and any that are developed become resisted to within a few years. Both Gram-positive and Gram-negative bacteria contain a mesh-like layer called peptidoglycan (PG) that surrounds their cells providing strength, cell shape, and protection from their environments. This layer is a polymer of N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) connected via a b-1,4-glycosidic bond, with each strand being cross-linked …