Microbiology Commons^™

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 …

Hot Spring Associated Infectious Diseases In The Great Basin And Southwest, Matthew Bentz

UNLV Theses, Dissertations, Professional Papers, and Capstones

Like all bodies of freshwater, natural hot springs can harbor pathogenic microorganisms that carry the threat of infectious disease. The unique chemistry, increased temperature, and popularity for bathing may alter the risk profile of hot springs compared to other natural bodies of water. Despite this risk, the role of hot springs as a reservoir for infectious diseases remains understudied, particularly within the context of regional public health. Nevada and the Great Basin/Southwest have increasingly promoted hot springs for the purposes of tourism, and they share a strong link to the cultural heritage of the region. The unknown risk profile and …

The Roles Of Oprf In Pseudomonas Aeruginosa Biofilms, Erin K. Cassin

UNLV Theses, Dissertations, Professional Papers, and Capstones

Many bacteria form multicellular communities known as biofilms. Biofilms contain bacterial cells and a protective extracellular biofilm matrix. This matrix contains exopolysaccharides, extracellular DNA (eDNA), membrane vesicles, and proteins. The matrix proteins are far less characterized than other extracellular biofilm components. In biofilms formed by the model organism Pseudomonas aeruginosa, the protein OprF is abundant in the cellular outer membrane and the extracellular matrix. In my dissertation research, I have presented data supporting the hypothesis that the OprF protein significantly affects P. aeruginosa biofilms. By examining various strain backgrounds and the nutrient-dependent effects of glucose and sodium chloride, I demonstrate …

Investigating The Influence Of Environmental Stressors To Exopolysaccharide Production In Soil Cyanobacteria: Genomic And Physiological Perspectives, Benjy Sedano-Herrera

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cyanobacteria are photosynthetic microbes with essential roles in Earth’s ecosystems. The secretion of long–chain polysaccharides, known as exopolysaccharides (EPS), is a key trait facilitating cyanobacterial adaptation to diverse ecosystems. Genomics studies have shown that aquatic cyanobacteria harbor multiple gene copies encoding EPS export proteins, likely conferring a selective advantage in lakes or oceans. In addition, physiological experiments showed that nutrient limitation in aquatic habitats influences EPS production, affecting cyanobacterial fitness. However, whether terrestrial cyanobacteria also harbor multiple EPS-related genes and how nutrient limitation impacts their EPS production is not well understood.In the first chapter of my thesis, we investigated the …

Oral Prevalence Of Selenomonas Noxia Differs Among Orthodontic Patients Compared To Non-Orthodontic Controls: A Retrospective Biorepository Analysis, Kyle Hodges

UNLV Theses, Dissertations, Professional Papers, and Capstones

Introduction: The introduction of fixed orthodontic brackets in orthodontic therapy has the potential to significantly alter the oral microbial flora. Most orthodontic research has focused on cariogenic pathogens, while some evidence has demonstrated an increase in many known periodontal pathogens. However, little is known about the prevalence of the gram-negative periodontal pathogen, Selenomonas noxia (SN) among these patients.Methods: Using an existing saliva biorepository, n=208 samples from adult and pediatric orthodontic and non-orthodontic patients were identified and screened for the presence of SN using qPCR and validated primers. Results: In the pediatric study sample (n=89) 36% tested positive for the presence …

From Resistance To Host Response: An Integrative Study Of C. Difficile Infections, Amber Consul

UNLV Theses, Dissertations, Professional Papers, and Capstones

Clostridioides difficile infection (CDI) is a major healthcare challenge, causing severe gastrointestinal illness and significant mortality. Understanding the mechanisms of antibiotic resistance, epidemiology, and immune response in CDI is critical for developing effective treatments and prevention strategies.

This dissertation encompasses three complementary studies. The first study investigates the genetic mechanisms underlying cephalosporin resistance in C. difficile strain 630 through differential gene expression analysis. The second study provides a descriptive epidemiological analysis of C. difficile ribotypes in a Las Vegas patient population, highlighting differences between healthcare-associated (HA-CDI) and community-associated (CA-CDI) cases. The third study integrates serum analyte profiling and transcriptomic analysis …

Uvc And Planetary Habitability: Insights From Desert Lichens And Cyanobacteria, Tejinder Singh

UNLV Theses, Dissertations, Professional Papers, and Capstones

An important question in astrobiology is whether life can exist under the levels of UVC radiation found on Archean Earth, Mars, and exoplanets. We investigated this question by studying the UVC survival of colonial cyanobacterium and lichens that grow in harsh desert environments and possess natural sunscreens. We irradiated them nonstop in a desiccated state with a UVC flux closely representing the upper limit on those planets: 55-60 W/m². After irradiation, we rehydrated and assessed their survival using chlorophyll fluorometry and by counting the number of viable colonies that formed on agar plates. All three study organisms survived two to …

Probing The Ecological Functions Of Thermophiles Using Cultivation-Dependent And Cultivation-Independent Techniques, Dengxun Lai

UNLV Theses, Dissertations, Professional Papers, and Capstones

High-temperature geothermal springs are ecosystems that resemble early Earth, offering insights into the origins and early evolution of life. In these unique ecosystems, thermophilic microorganisms thrive. However, our knowledge of thermophiles remains limited. A major challenge is that many thermophiles remain uncultivated. The primary goal of this dissertation was to explore the diversity, metabolism, and ecological functions of thermophiles using cultivation-dependent and cultivation-independent approaches. Chapter 1 provides a broad overview of geothermal spring ecosystems and thermophiles, along with a roadmap of the dissertation. Chapter 2 documents a study on the response of specific thermophiles from Gongxiaoshe (GXS) Hot Spring in …

Screening Of Orthodontic Patients And Age-Matched Non- Orthodontic Samples For High-Risk Oncogenic Human Papillomavirus (Hpv) Strains, Hunter Hinton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Introduction: The human papillomavirus (HPV) is known to cause cancer in several tissues and organs, including the cervix and the oral cavity. Several oncogenic or high-risk strains have been identified, which include HPV16 and HPV18.However, other research has demonstrated that additional oncogenic, high-risk strains exist - including HPV31, HPV33, HPV35, HPV52 and HPV58, although much less is known about their prevalence. Based upon this lack of knowledge, the primary objective of this project is to address the prevalence of these strains among pediatric and adult patients through screening of saliva samples from the UNLV-SDM and orthodontic clinic populations.

Methods: The …

Quaternary Ammonium Compound Resistance Of Klebsiella Pneumoniae And Klebsiella Quasipneumoniae Strains Isolated From The International Space Station, Natasha Svetlana Sushenko

UNLV Theses, Dissertations, Professional Papers, and Capstones

The International Space Station (ISS) has been continuously inhabited for twenty-three years and harbors a diverse population of microorganisms under conditions of microgravity, elevated radiation, and relative isolation, including Biosafety Level 2 (BSL-2) opportunistic pathogens. To sanitize surfaces on the ISS, astronauts use a combination of four antimicrobial quaternary ammonium compounds (QACs). As the stresses of space flight are known to stimulate virulence and antimicrobial resistance in bacteria, the frequent use of QAC disinfectants on the ISS is of concern to NASA. This not only poses risks to astronauts during future long-term space travel, but there is also a concern …

Biochemical Characterization Of Fsa1572 From Fervidibacter Sacchari, The First Hyperthermophilic Gh50 With Β-1, 4-Glucanase Activity, Jonathan Covington

UNLV Theses, Dissertations, Professional Papers, and Capstones

The bacterium Fervidibacter sacchari is an aerobic hyperthermophile that catabolizes various polysaccharides and is the only cultivated member of the class Fervidibacteria within the phylum Armatimonadota. Among its glycoside hydrolase (GH) cache is an enzyme from GH family 50 (GH50), an understudied family with only 25 characterized representatives and two known activities from 1,518 predicted members in the Carbohydrate-Active EnZyme (CAZy) Database. Here, we expressed, purified, and functionally characterized an extracellular GH50 from F. sacchari called Fsa1572. Using colorimetric assays, we show it has novel β-1,4-glucanase activity and only weak agarose activity that is typical for GH50 enzymes. The purified …

Poop! There It Is! Anti-Germinants And Biological Variables As Modulators Of Clostridioides Difficile Infection (Cdi), Jacqueline Renee Phan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Clostridioides difficile infection (CDI) is a major cause of antibiotic-associated diarrhea. Due to its insidious nature, the Centers for Disease Control and Prevention (CDC) has declared CDI an urgent threat. A key characteristic of C. difficile is its ability to form dormant spores that act as the infectious vehicles for disease. In the gut, spores recognize bile salts to germinate into toxin-producing cells.Dysbiosis of the gut microbiome is a key factor in allowing the C. difficile spores to germinate. Normal gut microbiota naturally protects from CDI. However, biological variables such as diet and sex have been found to modulate to …

Desert Spring Prokaryotes And Benthic Macroinvertebrates: Geological And Ecological Controls, Ariel D. Friel

UNLV Theses, Dissertations, Professional Papers, and Capstones

Desert springs are aquatic oases, being considered among the most diverse and imperiled ecosystems on Earth. Despite the ecological significance and threatened status of desert springs, few studies have surveyed the microorganisms in these systems or their interactions with other community members. The primary goal of this dissertation was to describe the major controls influencing the community ecology of prokaryotic and BMI communities in cold- and moderate-temperature desert springs of the southern hydrographic Great Basin. Chapter 1 provides a broad overview of spring ecosystems and of each chapter included in this dissertation. Chapter 2 documents the first-ever, regional-scale survey of …

Effects Of Cations And Dipicolinic Acid On B. Anthracis Spore Physiology And Cytotoxicity, Chandler P. Hassan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Inhalation of Bacillus anthracis spores leads to the most severe form of anthrax. Following phagocytosis by alveolar macrophages, spores germinate inside the phagolysosome. The mechanism used by the newly germinated B. anthracis cells to survive within macrophages is not completely understood.B. anthracis spores contain large concentrations of calcium in complex with dipicolinic acid (Ca-DPA). Upon germination, the cell excretes the large depot of Ca-DPA. DPA is an amphipathic molecule that could act as a buffer and modulate phagolysosome acidification. Intracellular calcium overload can disrupt signaling pathways required for normal macrophage function and trigger cell death. We hypothesized the release of …

Oral Prevalence Of Akkermancia Muciniphila Among Pediatric And Adult Orthodontic And Non-Orthodontic Patients, Ching Shen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Akkermansia muciniphila (AM) is one of many highly abundant intestinal microbes that influences homeostasis and metabolic disorders and may also play a role in oral disorders. However, there is little evidence regarding the oral prevalence of this organism. Based upon this lack of evidence, the primary goal of this project is to survey an existing saliva repository to determine the overall prevalence of this organism and any associations with demographic or patient characteristics (age, sex, body mass index, race/ethnicity, orthodontic therapy). Using an approved protocol, a total n = 141 pediatric samples from an existing saliva repository were screened using …

Long-Range Regulation By The Shigella Virulence Gene Regulator, Virb, Cody Cris

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nucleoid-structuring proteins (NSPs) in bacterial cells can exert gene regulatory effects over great distances on DNA. This contrasts with the traditional view of bacterial transcriptional regulation, where transcription factors bind cis-acting regulatory sites proximal (<250 bp) to promoters to influence gene expression. In Shigella species, the histone-like nucleoid-structuring protein (H-NS) transcriptionally silences many genes on the large (~220 kb) virulence plasmid. During host colonization, however, silencing by H-NS is alleviated by the anti-silencer protein, VirB, which remodels the H-NS:DNA complex. This transcriptional anti-silencing is mediated by VirB:DNA interactions and the modulation of DNA supercoiling, which lead to the up-regulation of virulence genes. VirB is a central regulator of Shigella virulence, but the mechanistic basis for transcriptional regulation is incompletely characterized. Here, I focus on the potential for VirB to regulate transcription from remotely located DNA binding sites. Employing complementary in vivo approaches, I assessed the spatial stringency of the VirB binding site and elucidated how varying cellular VirB levels impacts regulation over different distances. I also evaluated how a molecular roadblock on DNA influences remote regulation by VirB. Additionally, I developed control tools to validate the ability of VirB to spread along DNA, an activity of VirB that putatively drives transcriptional regulation. These data are consistent with transcriptional anti-silencing being driven by VirB spreading along DNA. Overall, these findings highlight how VirB is not a conventional transcriptional regulator and broaden our perspective on transcriptional control in bacteria. Furthermore, this work contributes to our understanding of long-range gene regulatory effects, which are frequently overlooked and poorly characterized in bacteria.

Calcite Spherulite Formations And Their Controls In Halophilic Bacterial Cultures, Zakaria Jibrin

UNLV Theses, Dissertations, Professional Papers, and Capstones

This study arose from an accidental discovery of calcite spherulites forming on colonies of various halophilic bacteria grown on solid Luria-Bertani medium made containing water from a brine pool in Death Valley, their natural habitat. Further studies with a large spherulite forming bacteria, Pseudoalteromonas haloplanktis, showed that calcite precipitation conditions were the consequence of bacteria using amino acids as a source of carbon and energy, a metabolism that produces NH3 and CO2 waste products. NH3 raises the pH of the medium, turning CO2 into CO32-. Calcium in the natural brine combines with CO32-. The resulting spherulitic calcite precipitation is nano-acicular …

Taxonomic And Physiological Insights Into Novel Bacterial Class Fervidibacteria, Nancy Nou

UNLV Theses, Dissertations, Professional Papers, and Capstones

Recent studies incorporating cultivation-independent techniques to assess microbial communities, namely metagenomics and single-cell genomics, have pushed the proposed number of bacterial phyla from less than 50 to over 100. One such lineage is the candidate bacterial phylum Fervidibacteria, a strictly thermophilic group that has been identified in terrestrial geothermal springs in North America, Asia, and Antarctica through DNA sequencing. By analyzing 62 medium- and high-quality genomes and through cultivation-dependent experiments, this study serves to set up taxonomy and describe physiology within the taxon. Over the course of this study, we propose Candidatus Fervidibacteria should be reclassified as novel class Fervidibacteria …

Describing Bacterial Mutagenic Hotspots And Signatures Along With The Factors That Drive Them, Carmen Vallin

UNLV Theses, Dissertations, Professional Papers, and Capstones

In my dissertation work, I investigated bacterial mutagenesis. I asked: where do mutations occur in the bacterial genome? What types of mutations occur? What factors promote or prevent mutations? And lastly, how do the answers to these questions change depending on the bacterial life cycle (When)? I used Bacillus subtilis, a Gram-positive bacterium belonging to the phylum Firmicutes, and Escherichia coli, a Gram-negative bacterium belonging to the phylum Proteobacteria, to answer these questions. B. subtilis and E. coli are model systems that have been used to gain insights into fundamental processes of mutations and evolution for nearly ~8 decades. Here, …

Analysis Of 316 Omnitrophota (Op3) Genomes Reveals A Diverse And Ubiquitous Candidate Phylum Of Putative Syntrophs, Predators, And Free-Living Nanobacteria Encoding Giant Open-Reading Frames., Cale O. Seymour

UNLV Theses, Dissertations, Professional Papers, and Capstones

Candidate bacterial phylum Omnitrophota has never been isolated and is poorly understood. In this study, we explored the genomics, phylogeny, taxonomy, distribution, cell size, and predicted physiology of Omnitrophota based on 316 genomes. Phylogenomic concordance identified seven classes accommodating 144 species. Calibration of genome-based taxonomy to ribosomal SSU profiling revealed most Omnitrophota classes are prevalent in the Earth Microbiome Dataset, particularly in soils and sediments. Fluorescence-activated cell sorting and differential size filtration experiments showed ultra-small (<400 >nm) cells are common across the phylum, as are parasitism-related genes, including a conserved tight adherence (Tad) complex and ATP/ADP translocase. However, nucleotide and …

Comparing The Incidence And Prevalence Of Oral Microbial Pathogens Selenomonas Noxia And Streptococcus Mitis Within The Unlv-Sdm Clinical Patient Population, Namgu Kim

UNLV Theses, Dissertations, Professional Papers, and Capstones

Introduction: Selenomonas noxia (SN) is a gram-negative, anaerobic bacteria, which contributes to development and progression of periodontal disease. Some evidence now suggests Streptococcus mitis (SM), a gram-positive, facultative bacterium contributing to the etiology of dental caries and periodontal disease, may also influence the prevalence of SN within subgingival complexes. Based upon the overall lack of prevalence data, the objective of this study was to evaluate presence of SN and SM using qPCR among saliva samples taken from pediatric, adult, and orthodontic dental school clinics.

Methods: This study involved a retrospective analysis of previously collected saliva samples from an existing biologic …

Genomic Analysis Of Paenibacillus Larvae Bacteriophages, Casey Stamereilers

UNLV Theses, Dissertations, Professional Papers, and Capstones

American Foulbrood is the most destructive bacterial infection of the honeybee (Apis mellifera) and is caused by the Gram-positive, spore forming bacterium Paenibacillus larvae. Current treatment methods rely on antibiotics, but antibiotics treatments are experiencing a reduction in efficacy due to the recent rise in antibiotic resistant strains of P. larvae. This has been a major catalyst for exploration of alternative treatment methods. Phage therapy is an alternative treatment method that uses viruses that exclusively infect bacteria, known as bacteriophages (phages), to combat bacterial infections. Several experimental studies have shown that phages P. larvae phages are effective at lysing P. …

Implications Of The Evolutionary Past On The Activities Of Virb: A Key Transcriptional Regulator Of Virulence Genes In Shigella Flexneri, Jillian Nicole Socea

UNLV Theses, Dissertations, Professional Papers, and Capstones

Shigella species are bacterial agents that are the leading cause of diarrheal diseases, the second leading cause of child mortality worldwide. One key protein in Shigella is VirB, a transcriptional regulator of virulence genes that is essential for pathogenicity. VirB functions to antagonize H-NS, a histone-like nucleoid structuring protein that silences many genes found on the large virulence plasmid (pINV). The interplay between H-NS, the silencer, and VirB, the anti-silencer, is fundamental for Shigella virulence. Furthermore, this mechanism of gene regulation appears widespread in many bacteria including other enteric pathogens.

The goal of my dissertation was to explore the activities …

Transcriptional Control Of Virulence Genes In The Bacterial Pathogen Shigella Flexneri, Joy Asami Mckenna

UNLV Theses, Dissertations, Professional Papers, and Capstones

Shigella species, the causal agents of bacillary dysentery, use a type III secretion system (T3SS) to inject two waves of virulence proteins, known as effectors, into the human colonic epithelium to subvert host cell machinery. Transcriptional regulation of these virulence genes is controlled by the three-tiered VirF/VirB/MxiE signaling cascade. Of these, VirB has the largest regulon (~50 genes); however, VirB regulatory properties are poorly understood. To date, VirB is known to function to counter or 'anti-silence' transcriptional silencing mediated by the histone-like nucleoid structuring protein H-NS. To better understand VirB regulation, my colleagues and I chose to better define the …

Oral Localization Of Scardovia Wiggsiae, Graydon Ramos Carr

UNLV Theses, Dissertations, Professional Papers, and Capstones

Early childhood caries is one of the most prevalent diseases in the United States among children. The formation of caries is a complex, multifactorial process that is still being studied. Researchers have thought for years that Streptococcus mutans was the primary causative agent of early childhood caries. The recent discovery of a novel cariogenic pathogen, Scardovia wiggsiae and its significant contribution to the etiology of early childhood caries has led oral health researchers to re-evaluate this microorganism and its link to this disease. While there have been several projects undertaken within the University of Nevada, Las Vegas School of Dental …

The Influence Of G4 Dna Structures On Stationary Phase Mutagenesis In Bacillus Subtilis, Tatiana Ermi

UNLV Theses, Dissertations, Professional Papers, and Capstones

Until the late 1980’s it was widely understood that bacterial variance emerges randomly during growth. Research that followed has convincingly shown evidence for mutations arising in non-growing conditions, a phenomenon known as stationary-phase mutagenesis. In Bacillus subtilis, an elegant mutagenic mechanism has been elucidated in non-growing cells that biases mutations to transcribed regions of a subpopulation. One interesting possibility is that mutations can be further biased to hotspots within genes through alternate DNA structures known as non-B DNA. Non-B DNA have been linked to genomic instability and disease in humans, lesser is known about its role in bacteria. Here we …

Rapid Detection Of Toxin-Producing Cyanobacteria, Timothy Alba

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lake Mead provides drinking water to millions of people in Nevada, California, and Arizona. In 2015, the Southern Nevada Water Authority detected the cyanobacteria-produced toxin microcystin in the lake for the very first time. This toxin is lethal in large doses, and in small doses it causes a myriad of serious health effects. Detecting microcystin directly is a time-consuming and expensive process that requires liquid chromatography tandem mass spectrometry or immunological analyses, which require a full day or more to process samples. In order to provide water managers with the methodology for a toxin monitoring plan, this work developed a …

The Significance Of Mfd And Oxidative Damage In Stationary-Phase Mutagenesis In Bacillus Subtilis, Holly Anne Martin

UNLV Theses, Dissertations, Professional Papers, and Capstones

The process of stationary-phase mutagenesis, also known as adaptative or stress-induced mutagenesis, is a phenomenon where bacterial cells accumulate mutations in non-replicative conditions. This process has mainly been studied in Escherichia coli and Bacillus subtilis; however, the underlying mechanisms found in each of these systems differ. Here, I use B.msubtilis to study previously understudied aspects of stationary-phase mutagenesis. In this dissertation, I describe work that has led to three major discoveries which are described below.

First in B. subtilis, Mfd is important for stationary-phase mutagenesis and its mutagenic function at regions of the genome that are transcriptionally upregulated has been …

The Perplexing Paradox Of Clostridioides (Clostridium) Difficile Infection (Cdi) - Analysis Of Anti-Germinants As Part Of Cdi Prophylaxis, Christopher Yip

UNLV Theses, Dissertations, Professional Papers, and Capstones

Clostridioides (Clostridium) difficile infections (CDI) have become the leading cause of nosocomial antibiotic-associated diarrhea worldwide. Under normal circumstances, bacteria found in the gastrointestinal tract provide a barrier against C. difficile colonization. Upon antibiotic therapy, the protective barrier is lost as the microbial community becomes depleted thus providing the opportunity for C. difficile to colonize the human gut. Exposure to taurocholate, a bile acid produced within the mammalian gastrointestinal tract, causes C. difficile spores to begin their transition, a process known as germination, from metabolically dormant structures to toxin-producing cells. As germination is required for the onset of CDI, anti-germination compounds …

Prevalence Of Aggregatibacter Actinomycetemcomitans And Fusobacterium Nucleatum Among Clinical Orthodontic Saliva Samples, Jason Robert Klingler

UNLV Theses, Dissertations, Professional Papers, and Capstones

Changes to the oral microflora occur when there are shifts in the levels of the numerous bacterial species. Changes in bacterial load occur in health, disease, and dental treatments such as orthodontics and can be detected through saliva. Many studies dealing with saliva have centered around detecting bacteria known for correlation with chronic periodontitis and caries. Fewer have focused on bacterial species that contribute to microbial shifts not strictly correlated with disease. Measuring the degree of disease progression or future susceptibility is not always possible with traditional clinical parameters alone.

Aggregatibacter actinomycetemcomitans (AA) is a bacterial strain that serves as …