Microbiology Commons^™

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 …

Characterizing The Microbial Structure And Function In Black Soldier Fly Digested Dairy Manure And Subsequent Larvae, Branden N. Pierce

Theses and Dissertations

This work examined the microbial structure and gene expression found in Black Soldier Fly larval guts and their frass when reared on dairy cattle manure that had been amended with either R. rhodococcus 21198, P. polymyxa 8158, or both and compare the results to larvae reared on untreated manure. First an overview of literature surrounding projected global food supplies and the possible use of insects to either increase them or mitigate the environmental effect of producing said supply. A cellulose degradation assay was performed to assist in determining which bacterial species to use as amendments. Characterization of the microbial communities …

Genetic Screen For Regulators Of Pol4, A Dna Repair Polymerase In Saccharomyces Cerevisiae, Pasang Dolma Sherpa

Theses and Dissertations

In Saccharomyces cerevisiae, DNA polymerase 4 (POL4) is the beta repair polymerase, the product of the POL4 gene, and is involved in base excision repair (BER) and microhomology-mediated end joining (MMEJ). Despite its involvement in these repair pathways and its conservation across eukaryotes, deletion of POL4 shows no detectable phenotype under standard laboratory conditions. I hypothesized that unknown genes act as backup systems, providing redundant activities that allow pol4Δ cells to survive. To test this, a genetic screen for mutants showing synthetic lethality with pol4Δ was implemented. I constructed a strain lacking the POL4 gene and carrying …

Degradation And Metabolic Analysis Of Synthesized Quorum-Sensing Signals By The Model Eukaryote Chlamydomonas Reinhardtii, Adam Josef Bach

Theses and Dissertations

Bacterial organisms can “talk” with one another on a colony-wide scale using a communication system known as quorum-sensing (QS) via chemical signals. These signals are produced at a basal rate throughout the life of the bacteria and are classified as autoinducers, which diffuse across the cell membrane. Once the critical concentration is reached, they begin to diffuse back into the cell and initiate a phenotypic change. As these signals exist outside the membrane of their producer, they are also accessible to other organisms. It has already been noted that some plant species uptake these compounds through their roots and break …

Metagenomic Profiling Of Gut Microbiome Signatures Across Liver Disease Stages And Hcv-Related Hepatocellular Carcinoma In Egyptian Patients, Marwa A. Zahra

Theses and Dissertations

Dysbiosis in the gut microbiome, particularly concerning the synchronous crosstalk between the gut and the liver, has been associated with various diseases. This study profiles the gut microbiome in liver diseases among Egyptian patients, with a focus on the hepatitis C virus (HCV) and hepatocellular carcinoma (HCC), both of which are highly prevalent in Egypt. Utilizing shotgun metagenomic sequencing, we analyzed microbial gene catalogs and taxonomic profiles from 46 Egyptian patients categorized into five groups: healthy individuals, liver disease patients of different etiologies, post-HCV, treated HCV, and HCV-HCC patients. Healthy and treated HCV patients exhibited distinct microbial profiles characterized by …

Environmental Monitoring In Shallow Lakes: Public Health Threats In Urban Waters, Kyleigh E. Johnson

Theses and Dissertations

Lakes are an integral part of urban and suburban communities, providing ecological, recreational, and public health benefits. Many of these lakes are located in densely populated areas and are subject to urban influences on water quality. Algal toxins and Escherichia coli are two common recreational concerns. Algal toxins come from harmful algal blooms that are influenced by nutrient availability and temperature, while bacteria are often introduced through run-off and animal waste. Sampling every 3-4 weeks from May-October 2025 allowed for the assessment of seasonal patterns and site-specific differences across nine lakes in the Richmond area. The highest bacterial concentrations appeared …

Exploring The Diversity And Biology Of Unique Giant Broad Host Range Bacteriophages In Natural Environments, Tannaz Mohammadi

Theses and Dissertations

Microbial interactions within the rhizosphere play a crucial role in shaping bacterial community diversity and function. To explore these dynamics, we isolated 21 bacterial strains from soil and plant root samples collected near Rocky Branch Creek on the University of South Carolina campus. Our findings revealed that a significant proportion of these bacteria are lysogenic for CbK-like phages belonging to the Dolichocephalovirinae subfamily. Additionally, we isolated free bacteriophages directly from the same soil samples and found them to be closely related to those harbored within lysogenic bacteria. Surprisingly, despite predictions of a narrow host range, most of these phages, both …

Analyzing The Role Of A Dual-Function Diguanylate Cyclase / Phosphodiesterase For Attachment And Motility In Agrobacterium Tumefaciens, Priya Aryal

Theses and Dissertations

Cyclic diguanylate monophosphate (c-di-GMP) is a second messenger that is responsible for attachment and motility in many prokaryotic systems and controls the signaling pathway for the motile to sessile transition in many bacteria. Many c-di-GMP-metabolizing proteins are diguanylate cyclases (DGCs), responsible for the synthesis of c-di-GMP and characterized by a c-di-GMP synthesizing domain, e.g., GGDEF domain. Other c-di-GMP-metabolizing proteins contain c-di-GMP degradative domains, e.g., EAL, characterized by phosphodiesterase activity (PDE). In Agrobacterium tumefaciens, out of 31 predicted proteins regulating the c-di-GMP level, this project focuses on the predicted dual-function DGC/PDE, DcpB. We hypothesized that DcpB plays a role in the …

Biogenic Calcite Precipitation For Coastal Sand Stabilization: A Synergistic Approach Using Marine Bacteria And Natural Fibers, Aparna Gs

Theses and Dissertations

Coastal erosion, driven by natural forces such as waves, tides, winds, and currents and further intensified by anthropogenic activities like urbanization, climate change, and coastal infrastructure development, poses a significant threat to shoreline stability. Conventional erosion control methods, including jetties, embankments, and artificial reefs, often face limitations in sustainability and effectiveness. In this context, microbially induced calcite precipitation (MICP) has emerged as a promising ecofriendly solution for ground stabilization.

The present study investigates the potential of an indigenous ureolytic marine bacterium, Bacillus sp. N₉, isolated from the coastal sediments of Nagapattinam, Tamil Nadu, for coastal sand stabilization. The strain was …

The Role Of Biofilm Matrix On The Growth, Survival, And Diagnosis In Enterobacteriaceae, Kavi Bharathi R

Theses and Dissertations

Bacteria in nature live together encased in a matrix creating community ecosystems called biofilms, this structured space protects them from hostile environments. This study aimed to understand the role of the biofilm matrix in the growth and survival of Enterobacteriaceae. Our hypothesis proposes that subgroups of individuals within a biofilm can specialize in the production of different matrix components.

Matrix expression is metabolically costly, despite its unicellular simplicity, microbes can coordinate complex behaviour like sharing of matrix between producers and non-producers as an adept evolutionary strategy. Their resilience to stress during biofilm formation was studied to assess their abilities to …

Propelling Whole-Cell Biosensor Creation By Leveraging Gene Fusion To Assemble Synthetic Functional Transcription Factors For The Detection Of Biomarkers, Samuel J. Verzino

Theses and Dissertations

Biosensors are analytical devices that leverage biological modules for the detection of molecules of interest. As customizable tools designed to aid in a wide array of diagnostics, these instruments are rapidly advancing the field of synthetic biology. While varied in their construction and purpose, biosensors are ultimately concerned with converting a physicochemical stimulus into a detectable signal. Among the many existing variants, whole-cell biosensors (WCBs) stand out due to their versatility and engineering potential. WCBs are a type of biosensor in which a physiologically active cell sustains an array of biomolecular elements - receptors, transporters, regulators, etc. - capable of …

Functional Analysis Of Ligand Binding Domain 2 Of Outer Surface Protein C Of Borreliella Burgdorferi, Gavin Z. Chambers

Theses and Dissertations

Lyme disease, caused by the spirochete Borreliella burgdorferi, is the most common vector-borne infection in North America. A critical determinant of early mammalian infection is outer surface protein C (OspC), a highly variable lipoprotein that is indispensable for spirochete survival but whose precise function remains unresolved. OspC has been proposed to mediate diverse roles, including complement evasion, adhesion, tissue dissemination, and antiphagocytic activity, supporting the view that it is a multifunctional virulence factor. Structural studies have identified two putative ligand-binding domains (LBD1 and LBD2), with LBD2 forming a solvent-exposed crown at the membrane-distal end of the OspC dimer.

To …

A Novel Silver-Ruthenium-Based Antimicrobial Kills Gram-Negative Bacteria Through Oxidative Stress-Induced Macromolecular Damage, Patrick O. Tawiah

Theses and Dissertations

The rise in drug-resistant bacteria, together with the decline in antibiotic development, requires new strategies for infectious disease control. Gram-negative pathogens are particularly challenging to combat due to their outer membrane. This study highlights the effectiveness of the silver-containing antimicrobial AGXX® against the Gram-negative bacterium Escherichia coli. AGXX® is a promising silver coating that presumably kills bacteria through the generation of reactive oxygen species (ROS). However, neither AGXX®’s mode of action is fully understood, nor have its effects on Gram-negative bacteria or bacterial response and defense mechanisms towards AGXX® been studied in detail. Here, I report that the bactericidal …

Exploring The Role Of Host Immune Responses And Bacterial Sensory Pathways In The Development Of Treponema Denticola-Mediated Periodontal Disease, Annie N. Hinson

Theses and Dissertations

Periodontitis is a chronic inflammatory disease driven by dysbiotic microbial communities and maladaptive host responses. Treponema denticola, a spirochete pathobiont, is strongly associated with disease severity. However, the molecular mechanisms underlying its interaction with host tissues and regulation of virulence remain incompletely understood. This work examines both the epithelial immune responses and bacterial transduction systems that shape T. denticola pathogenesis. Transcriptomic analysis of gingival keratinocytes revealed IL-36γ as the most highly induced cytokine following infection with T. denticola. Functional studies demonstrated that IL-36γ induction occurs in a dose- and time-dependent manner through TLR2/6 signaling, requiring the NF-κB, PI3K/Akt, and …

Molecular Mechanisms Of Kynurenine-Mediated Lifespan Regulation In Yeast, Ryan E. Counterman Jobb

Theses and Dissertations

The kynurenine pathway is a highly conserved pathway that acts as the primary pathway for tryptophan catabolism and has been found to be involved in lifespan regulation across many diverse organisms. Caloric restriction (CR) is the only known dietary intervention to date that both increases the mean lifespan and the health span of multiple organisms, although the molecular mechanisms of these effects are not fully understood. There are known and sometimes contradictory relationships between the kynurenine pathway activity and the life- extending effect of CR but the crosstalk between the two is not well characterized. Understanding these relationships could lead …

Horizontal Gene Transfer In Intergenomic Conflicts Between Bacteria And Their Genetic Parasites, Pavithra A.S

Theses and Dissertations

Bacteria are constantly infected by obligate acellular genetic parasites, such as plasmids and phages. The genetic conflicts between bacteria and their parasites, aggravated by horizontal gene transfer, exert significant ecological and evolutionary pressure on their respective genomes. The eco-evolutionary significance of parasite-derived elements on bacterial genomes is not well understood.

This study explored the genomics of plasmid-derived genetic elements such as antimicrobial resistance genes (ARGs), type II endonuclease toxin-antitoxin systems (TAs) and endonuclease colicin-like bacteriocin (CLB) operons, and phage-derived prophages of Escherichia coli using bioinformatics and developing novel hybrid agent-based models. We sequenced eight E. coli isolated from local wastewater …

Characterizing The Quorum Sensing (Qs) System In The Model Eukaryote Chlamydomonas Reinhardtii, Kirstin Donnette Cutshaw

Theses and Dissertations

Group behaviors in microorganisms are often regulated by low-molecular weight molecules that enable them to sense population density, a signaling system known as quorum sensing (QS). QS in prokaryotes has provided insight into the role ‘social’ behaviors play in the bacterial world and refined our models of virulence, bacterial motility, and more. While less common, similar behaviors are observed in certain fungi, primarily yeasts, in which QS controls cell morphology, biofilm production, and other phenotypes. We have recently pursued the potential for QS to be more broadly distributed among unicellular eukaryotes, which could significantly alter our understanding of social behaviors …

Pipecolic Acid And Novel Insights Into Cerebral Malaria, Akua E. Mensah

Theses and Dissertations

Cerebral malaria (CM), a severe manifestation of Plasmodium infection, prompts our investigation into the nuanced role of pipecolic acid in its pathophysiology. To unravel the molecular intricacies, we conducted in vitro lysine labeling techniques of mice infected with P. berghei ANKA parasites, and human P. falciparum grown in vitro, aiming to discern the impact of Plasmodium on pipecolic acid production. Previous observations indicated an elevation in pipecolic acid levels correlating with neurological decline in children with CM. In our study, confirming elevated pipecolic acid presence in the plasma and brain tissues of CM patients and the animal model of CM, …

Preventing Orthopedic Implant Associated Biofilm Infections Using Transition Metal Complex Laminated Bioactive Implants, Sowndarya J

Theses and Dissertations

Orthopedic implants are medical devices employed to repair the damaged structure and function of an injured musculoskeletal system. It helps millions of people suffering from bone fractures and arthroplasty. The increased use of orthopedic implants has given rise to implant-associated biofilm infections. Biofilm-mediated Implant-associated osteomyelitis (IAO) is a major concern in the medical field, wherein the treatment involves debridement, administration of antibiotics and removal of implants leading to increased cost of treatment.

The keystone bacterial pathogens involved in orthopedic implant-associated infections are Staphylococcus aureus and Acinetobacter baumannii which are members of the ESKAPE pathogens. A. baumannii has gained resistance against …

Antibacterial And Anticancer Activities Of A Fosmid Clone From Atlantis Ii Red Sea Brine Pool., Marina Nabil

Theses and Dissertations

Antimicrobial resistance (AMR) and cancer are among the top global human health issues requiring urgent control practices. AMR caused 5 million death cases around the world in 2019. This number is expected to reach 10 million deaths by 2050. Cancer deaths reached 10 million in 2020. Additionally, anticancer drug resistance is a common cause of death among cancer patients. Screening for novel compounds is one of the strategies recommended by the World Health Organization (WHO) to control drug resistance in microbial and cancer cells. Marine natural products (MNPs) are characterized by chemically diverse structures with various bioactivities, especially in extreme …

Phosphomolybdic Acid-Doped Zeolitic Imidazolate Framework-8 Hybrid: Nanostructured Material With Synergistic Antibacterial Effect, Mariam Mohammad Abdelkhalek

Theses and Dissertations

Bacterial infections represent a major global health concern, causing millions of deaths and significant economic burdens. The development of nanostructured surfaces with antibacterial activity can revolutionize infection control practices. In this study, a hybrid material of Zeolitic imidazolate framework-8 (ZIF-8) doped with phosphomolybdic acid (PMA) was synthesized and characterized by FESEM, EDS, XRD, FTIR, and N2 sorption isotherm. The antibacterial activity against Escherichia coli as a model organism was tested by colony forming unit (CFU) reduction assay, minimum inhibitory concentration (MIC), and time-kill curve. PMA@ZIF-8 performance as an antibacterial agent was superior to its individual constituents, suggesting synergistic effect of …

Persistence Of Wastewater-Associated Antibiotic Resistant Bacteria In River Microcosms, Aoife P. Mahaney

Theses and Dissertations

The spread of antibiotic-resistant bacteria (ARB) associated with wastewater is a significant environmental concern, but little is known about the persistence and proliferation of these organisms in receiving water bodies after discharge. To address this knowledge gap, we performed a series of microcosm experiments in which river water was amended with either untreated or treated wastewater, and the abundance of viable ciprofloxacin-, Bactrim-, and erythromycin-resistant bacteria was monitored for 72 hours.

Both types of wastewater amendments increased the initial abundance of ARB compared to microcosms containing only river water. The increase was greatest with untreated wastewater, but that effect decreased …

Investigating The Protein Interactome Of Escherichia Coli To Understand Metabolic Regulation When Proteins Bind: A Systems Biology Study., Shomeek Chowdhury

Theses and Dissertations

Proteins bind other proteins and work together as machines to perform many biological functions. Metabolic enzymes governing the life-sustaining metabolic reactions and therefore, metabolism are proteins which also binds other proteins. In this dissertation work, I have explored proteins when they interact with metabolic enzymes, play any role in regulating the cell’s metabolism. I study this phenomenon in Escherichia coli whose protein-protein interaction data is readily available in public databases with proper reference to the experimental study. Another good reason is the predictions we make in this computational study can be tested and validated in E. coli as it is …

Increased Coding Potential Of Bovine Herpesvirus 1, Victoria Jefferson

Theses and Dissertations

Bovine respiratory disease (BRD) costs the cattle industry millions of dollars in costs in treatment and loss every year in the United States. A significant pathogen often contributes to BRD is Bovine Herpesvirus 1 (BoHV-1), a double stranded DNA virus with the ability to establish latency in the trigeminal ganglia and neurons. Primary infection with BoHV-1 results in immunosuppression that increases the risk of secondary bacterial infection and pneumonia. Because herpesviruses infect their hosts for life and can be reactivated in times of stress, BoHV-1 can present a recurring risk of BRD. The following research aims to expand the knowledge …

Evaluating The Role Of The Bovine Vaginal Microbiome In Neonatal And Maternal Health Outcomes, Riley D. Messman

Theses and Dissertations

The dam vaginal microbiota is the first major microbial inoculating community within the neonate. The composition of the dam vaginal microbiota has implications in calf commensal microbiota development. Alterations of the dam microbial community prior to parturition could alter inoculating communities and immune responses in both the dam and calf. Thus, authors aimed to elucidate the microbial community composition of the bovine dam vaginal and calf nasal microbiota post-partum after utilizing betadine lavages (BL). The dam vaginal and calf nasal microbial communities and immune responses were evaluated at 0-, 15-, 30- and 60-day post-partum. Microbiota composition of the dam haircoat, …

Evaluating The Immunogenicity Of Colonization Proteins Of S. Pneumoniae For Identification Of Vaccine Candidates, Isidora Fereday

Theses and Dissertations

Streptococcus pneumoniae is typically an asymptomatic colonizer of the upper respiratory tract but can cause invasive disease in susceptible populations. Pneumococcal vaccines which are currently in use have failed to significantly reduce colonization by S. pneumoniae. To control invasive pneumococcal disease, novel strategies must be utilized. One such strategy is to reduce or eradicate colonization by pneumococcus. Supplementary vaccination with pneumococcal proteins important for colonization could serve to prime the immune system against these targets. This study serves as an initial step towards identification of crucial pneumococcal colonization proteins which may previously have been uncharacterized. Assessing the immune reactivity …

Nutritional Strategies To Reduce Salmonella Enteritidis Infections In Laying Hens: Prebiotic, Probiotic, And Precision Biotics, Ishab Poudel

Theses and Dissertations

Salmonella Enteritidis (SE) infections in laying hens is a significant cause of foodborne illness linked to the consumption of contaminated eggs. This dissertation encompasses novel strategies aimed to explore appropriate in-vitro and in-vivo models to evaluate the effects of these novel strategies to reduce SE in laying hens. Firstly, we investigated the potential probiotics, prebiotics, and essential oil combinations to reduce SE in-vitro. The results showed that probiotics and prebiotics are equally effective to reduce SE. In subsequent studies, we evaluated the role of vaccination history on cecal microbiota and SE infections with various doses of oral SE challenge. …

Use Of Comparative Genomics And In Vitro Screening Approach To Identify Vaccine Candidates For The Food-Borne Pathogen Campylobacter Jejuni, Sabin Poudel

Theses and Dissertations

Campylobacteriosis is a leading foodborne illness worldwide, primarily caused by Campylobacter jejuni (C. jejuni) which is associated with poultry consumption. The emergence of antibiotic resistance has emphasized the need for alternative strategies to control C. jejuni colonization in poultry. To assess the prevalence of C. jejuni in poultry, 270 cloacal swab samples were collected from broilers raised under No-Antibiotics Ever system. Among these samples, 16.3% were identified as C. jejuni positive. Notably, these isolates exhibited a diverse range of virulence factors and antimicrobial resistance genes, with 61.36% of isolates showing hyper-motile and 20.45% demonstrating multidrug resistance. Following isolation, whole genome …

Evaluation Of The Virulence Potential Of Avian Pathogenic Escherichia Coli Isolated From Broiler Breeders With Colibacillosis In Mississippi, Jiddu Joseph

Theses and Dissertations

Avian pathogenic Escherichia coli (APEC) is a bacterium that is responsible for colibacillosis in birds. However, information about broiler breeder APEC isolates is limited, but the data is critical due to the transfer of this bacteria down the production pyramid to progenies resulting in high mortality. Therefore, we evaluated the phenotypic virulence characteristics of 28 isolates using embryo lethality and day-old chick challenge assays. Also, the in vitro adhesion and invasion potential of selected nine isolates were identified. Results showed more than 1/3^rd of the isolates were highly virulent and the virulence increased as the number of virulence-associated genes …

Investigating Potential Indicators Of Soil Health Through Microbiome Response To Environmental And Anthropogenic Stressors, Austin Cook

Theses and Dissertations

Traditionally, the analysis of soil health has overlooked the biological component of soil due to poor understanding of connections between the microbiome and empirically measured soil health indicators. The purpose of this study was to assess the effects of environmental and anthropogenic stressors on the soil microbiome, with the aim of identifying measurable soil biological indicators. Chosen soils were examined under distinct conditions to evaluate the effect of selected environmental and anthropogenic stressors on the microbiome. Soil biological responses were analyzed via enzymatic response, microbial functional genes, and microbial community. Environmental factors such as soil moisture and organic matter showed …