Microbiology Commons^™

Indigenous Toxin Affects Cell Viability, While An Artificial Proteolytic Queueing Causes The Upregulation Of Specific Genes, Mohammed Salahuddin

Electronic Theses and Dissertations

Studying bacterial physiology is crucial to understand the fundamental mechanisms that govern bacterial growth, survival, and adaptation. This thesis combines two chapters investigating bacterial physiology by studying important cellular processes like bacterial toxin-antitoxin systems and proteolytic pathways. The first chapter involves studying bacterial toxin-antitoxin systems to understand the regulation and function of hypothetical toxin-antitoxin (TA) systems of bacteria and the effects of these TA systems on bacterial growth and survival. The emergence of these genetic modules in bacterial research and the unrevealing of some of their important roles in cell physiology in recent years has drawn much attention in scientific …

Control Of Persistent Environmental Listeria Monocytogenes Using Phenotypic And Genomic Approaches, Bhaswati Chowdhury

Electronic Theses and Dissertations

No abstract provided.

Laboratory Practices And Antimicrobial Resistance In A Florida Hospital, Crispina Marie Sy-Trias

Walden Dissertations and Doctoral Studies

Antibiotic resistance is a health threat affecting millions of Americans. Microorganisms develop resistance to antibiotics, rendering them useless for treating infections. The purpose of this quantitative study was to assess the associations between sample processing time and antibiotic resistance and is based on the health belief model. A retrospective specimen tracking activity of data from November 2019 to November 2020 was obtained by random sampling of 246 bacterial cultures. One hundred ninety-six (80%) samples were processed on time, and 50 (20%) were delayed; 167 (68%) samples were determined to have the presence of antimicrobial resistance (AMR), and 79 (32%) with …

Bioprospecting For And The Applications Of Halophilic Acidophiles In Bioleaching Operations, Melissa K. Corbett, Elizabeth L. J. Watkin

Research outputs 2022 to 2026

The economic recovery of metals from sulfide ores has become a topic of increasing interest due to the escalating demand for critical minerals and the reducing grade of available ores. Bioleaching is the use of acidophilic iron and sulfur-oxidising microorganisms to facilitate the extraction of base metals from primary sulfide ores and tailings. One significant issue limiting the use of bioleaching is the availability of freshwater due to the sensitivity of these microbes to chloride. The use of saline tolerant acidophilic iron- and-sulfur oxidising microorganisms will go a long way to addressing this issue. There are three possible means of …

Effects Of Altering Physiologically Relevant Cholesterol Levels And Media Types On Porin Gene Expression In Klebsiella Pneumoniae And The Resulting Impact On Antibiotic Resistance, Megan R. Camden

UNF Graduate Theses and Dissertations

Klebsiella pneumoniae is a Gram-negative, non-motile bacterium belonging to the Enterobacteriaceae family. K. pneumoniae is a rising threat in the clinical setting, as there has been a large increase in the presence of antibiotic resistant isolates. While much research is conducted on laboratory and clinical strains of bacteria, not much is known regarding the impact that human physiology can have on bacterial gene expression, and in response, to antibiotic susceptibility. The goal of this study is to determine if physiologically relevant cholesterol levels and media types impact porin gene expression and antibiotic resistance in K. pneumoniae. To accomplish this, …

Confocal Analysis Of Sindbis Virus In Aedes Aegypti Unveils Novel Infection Site At Pyloric Armature, Katie Gillian Peters

UNF Graduate Theses and Dissertations

Arthropod-borne viruses (arboviruses), such as Sindbis virus (SINV), generate foci of infection within the midgut of viremic blood-fed mosquitoes. Arboviruses can disseminate out of the midgut into the surrounding musculature and hemolymph, eventually making it to the salivary glands where virus can be transmitted by saliva during a subsequent blood-feed. In this study, the virus SINV containing the reporter gene GFP, combined with immunohistochemistry, was imaged using confocal microscopy and used to evaluate the infection within the vector mosquito Aedes aegypti. The spatial distribution of SINV infection revealed two common characteristics of foci generated in the midgut. (1) There …

Microbial Communities In The Guana Tolomato Matanzas National Estuarine Research Reserve: An Assessment Of The Responses Of Spartina Alterniflora Epiphytes To Nitrogen Enrichment, And A Characterization Of Benthic Cyanobacterial Diversity, Anne C. Hurley

UNF Graduate Theses and Dissertations

Elevated nitrogen and phosphorus inputs from anthropogenic sources, which can lead to significant increases in algal biomass and changes in algal community composition, poses a serious threat to estuarine ecosystems worldwide. While numerous studies have addressed the impacts of nutrient enrichment on epiphytic algae in seagrass habitats, few have investigated potential nutrient-driven changes to epiphytes on emergent salt marsh plants, such as Spartina alterniflora. Epiphytic microalgae on S. alterniflora play an important role in food availability in salt marsh ecosystems, and epiphytic nitrogen-fixing cyanobacteria also provide an important source of nitrogen for salt marsh consumers. The first study included …

Exploring The Microbial Composition Of Moonmilk In Wind Cave National Park, Emma Pellegrino

Honors Program Theses

Moonmilk is a white substance mainly composed of calcium carbonate (CaCO3) that is often found in limestone caves. It is one of many mineral composites, or speleothems, in Wind Cave National Park South Dakota and is thought to be formed by microbial activity. This cave system is a complex, isolated environment that serves as an analog for similar domains beyond the Earth. Each site has varying degrees of human exposure, from public tour routes to caverns only occasionally visited by park rangers, making it an ideal place of study for pristine samples in extreme conditions. Wind Cave also varies in …

Monitoring Archaeal Persistence In Cultivation, Payton Hall

Honors Program Theses

It was previously thought that microbes in the domain Archaea were only found in extreme environments such as hot thermal vents at the bottom of the ocean and hypersaline environments, but as scientists began to use environmental DNA to survey soil, they detected archaea from the phylum Thaumarchaeota in relatively benign environments including farm fields, forests, and prairies. In spite of their widespread global distribution, relatively few of these species have been grown in laboratory culture. It is now known that Thaumarchaeota play an important role in the nitrogen cycle because they can generate energy through ammonia-oxidation. To increase the …

Evaluation Of Methods To Analyze Microbial Composition In Soils, Joseph Correa

Honors Program Theses

DNA testing has become a vital tool for studying microbes in their natural environments, but there is a lack of standardization in the protocols for extracting environmental DNA. Cave systems provide a special and unique area to research how life thrives in extreme environments. Many parts of caves receive no sunlight and very little nutrients yet harbor microbial communities. Previous work in our lab developed a DNA extraction protocol that works with a wide range of microbial species and with different soil types. I updated this protocol by adding a pre-lysis rinse step and tested whether it performed better with …

Elucidating The Role Of A Staphylococcal Glucosaminidase In Host Innate Immune Responses, Zachary Resko

Dissertations

The peptidoglycan of Staphylococcus aureus is a critical cell envelope constituent and virulence factor that subverts host immune defenses and provides protection against environmental stressors. Peptidoglycan chains of the S. aureus cell wall are processed to characteristically short lengths by the glucosaminidase, SagB. It is well established that peptidoglycan is an important pathogen-associated molecular pattern (PAMP) that is recognized by the host innate immune system and promotes production of pro-inflammatory cytokines, including IL-1β. However, how bacterial processing of peptidoglycan drives IL-1β production is comparatively unexplored. Here, we tested the involvement of staphylococcal glucosaminidases in shaping innate immune responses and identified …

Identification Of Conditions That Promote Biofilm Formation By Vibrio Fischeri And Elucidation Of The Underlying Signal Transduction Pathway, Courtney Noelle Dial

Dissertations

Biofilms are communities of microorganisms that have intrinsically antimicrobial properties and are difficult to treat in the clinical setting. The marine bacterium Vibrio fischeri efficiently colonizes its symbiotic squid host, Euprymna scolopes, by producing a transient biofilm dependent on the symbiosis polysaccharide (SYP), making it the perfect model system to study biofilm dynamics. In vitro, however, wild-type (WT) strain ES114 fails to form SYP – dependent biofilms. Instead, genetically engineered strains, such as those lacking the negative regulator BinK, have been developed to study SYP biofilms. Historically, V. fischeri has been grown using LBS, a complex medium containing tryptone and …

Characterization Of Mroq-Dependent Regulation Of Staphylococcus Aureus Quorum Sensing, Madison Ruth Stock

Dissertations

Gram-positive bacteria produce small autoinducing peptides (AIPs), which act to regulate expression of genes that promote adaptive traits including virulence. The Gram-positive pathogen Staphylococcus aureus generates a cyclic AIP that controls expression of virulence factors via the accessory gene regulatory (Agr) system. S. aureus strains belong to one of four Agr groups (I, II, III, and IV), and each group harbors allelic variants of AgrD, the precursor of AIP. In a prior screen for S. aureus virulence factors, the Alonzo lab identified MroQ, a putative peptidase. A ΔmroQ mutant closely resembled a Δagr mutant and had significant defects in AIP …

Investigating Putative Toxin-Immunity Pairs From A New Class Of Rhs Proteins In Pseudomonas Aeruginosa, Syed Faieq Imam

Master's Theses

Pseudomonas aeruginosa is a gram-negative, opportunistic pathogen that is ubiquitous in nature, especially in human/animal impacted environments. One of the reasons for this is the arsenal of protein systems and toxins that P. aeruginosa utilizes to mold its environment to suit its needs. Recently, we discovered a novel locus in the P. aeruginosa genome, which resembles other loci that are known to mediate interbacterial competition. Our bioinformatic analysis found this locus to be enriched in a rearrangement hotspot (rhs) motif which led us to ad-interim term the three ORFs of the loci as rhsB, rhsC, and rhsI. Furthermore, we have …

Investigating Structural And Biochemical Characteristics Of A Peptidase Required For Staphylococcus Aureus Virulence, Sagar Bhusal

Master's Theses

Staphylococcus aureus is an opportunistic Gram-positive pathogen that transiently colonizes 30% of the population at any given time. Upon breaching host skin or mucosal barriers, S. aureus can infect and cause disease in nearly all host tissues. Once inside the host, S. aureus expresses a plethora of virulence factors, mostly regulated by the Accessory Gene Regulatory (Agr) quorum sensing system, which facilitates the evasion of immune responses or directly promotes pathogenesis. The S. aureus Agr system relies on the production of a small peptide known as an auto-inducing peptide (AIP) to control virulence gene expression in response to cell density. …

Identification Of New Substrates From Pseudomonas Aeruginosa Exos, Adam V. Thota

Master's Theses

Pseudomonas aeruginosa is a gram-negative environmental bacterium that uses its intrinsic and acquired antibiotic resistance to infect patients with compromised epithelium, such as cystic fibrosis and burn wounds, and corneal keratitis. In order to cause disease, most strains of P. aeruginosa use the type three secretion system (T3SS) to disrupt cellular signaling and integrity. However, P. aeruginosa may also secrete exotoxins after invading host cells, which prolongs host cell death and maintains an intracellular niche. Of the T3 secreted effector toxins, ExoS, specifically the ADP-ribosyltransferase activity of ExoS, was shown to delay the death of invaded corneal cells, but it …

Development Of Duplex Loop-Mediated Isothermal Amplification (Dlamp) For Detection Of Carbapenem Antibiotic-Resistant Genes Kpc And Ndm, Nindi Syahputri Lubis

Chulalongkorn University Theses and Dissertations (Chula ETD)

Carbapenems are regarded as a last-resort option for treating a wide range of Gram-positive and Gram-negative bacterial infections. Unfortunately, the prevalence of carbapenem-resistant genes has been on the rise among patients. Some factors contribute to this trend, including prolonged hospital stays, prior antibiotic usage, inappropriate or insufficient antibiotic treatment, and contamination through wounds or feces. The emergence of carbapenem-resistant (CR) genes gained significant attention, particularly after 2005. These CR genes are frequently carried on mobile genetic elements such as plasmids or transposons, enabling their transmission to other bacteria. Klebsiella pneumoniae carbapenemase (KPC) and New delhi metallo-β-lactamase (NDM) stand out as …

Structural Impact Of Epstein-Barr Virus- Encoded Small Rna -1 On Its Transport And Function, Zubaida Hassan

Dissertations

Epstein-Barr Virus (EBV)-Encoded RNAs (EBERs) are two small, noncoding, structurally conserved transcripts that are expressed in millions of copies in all stages of EBV infection. Despite their abundant expression, the role of EBERs in EBV biology or pathogenesis is not well defined. However, they are associated with driving cell proliferation and improving intercellular communication via their secretion in exosomes. In spite of the pathogenic potentials of EBERs, the mechanisms involved in their transport and function remain to be elucidated. The aim of this PhD dissertation was to investigate the structural impact of EBER1 in its transport and function. The conserved …

Screening For Compounds That Affect Innate Immune Memory In Macrophages, Intan Mukti Pratiwi

Chulalongkorn University Theses and Dissertations (Chula ETD)

Innate immunity, the first line of defense against pathogens, is characterized by a rapid response, limited specificity, and lack of memory for future insults. However, recent evidence indicates that components of innate immunity, such as monocytes, macrophages, and natural killer cells, exhibit memory-like responses, known as trained immunity. Trained immunity involves metabolic reprogramming and epigenetic modifications to regulate the expression of inflammation-related genes. Dysregulation of trained immunity can lead to diseases, making it a novel therapeutic target. In this study, the effects of synthetic saccharides derived from the cell wall of Mycobacterium tuberculosis and synthetic cannabinoids on innate immune memory …

Nitrite Cycling In The Primary Nitrite Maxima Of The Eastern Tropical North Pacific, Nicole M. Travis, Colette L. Kelly, Margaret R. Mulholland, Karen L. Casciotti

OES Faculty Publications

The primary nitrite maximum (PNM) is a ubiquitous feature of the upper ocean, where nitrite accumulates in a sharp peak at the base of the euphotic zone. This feature is situated where many chemical and hydrographic properties have strong gradients and the activities of several microbial processes overlap. Near the PNM, four major microbial processes are active in nitrite cycling: ammonia oxidation, nitrite oxidation, nitrate reduction and nitrite uptake. The first two processes are mediated by the nitrifying archaeal/bacterial community, while the second two processes are primarily conducted by phytoplankton. The overlapping spatial habitats and substrate requirements for these microbes …

In Silico Analyses Of Diversity And Dissemination Of Antimicrobial Resistance Genes And Mobile Genetics Elements, For Plasmids Of Enteric Pathogens, Suad Algarni, Jing Han, Dereje D. Gudeta, Bijay K. Khajanchi, Steven C. Ricke, Young Min Kwon, Douglas D. Rhoads, Steven L. Foley

Animal Science Faculty Publications and Presentations

Introduction: The antimicrobial resistance (AMR) mobilome plays a key role in the dissemination of resistance genes encoded by mobile genetics elements (MGEs) including plasmids, transposons (Tns), and insertion sequences (ISs). These MGEs contribute to the dissemination of multidrug resistance (MDR) in enteric bacterial pathogens which have been considered as a global public health risk.

Methods: To further understand the diversity and distribution of AMR genes and MGEs across different plasmid types, we utilized multiple sequence-based computational approaches to evaluate AMR-associated plasmid genetics. A collection of 1,309 complete plasmid sequences from Gammaproteobacterial species, including 100 plasmids from each of the following …

The Type Iv Pilus Secretin Bfpb: Structural Analysis And Binding Interactions, Janay I. Little

Theses and Dissertations

Enteropathogenic Escherichia coli (EPEC) causes severe diarrhea in young children. The type IV pilus (T4P) of EPEC, known as the bundle-forming pilus (BFP), plays an important role in EPEC pathogenesis. T4Ps are a family of surface appendages that are important for adhesion, colonization, biofilm formation, virulence, twitching motility and many other functions. One essential component of the BFP system is the secretin, BfpB. Secretins are a large family of integral outer membrane proteins found in T4Ps as well as type II and type III secretion systems, and filamentous phages. Details of the secretin structure have been limited to the overall …

Treponema Denticola Synthesizes C-Di-Amp And Encodes The Cdaa-Type Diadenylate Cyclase Cdaa, Claire R. O'Brien

Theses and Dissertations

Periodontitis is a form of oral disease characterized by dysbiosis of the oral microbiome, leading to inflammation, bone resorption, and in severe cases, entire tooth loss, affecting 42% of adults in the US. One of the bacteria most associated with periodontal disease progression is Treponema denticola (Td), an oral spirochete which inhabits the mouth in small quantities during health but which can dominate the biofilms that form during periodontal disease. The ability of Td to survive in a disease environment and contribute to the progression of disease requires the use of robust signaling networks. Analysis of Td cultures …

Characterization Of The Clostridioides Difficile Glycosyl Hydrolase Ccsz, Brian Lowrance

Theses and Dissertations (Comprehensive)

Bacteria inhabit many of the harshest environments on Earth; persisting and thriving in conditions thought to be unsuitable for life. One common strategy to withstand these environments is the formation of a biofilm. Biofilm composition varies greatly, depending on the underlying community that produces it. Cellulose, a polymer consistently prevalent in biofilms, has been identified as a virulence factor in many pathogens and is suspected to be involved in pathogenesis by Clostridioides difficile. C. difficile is the #1 cause of hospital acquired diarrhea, which can range from mild to life-threatening infections. Biofilm formation is hypothesized to be involved in …

Characterizing The Rhizosphere Microbial Community Of Food Crops In A Changing Climate, Samuel Snider

Theses and Dissertations (Comprehensive)

In recent years, there have been increased occurrences of food-borne illness in Canada, which is not directly associated with animal-related products but is caused by the increasing prevalence of pathogenic outbreaks in fresh produce. This can have health and economic impacts on the agriculture industry in Canada. As such, it is essential to better understand the plant-microbe interactions of crops grown in Canada and determine how climate change may alter the relationship. Plants can promote the growth of beneficial bacteria in the rhizosphere, which can create protective competition between beneficial and pathogenic bacteria. Changes in the environment of the rhizosphere …

Functional Residues Of Cjpata, Robert Lamont

Theses and Dissertations (Comprehensive)

Antibiotic resistance in pathogenic bacteria continues to challenge clinicians and threaten the lives of infected individuals. For this reason, new classes of antibiotics or new targets for antibiotic therapy are needed to circumvent this global health crisis. In Gram-negative bacteria, the enzymes peptidoglycan O-acetyltransferase A and B (PatA and PatB), are responsible for adding acetyl groups to the C-6 hydroxyl group of N-acetyl muramic acid (MurNAc) in peptidoglycan (PG). These acetyl groups are responsible for inhibiting the activity of lysozyme from host organisms that hydrolyze the β1-4 glycosidic linkage between MurNAc and N-acetylglucosamine (GlcNAc). The acetyl groups …

Connecting Antibiotic Resistance To The Environment (Care): Introducing A Novel Framework Integrating Chemical Cross-Resistance And Place-Based Engagement To The Blue Marsh Watershed In Reading, Pennsylvania, Jill Felker

Antioch University Dissertations & Theses

Antibiotic resistance is a serious health threat around the world. Millions of individuals are infected with antibiotic-resistant bacteria yearly, and thousands die from previously curable illnesses. Although antibiotic resistance occurs naturally, misuse of antibiotics accelerates the loss of their effectiveness. Public health campaigns focusing on antibiotic awareness have not effectively communicated and educated the public on this health crisis. New efforts to combat antibiotic resistance are urgently needed. This dissertation focuses on the ecological and public health components of antibiotic resistance research that must be addressed to decelerate antibiotic resistance. A new interdisciplinary theoretical framework was developed to Connect Antibiotic …