Microbiology Commons^™

Effect Of Common Oxidative Water Treatments On Acanthamoeba Internalized Legionella, James Park

UNLV Theses, Dissertations, Professional Papers, and Capstones

Legionella pneumophila can cause pneumonic and non-pneumonic disease in humans. Infections occur from aerosolized contaminated water. This bacterium is an opportunistic intracellular pathogen able to infect both protozoans, such as Acanthamoeba polyphaga, and human macrophages. Both L. pneumophila and A. polyphaga resist commonly used water treatments, such as chlorination, but L. pneumophila has displayed greater resistance in the presence of A. polyphaga. Therefore, there is concern that L. pneumophila could become established in plumbing systems after water treatment, leading to infections. The objective of this study was to show the effect of chlorine and chlorine dioxide exposures on the survival …

Beyond Genetics: Addressing Activity In Microbial Ecology, Scott Christopher Thomas

UNLV Theses, Dissertations, Professional Papers, and Capstones

The field of microbial ecology is on the cusp of another revolution, one that uses synergy to address the limitations of previous studies. My dissertation is representative of the new era of research to come, through combining the latest technological advances with established classical methods to provide a more complete understanding of microbial ecosystems. In my first study, I evaluate the conservation of central carbon metabolic pathways and activity along a temperature and diversity gradient (60-95 ℃) through the use of 16S rRNA gene amplicon data, metagenome sequencing, and position-specific 13C-labeled metabolite probing. In my second study, I provide the …

Prokaryotic Diversity And Aqueous Geochemistry Of Subsurface Environments Of The Death Valley Regional Flow System, Joshua David Sackett

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation summarizes over four years of effort towards the completion of a Ph.D. in Biological Sciences. The work presented in this document covers a broad range of topics, but a central unifying theme is prokaryotic life in the continental subsurface. The work presented in each chapter relied heavily on cultivation-independent methods for assessing prokaryotic communities, including prokaryotic community structure reconstruction from high-throughput sequencing of 16S rRNA gene libraries and single-cell genome analysis of novel uncultivated bacteria.

Chapter 2 examines the aqueous geochemistry and prokaryotic diversity of Devils Hole, a cavernous limnocrene and sole natural habitat for the critically endangered …

Transcriptional Silencing And Anti-Silencing Of Virulence Genes In The Bacterial Pathogen Shigella Flexneri: Virb, Dna Supercoiling, And The Histone-Like Nucleoid Structuring Protein, Michael Adam Picker

UNLV Theses, Dissertations, Professional Papers, and Capstones

Transcriptional silencing and anti-silencing affect many aspects of bacterial physiology, including virulence in bacterial pathogens. In Shigella species, a group of gram-negative pathogens that cause bacillary dysentery in humans, the histone-like nucleoid structuring protein (H-NS) transcriptionally silences virulence genes found on the large virulence plasmid while VirB anti-silences these genes. However, the mechanistic details of their interplay are not fully understood. To elucidate their regulatory mechanisms, I use the icsP virulence locus, which shares a long intergenic region with the divergently transcribed ospZ gene (1535 bp from TSS to TSS). Prior to this work, two discrete H-NS binding regions had …

Screening For The Novel Cariogenic Pathogen Scardovia Wiggsiae Among Orthodontic Patients, Adam Whiteley

UNLV Theses, Dissertations, Professional Papers, and Capstones

Screening for the Novel Cariogenic Pathogen Scardovia wiggsiae among Orthodontic Patients

by

Adam Whiteley

Dr. Karl Kingsley, Examination Committee Chair Professor of Biomedical Sciences University of Nevada, Las Vegas School of Dental Medicine

The recent discovery of a novel cariogenic pathogen Scardovia wiggsiae has led many scientists and oral health researchers to re-evaluate and re-examine existing saliva repositories to determine the prevalence among patient populations. Recent efforts at this institution have used existing saliva samples to determine the prevalence among both adults and pediatric patients. These studies have revealed this organism may be found in approximately one-quarter of all samples …

Complete Sequencing And Comparative Analysis Of The Genomes Of The First Magnetotactic Gammaproteobacteria Isolated In Pure Culture: Strains Bw-2 And Ss-5, Corey Geurink

UNLV Theses, Dissertations, Professional Papers, and Capstones

The genomes of the first two discovered magnetotactic bacteria (MTB) belonging to the ammaproteobacteria, strains BW-2 and SS-51, were sequenced, sealed, annotated and compared to MTB of other phylogenetic groups. Cells of both strains are rod-shaped and biomineralize cuboctahedral and elongated octahedral crystals of magnetite, respectively, that are enveloped in a protein-embedded, lipid-bilayer membrane referred to as the magnetosome membrane or vesicle. The crystals and their associated membranes are known as magnetosomes. Magnetosome crystals consist of either magnetite (Fe3O4) or greigite (Fe3S4) and, because of their specific mineral compositions, crystal morphologies and sizes, the biomineralization processes involved in magnetosome formation …

A Potential Solution To A Poopy Problem: Bile Salt Analogs As Prophylactics Against Clostridium Difficile Infection, Jacqueline Renee Phan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Clostridium difficile infection (CDI) is a major cause of antibiotic-associated diarrhea. In 2011, over 500,000 patients were diagnosed with CDI in the United States and over 29,000 people died of CDI-related complications. With an average of $35,000 to treat a single case of inpatient CDI, cost burden to the healthcare system can reach up to $3.2 billion annually. As both hospital- and community-acquired CDI incidences rise due to the emergence of hypervirulent strains and CDI reoccurrences of up to 25%, standard treatments are rendered less effective and new methods of prevention are critical.

CDI is caused by bacteria called Clostridium …

Evaluation Of A Fluorescence Method For Quantifying Bioaerosol Concentrations On Air Quality Filter Samples, Rachel Kolberg

UNLV Theses, Dissertations, Professional Papers, and Capstones

Airborne particulate matter (PM) in outdoor environments contains many components that cause adverse human health effects. The size of the particulates determine in what manner the particles would bypass the body’s defense mechanisms to enter the respiratory system and is directly related to their health impacts. Currently the United States Environmental Protection Agency is enforcing the National Ambient Air Quality Standards (NAAQS) to regulate the annual and 24-hour average concentrations of PM2.5 and PM10 in the air. PM2.5 are fine particles with aerodynamic diameter <2.5μm, small enough to reach the deepest parts of the bronchi and lungs. PM10 include PM2.5 and larger particles with aerodynamic diameter of 2.5-10μm. Both PM2.5 and PM10 contain multiple components from multiple sources. Bioaerosols are an important component of PM, but there is limited knowledge about how bioaerosols contribute to PM2.5 and PM10 concentrations. There is also a lack of research about the incidence and prevalence of disease caused by bioaerosols and about the limits of exposure to bioaerosol particulates. The main barrier to assess bioaerosol concentrations and health-related effects is the absence of quick and inexpensive methodology for quantifying bioaerosols. This study explored the feasibility of using fluorescence microscopy to quickly quantify bioaerosols in PM2.5 and PM10 collected on polycarbonate filters. Bioaerosols were stained with a DNA marker directly on a filter, followed by fixation, microscopic imaging, and automatic counting. The method was first validated using reference samples prepared by depositing different known concentrations of E. coli onto blank polycarbonate filters. The results indicated a linear response over two orders of magnitude (R2 = 0.9) and an accuracy within ±25%. E. coli were also deposited onto selected ambient PM10 and PM2.5 filter samples to determine if pre-loaded particles would interfere with bioaerosol imaging and counting. It was found that despite an increase in uncertainty (variability), the calibration slope remained within ±10% of unity for both PM2.5 and PM10 samples. Bioaerosol concentrations in ambient samples, as quantified by this method, were on average 14% higher for PM10 than for PM2.5 acquired concurrently in a desert environment of Las Vegas, Nevada. The application of this method to other types of compliance filters, such as Teflon filters and tapes of a Beta Attenuation Monitor (BAM) were also explored in this study. By means of a high-yield approach this method is expected to facilitate bioaerosol research, support exposure and health assessments, and help refine NAAQS for PM2.5 and PM10.

Oral Microbial Burden Of Periodontal Pathogens Among Orthodontic Patients, David Jolley

UNLV Theses, Dissertations, Professional Papers, and Capstones

Objectives

Many research studies involving orthodontic patients have a natural inclination to focus on changes in levels of cariogenic pathogens after bracket placement, and very few studies examine the role of changes of periodontal pathogens – particularly among adult patients. Interestingly, recent evidence suggests that increased levels of a specific periodontal pathogen, Fusobacterium nucleatum, may elevate risk for development of colon cancer in adults through direct pathways. Based upon this new evidence, the objective of the current study was to screen saliva samples taken from orthodontic patients to determine the prevalence of periodontal pathogens, including F. Nucleatum, T. denticola, and …

Development Of The K-State (Competence) And Mutagenesis In Stressed Bacillus Subtillis Cells, Amanda Kidman

UNLV Theses, Dissertations, Professional Papers, and Capstones

Mutagenesis is central to the evolutionary process. We currently view evolution as a gradual process affecting all cells within a population. However, my project studied an underestimated part of the evolutionary process: mutations generated during stationary phase (caused by nutritional stress or growth arrest) within a subpopulation of cells. I used Bacillus subtilis, a bacterial model for cell growth and differentiation. Stationary-phase cultures of B. subtilis differentiate subpopulations that exhibit different survival strategies including competence, secondary metabolite production, biofilm formation, cannibalism, and endospore formation. The development of competence permits cells to uptake exogenous DNA and incorporate it into their genome. …

Incomplete Denitrification In Thermus Species, Chrisabelle Mefferd

UNLV Theses, Dissertations, Professional Papers, and Capstones

Members the bacterial genus Thermus have been shown to be incomplete denitrifiers, terminating with nitrite or nitrous oxide (N2O). However, the ability to carry out denitrification and the evolution of nitrogen oxide reductase genes in Thermus remains poorly understood. This study tests the hypothesis that incomplete denitrification is common in Thermus and seeks to uncover patterns in the evolution of denitrification pathways in Thermus. Denitrification capacity was determined in a collection of 25 strains representing ten species of Thermus and phylogenetic analysis was performed to determine whether denitrification genes evolved horizontally in Thermus. No strains in this study reduced nitrate …

The Role Of Mfd In Stationary-Phase Oxidative Damage Repair In Bacillus Subtilis, Katelyn E. Porter

UNLV Theses, Dissertations, Professional Papers, and Capstones

Since the 1950’s it has been shown that bacterial cells accumulate mutations even in non- dividing conditions, but how this type of mutation occurs is still highly debated. In Bacillus subtilis, Mfd, a precursor of the nucleotide excision repair (NER) system, mediates the formation of mutations in stationary-phase or non-replicating cells. In growing cells, Mfd recruits repair when RNA polymerase is stalled during transcription; it then recruits proteins from NER to repair damage. Here, we examine the hypothesis that Mfd mediates the formation of mutations by interacting with cellular components that repair reactive oxygen species (ROS), a natural byproduct of …

Biogeochemistry Of A Saline, Alkaline, Terminal Lake Ecosystem In Transition; Walker Lake, Nevada, Katherine Lynn Willever

UNLV Theses, Dissertations, Professional Papers, and Capstones

Walker Lake is a saline, alkaline, terminal lake ecosystem located in west-central Nevada. For over one hundred years, anthropogenic streamflow diversions within the Walker River Basin have ultimately led to little or no water reaching Walker Lake, the basin’s terminus for water flow. These diversions have resulted in a >46 meter decrease in the lake surface altitude and increases in salinity and dissolved salt constituents that have caused the elimination of native fish species. This study examines how the lack of freshwater inflow has altered the physical, chemical, and microbiological structure of Walker Lake during the lake’s ongoing desiccation.

Between …

Effectiveness Of Commercially-Available Cosmetic Cleaners On Cosmetics And Cosmetic Brushes, Vanessa Ortiz

UNLV Theses, Dissertations, Professional Papers, and Capstones

The complex nature of skin contributes to the microbial population present on its surface. While normal skin flora is either beneficial or has no effect on the body, there are instances where pathogenic microorganisms are present and can cause infections. Damaged skin is more susceptible to infections from these microbes. Behavioral characteristics, such as the use of cosmetics, can affect the microbial population present on the skin. Staphylococcus aureus is the organism most commonly isolated from cosmetics, and it can be responsible for conjunctivitis, impetigo, boils, and folliculitis.

There are many ways microbial contamination of cosmetics can occur, such as …

Microbial Contamination Of Ice At Food Establishments In Las Vegas, Nevada, Jerry Wills

UNLV Theses, Dissertations, Professional Papers, and Capstones

When food establishments make ice for consumption, it is important to use water free of pathogens and to employ hygienic practices. Freezing can reduce the number of culturable microorganisms present in water but does not eliminate them completely. Coliform bacteria are used as an indicator of water quality and are used to test for fecal contamination. The U.S. Environmental Protection Agency (EPA) establishes standards for drinking water, and has set a goal for zero total coliforms. Another commonly used tool to measure water quality is the heterotrophic plate count (HPC). The EPA limit for HPC is 500 colony forming units …

The Effects Of Honeybee (Apis Mellifera) Antimicrobial Peptides On Paenibacillus Larvae, Jasmin Camille Khilnani

UNLV Theses, Dissertations, Professional Papers, and Capstones

American Foulbrood Disease (AFB) is the most detrimental bacterial disease that affects honeybee larvae (Apis mellifera) worldwide. The etiological agent of AFB is the Gram-positive, spore-forming bacterial pathogen, Paenibacillus larvae. Treatment with antibiotics, specifically oxytetracycline, has led to the development of antibiotic resistance in P. larvae. Therefore, there is a pressing need for an alternative treatment method. The overall goal of this project was to test naturally occurring, active antimicrobial peptides (AMPs), which are produced in the adult honeybee, against vegetative P. larvae. These active AMPs could potentially be used as a prophylactic treatment to prevent P. larvae infection of …

Cultivation-Dependent Analysis Of Microorganisms Associated With Various Hydraulic Fracturing Fluids, Anthony Harrington

UNLV Theses, Dissertations, Professional Papers, and Capstones

The overarching goal of this study is to gain more insight to the microbial interactions associated with hydraulic fracturing by studying the culturable microorganisms present in various types of hydraulic fracturing fluids. Extraction of natural gas and other unconventional resources using hydraulic fracturing has increased in the last decade and very few studies have been conducted on the microorganisms associated with the various water types used in the process. From the very few published studies, the only cultivation-dependent method used involved determining the most probable number (MPN) of various metabolic groups, however the researchers failed to ask more in-depth questions …

Development Of A Molecular Method For Detecting The Causative Agent Of Swimmer's Itch (Trichobilharzia) In Freshwater Ecosystems, Heidi Mcmaster

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cercarial dermatitis, commonly known as swimmer's itch, is caused by penetration of larvae of the schistosome,Trichobilharzia, into the dermis and epidermis layers of the skin. Symptoms are characterized by painful swelling and itching at the site of penetration. The normal hosts for the life cycle of the schistosome are aquatic birds and aquatic snails. The most frequently used method of detection forTrichobilharziais microscopy. With increases in the occurrence of cercarial dermatitis outbreaks in freshwater in the Southwestern United States, it is becoming increasingly important to develop and standardize a molecular method for rapid detection that can assist health professionals and …

Determining The Presence Of Carbapenem Antibiotic Resistance In Clinical Isolates, Fidelis Uzoma Enyinnaya

UNLV Theses, Dissertations, Professional Papers, and Capstones

Carbapenems are β-lactam antibiotics reserved for the treatment of severe microbial infections, especially those targeting the Enterobacteriaceae. Introduced in the 1980s, carbapenems have been used successfully in hospitals, and in the 1990s resistance was discovered. Carbapenem resistance is conferred through the production of carbapenemases. In the U.S., the most common carbapenemase is Klebsiella pneumoniae carbapenemase (KPC). In 2012, the National Healthcare Safety Network reported a carbapenem resistance rate of 13.0% among Klebsiella pneumoniae infections, and indicated that the mortality rate associated with carbapenem resistant Enterobacteriaceae (CRE) infections ranged from 48.0-71.9%. According to the Food and Drug Administration (FDA), carbapenem resistance …

Isolation And Characterization Of Paenibacillus Larvae Bacteriophages For Use As A Treatment Of American Foulbrood Disease In Honeybees, Diane Gerda Yost

UNLV Theses, Dissertations, Professional Papers, and Capstones

American foulbrood disease is a destructive honeybee illness cause by the bacterial pathogen, Paenibacillus larvae. Current methods of treatment are either destructive or do not completely eradicate the infection, and as such, undertaking further research to determine the effectiveness of alternate treatment methods is of consequence.

The therapeutic use of bacteriophage that are capable of lysing host bacterial cells, or phage therapy, is one such potential treatment. Phage are viruses that infect bacteria, and are generally very host-specific. As such, targeting a pathogen would require obtaining phage specific for P. larvae. Therefore, obtaining P. larvae phage requires screening environmental samples …

The Presence Of Methicillin Resistant Staphylococcus Aureus (Mrsa) On Environmental Surfaces In Healthcare Facilities Pre- And Post-Cleaning, Aaron Thomas Hunt

UNLV Theses, Dissertations, Professional Papers, and Capstones

The emergence of antibiotic resistant bacteria is a serious public health issue affecting millions of people. Methicillin-resistant Staphylococcus aureus(MRSA) is a leading cause of healthcare acquired infections today. Research has shown that patients infected or colonized with MRSA shed the bacteria into the environment, where the bacteria can survive for long periods of time and become potential sources of infection. Currently, infection prevention efforts focus on active surveillance, hand hygiene, personal protective equipment use and antimicrobial stewardship, with less attention given to environmental cleaning. Nevertheless, environmental cleaning is essential to remove infectious agents from environmental surfaces and prevent transmission. The …

Anti-Germinants As A New Strategy To Prevent Clostridium Difficile Infections, Amber Janece Howerton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Clostridium difficileinfections (CDI) have emerged as a leading cause of hospital-associated complications. CDI is the major cause of antibiotic-related cases of diarrhea and nearly all cases of pseudomembranous colitis. The infective form of C. difficileis the spore, a dormant and hardy structure that forms under stress. Germination of C. difficile spores into toxin producing bacteria in the GI tract of susceptible patients is the first step in CDI establishment. Patient susceptibility occurs with a disruption of the natural gut microbiota by broad-spectrum antibiotics. Antibiotic treatments usually resolve CDI but refractory cases are on the rise. Of great concern is the …

Natural And Lignocellulose-Enriched Microbial Communities In Great Boiling Spring, Nv, Jessica Cole

UNLV Theses, Dissertations, Professional Papers, and Capstones

The natural microbial communities present in Great Boiling Spring were investigated and contrasted against those present after in situ enrichment with lignocellulose. High-throughput cultivation-independent DNA sequencing of the V8 region of the small subunit (SSU) rRNA gene generated a total of 274,119 quality-filtered pyrosequencing fragments. Twelve natural spring samples were analyzed, including four high-temperature water samples and eight sediment samples ranging from 87 - 62 °C. Eight lignocellulosic enrichments incubated in the spring sediment and water at two high-temperature sites were analyzed. The natural water communities were found to be extremely uneven but relatively constant throughout time. The natural sediment …

Nitrite Oxidation In Geothermal Springs: Evidence Of An Upper Temperature Limit For Thermophilic Nitrite-Oxidizing Bacteria Of 60 - 65 °C, Tara Edwards

UNLV Theses, Dissertations, Professional Papers, and Capstones

Despite growing evidence of the importance of nitrification in terrestrial geothermal environments, little is known about nitrite oxidation in these environments. In order to further our knowledge, this study combined cultivation-dependent and -independent approaches with measurements of nitrogen speciation along the outflow channels of two Great Basin geothermal springs. Enrichment cultures were inoculated with sediment slurries from sites ranging in temperature from 42 - 87 °C at the sources and along the outflows of >15 hot springs. While attempts to enrich nitrite-oxidizing bacteria (NOB) from sites greater than or equal to 61 °C were unsuccessful, NOB were enriched from five …

Effects Of Moisture Augmentation Of Municipal Solid Waste Through Addition Of Food Waste Or Wastewater Treatment Biosolids On Bio-Gas Formation For Power Generation, Jared Michael Gore

UNLV Theses, Dissertations, Professional Papers, and Capstones

An investigation into the effect of moisture augmentation by manipulation of food waste proportion or wastewater treatment plant biosolids proportion was undertaken to determine the effects on production of methane and other biogases from municipal solid waste (MSW). Laboratory microcosm experiments were performed to determine the effect of various proportions of influent waste streams on the production of biogas. Results indicated that moisture augmentation through the addition of food waste to MSW increases the overall bio-gas and hydrogen gas formed during fermentation. Moisture augmentation through addition of wastewater treatment bio-solids lead to inconclusive results. Addition of food waste to MSW …

A Polymerase Chain Reaction Method For The Detection Of Selenomonas Noxia, Arthuro Mehretu

UNLV Theses, Dissertations, Professional Papers, and Capstones

In recent studies, periodontal health has been linked to being overweight and/or obese. Among common oral bacteria, Selenomonas noxia has been implicated in converting periodontal health to disease. Selenomonas spp. have also been found in gastric ulcers, and were misdiagnosed as Helicobacter -like organisms, but no further studies were conducted. The increasing clinical and epidemiological importance of S. noxia necessitates the development of a rapid detection method. In this study, a TaqMan 16S rRNA based real-time Polymerase Chain Reaction (PCR) method was developed, optimized and evaluated for the rapid and specific detection of S. noxia . The 16S PCR assay …

Retrospective Evaluation Of Microbial Presence In Existing Saliva Repository: A Pcr Based Molecular Survey Of Oral Microbial Populations From Existing Saliva Samples, Jay Ericksen Davis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The overall purpose of this research project is to explore the link between oral health and disease in the University of Nevada, Las Vegas - School of Dental Medicine (UNLV-SDM) clinic patient population. More specifically, the population of interest is the UNLV-SDM orthodontic clinic patient population, which is mostly composed of adults, females, and minorities. The University of Nevada, Las Vegas, School of Dental Medicine, with more than 70,000 active patients and a post-graduate specialty program in Orthodontics is uniquely positioned to perform this type of oral health epidemiology survey, as well as targeted oral microbial testing among populations within …

Microbial Impacts On Endocrine Disrupting Contaminants: Las Vegas Wash And Lake Mead, Nevada, Susanna May Blunt

UNLV Theses, Dissertations, Professional Papers, and Capstones

International concern over endocrine disrupting chemicals (EDCs) has become heightened in recent years as more studies reveal their persistence in the environment and their detrimental effects on wildlife. However, little is known about the role of microorganisms in the fate and transport of these compounds in surface waters. Las Vegas Wash, a stream flowing into Lake Mead and fed primarily by treated wastewater effluent, provided a unique experimental system in which to study the role microorganisms play in the dispersal of these compounds in aquatic systems. Samples were collected from the Las Vegas Wash downstream of the Las Vegas Valley's …

Characterization And Regulation Of The Icsp And Ospz Locus In Shigella Flexneri, Krystle Lashell Pew

UNLV Theses, Dissertations, Professional Papers, and Capstones

Shigella flexneri is a gram negative, rod shaped bacterium that is the causative agent of bacillary dysentery, which is characterized by fever, abdominal pain, and bloody diarrhea. Genes essential to the pathogenicity of S. flexneri are encoded by a virulence plasmid. Shigella has evolved a complex regulatory system to regulate transcription of virulence genes. This involves two regulators, VirF and VirB, which allow the bacterium to respond to environmental stimuli and maximally exploit host niches. An additional factor impacting virulence gene regulation is H-NS, a histone nucleoid structuring protein that globally represses transcription. This work addresses the transcriptional regulation of …

Transcriptional Regulation Of Shigella Virulence Plasmid-Encoded Genes By Virb And Crp, Christopher Thomas Hensley

UNLV Theses, Dissertations, Professional Papers, and Capstones

Shigella flexneri is a species of Gram-negative intracellular pathogens that causes bacillary dysentery in humans. Shigella relies on the precise transcriptional regulation of virulence genes, encoded by a large virulence plasmid, for invasion and infection of human colonic epithelial cells. The transcription of most identified virulence genes are regulated through a cascade controlled by the primary regulator of virulence genes, VirF, and the global transcriptional regulator, VirB. Currently, few studies have addressed how individual Shigella virulence genes are precisely regulated for optimal expression during specific stages of pathogenesis and within the constraints of the regulatory cascade. This work addresses how …