Microbiology Commons^™

Assessment Of A Microbicide Candidate Among A Diverse Cohort Of Urban Southern Us Women And Their Male Sexual Partners, Paula M. Frew, Kimberly Parker, Takeia Horton, Brooke Hixson, Lisa Flowers, Frances Priddy, Lisa Grohskopf, Christine Mauck, Kimberly Workowski

Environmental & Global Health Faculty Research

Background: This mixed methods study reports on product acceptance from a Phase I clinical trial of a candidate non-nucleoside reverse transcriptase inhibitor (NNRTI) vaginal microbicide product (UC781). The product was evaluated in the context of a Phase I clinical trial in an area characterized by high HIV prevalence among minority women. The findings will inform the development of an acceptable microbicide that will address the needs of diverse women and their partners. Methods: This is a mixed methods study of 34 racially and ethnically diverse female participants and 10 male partners in Atlanta, Georgia. Chi-square tests for marginal homogeneity and …

Survey Of Glycerol Dialkyl Glycerol Tetraethers (Gdgts) In Nevada And California Hot Springs And Selected T Thermophiles, Julienne J. Paraiso, Amanda Jean Williams, Brian P. Hedlund, Chuanlun L. Zhang

McNair Poster Presentations

Glycerol dialkyl glycerol tetraethers (GDGTs) are core membrane lipids of many Archaea and some Bacteria found ubiquitously in soils and in many aqueous environments. Here, we examined the GDGT concentration in forty sediment samples from geothermal hot springs in the Great Basin (USA). Sediment samples were collected in tandem with extensive geochemical and site characterization. Hot spring temperatures ranged from 31 to 95°C and pH values from 6.8 to 10.7. Parametric Pearson's correlation coefficients and nonparametric Spearman's rho values were calculated to identify significant correlations between GDGT profiles and geochemical analytes. Isoprenoidal GDGTs (iGDGTs) negatively correlated with pH and positively …

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 …

Combination Of Virb Binding Site Mutations To Evaluate Collective Impact On Icsp Promoter Activity In Shigella Flexneri, Pashtana Usufuzy, Juan C. Duhart, Maria I. Castellanos, Helen Wing

Undergraduate Research Opportunities Program (UROP)

Shigella flexneri is a gram-negative, invasive bacterial pathogen that afflicts the human colonic epithelium, causing shigellosis, an illness triggering severe dysentery. The World Health Organization cites the disease burden of shigellosis near 90 million episodes and 108,000 deaths per year.

The motility and spread of Shigella is modulated by icsP, a virulence gene. The transcription factor VirB positively regulates many virulence genes encoded by the Shigella virulence plasmid. Two distal binding sites of VirB have been shown to regulate the promoter activity of icsP, despite their location of more than 1 kb upstream of the transcription start site. Five VirB …

Identification Of Nitrifying Bacteria Contained In A Commercial Inoculant Using Molecular Biology Techniques, Anthony Harrington, John Perry, Penny S. Amy

Undergraduate Research Opportunities Program (UROP)

Nitrifying bacteria play an important role in aquatic and terrestrial environments through the nitrogen cycle. Nitrification, one of the processes of the nitrogen cycle, refers to the oxidation of ammonia to nitrate. This process requires two types of chemoautotrophic bacteria, ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB). These bacteria are essential in maintaining an optimal environment for plants and aquatic organisms, such as fish. Current applications of nitrifiers include: inoculants for aquariums, biofertilizers, and nitrogen removal in wastewater treatment plants. This study wants to identify a consortium of nitrifers that can be used to produce sufficient nitrate for plants in …

Biological Effects On Serpentinite Weathering, Mary H. Evert, Julie Baumeister, Elisabeth Hausrath

Undergraduate Research Opportunities Program (UROP)

Serpentinites, perhaps more than any other rock type, control the composition and evolution of the development of the surrounding ecosystems. The bulk chemistry of serpentinite rocks, high in Mg and trace elements, and low in nutrients such as Ca, K, P, and N, causes an extreme and stressful environment for ecosystems. However, the role that those serpentine ecosystems play in development of serpentine soils has not been examined.

Due to the unusual chemistry of serpentine soils, serpentine ecosystems have deeper and better-developed root systems than other ecosystems. The rhizosphere of serpentine systems, documented to produce abundant organic acids and siderophores, …

Inactivation Of Spo0a Gene Increases Stationary Phase Mutagenesis In Bacillus Subtilis, Denisse Reyes, Amanda Prisbrey, Holly Martin, Eduardo Robleto

Undergraduate Research Opportunities Program (UROP)

Stationary phase mutagenesis occurs when a population of cells acquires mutations conferring escape from nongrowing or stress conditions. This type of mutations is observed in nutritionally starved cells. Because the mutations occur after the onset of stress and in cells that are in non-replicative conditions, elucidating the underlying mechanisms contributes novel views to the process of evolution and apply to the formation of cancer in human cells and antibiotic resistance in microbial pathogens. Studies have shown that in Bacillus subtilis, the Mfd protein which is a transcription repair coupling factor is necessary for this phenomenon to occur. Here, we investigate …

Synthesis Of Chimeric Receptors Essential For Spore Germination, Christopher Yip, Christian Ross, Eduardo Robleto, Ernesto Abel-Santos

Undergraduate Research Opportunities Program (UROP)

Various species of bacteria have been reported to form an endospore, a metabolically dormant cell, during times of nutrient deficiencies and extreme stress. These said structures are outstandingly resistant to harsh chemicals, extreme temperatures, and can revert back to a metabolically active cell, through a process known as germination, when the necessary conditions are met. The rigid membrane of the endospore contains various germination (Ger) receptors which sense the external environment for necessary metabolites and germinants. Ger receptors are encoded by tricistronic operons that produce three distinct membrane proteins, the A, B, and C subunits. Although the function of the …

Dna Secondary Structures And Their Contribution To Mutagenesis In B. Subtilis Stationary Phase Cells, Carmen Vallin, Holly Martin, Christian Ross, Ronald Yasbin, Eduardo Robleto

Undergraduate Research Opportunities Program (UROP)

It is widely known and accepted that the cause of many mutations in cells are generated during the replication process of actively dividing cells, however more recent research has shown that mutations also arise in non growing conditions, a phenomenon known as stationary phase mutagenesis. Much of what is known come from studies in eukaryotic and bacterial models. It has been proposed that in non~growing cells, the process of transcription plays an important role in mutagenesis. We test the hypothesis that DNA secondary structures, formed during transcription, promote mutagenesis. The transcription-generated structures are speculated to be prone to mutations by …

A Spatial And Temporal Analysis Of Microbial Communities In Great Boiling Spring, Nevada, U.S.A., Jessica K. Guy, Joseph P. Peacock, Jeremy A. Dodsworth, Tanja Woyke, Tijana G. Del Rio, Brian P. Hedlund

Undergraduate Research Opportunities Program (UROP)

Great Boiling Spring (GBS) is a large, circumneutral, long residence time geothermal spring in the US Great Basin. Twelve samples were taken from four different sediment sites and the planktonic community in the bulk water of GBS on up to four different dates. Microbial community composition and diversity was assessed by using a barcoded, improved universal primer set targeting the V8 portion of the 16S rRNA gene and PCR. Over 200,000 products were sequenced using the Roche 454 GS FLX Titanium System. Sediment and planktonic microbial communities were distinct with very little overlap, regardless of the sampling location or temperature. …

Regulation Of The Shigella Flexneri Icsp Gene And H-Ns Dependent Repression, Rosa Ojeda, Amanda Wigley, Dustin Harrison, Helen Wing

Undergraduate Research Opportunities Program (UROP)

The gram negative bacterium Shigella flexneri is known to cause dysentery in humans and primates. In order to help prevent the spread of shigellosis, gene regulation must be understood. Studies show that the virulence genes in S .flexneri are thermo regulated. At 30°C histone-like nucleoid structuring protein (H-NS) represses transcription of virulence genes and at 37°C VirB derepresses virulence genes. One of the genes that contribute to the virulence of S. flexneri is icsP. My project focuses on the regulation of the S. flexneri icsP gene and has two main goals. The first is to identify the sequence of H-NS …

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 …

Vertical Transmission Of West Nile Virus In Culex Spp. Mosquitoes Of Clark County, Nevada, Vivek K. Raman

UNLV Theses, Dissertations, Professional Papers, and Capstones

West Nile Virus (WNV) is an RNA arbovirus that cycles between mosquitoes and birds, but also infects and causes disease in humans, horses and other vertebrate species. Although most infections are asymptomatic, WNV has emerged as the most common cause of epidemic meningoencephalitis in North America and the leading cause of arboviral encephalitis in the United States.

Mosquitoes of the genus Culex are the most active vectors of WNV in North America. Approximately 85% of human WNV infections in the United States occur in late summer with a peak number of cases in August and September. Vertical transmission is defined …

Time Will Tell: Community Acceptability Of Hiv Vaccine Research Before And After The "Step Study" Vaccine Discontinuation, Paula M. Frew, Mark J. Mulligan, Su-I Hou, Kayshin Chan, Carlos Del Rio

Environmental & Global Health Faculty Research

Objective This study examines whether men-who-have-sex-with-men (MSM) and transgender (TG) persons’ attitudes, beliefs, and risk perceptions toward human immunodeficiency virus (HIV) vaccine research have been altered as a result of the negative findings from a phase 2B HIV vaccine study. Design We conducted a cross-sectional survey among MSM and TG persons (N = 176) recruited from community settings in Atlanta from 2007 to 2008. The first group was recruited during an active phase 2B HIV vaccine trial in which a candidate vaccine was being evaluated (the “Step Study”), and the second group was recruited after product futility was widely reported …

The Small Regulatory Rna Ryhb Regulates Icsa Expression In Shigella Flexneri, Nick Egan, Helen J. Wing

Undergraduate Research Opportunities Program (UROP)

Shigella flexneri is a gram negative non-motile, non-spore forming, rod-shaped bacterium responsible for bacillary dysentery in humans. The master regulator, VirF, initiates a cascade of virulence gene activation by acting as a transcription factor for the gene encoding the global regulator, VirB (1). Production of VirB is also negatively regulated by the regulatory small RNA (sRNA), RyhB 2). Regulatory sRNAs are untranslated RNA molecules involved in the regulation of both transcription and translation. RyhB, a 90 nt sRNA, was first identified in E. coli and subsequently found in all Shigella species. In Shigella this sRNA is maximally expressed in response …

Antibiotic Resistance In Bacillus Subtilis As Affected By Transcriptional Derepression And The Stringent Response, Brandon Eisinger, Ronald E. Yasbin, Eduardo A. Robleto

Undergraduate Research Opportunities Program (UROP)

Bacterial cells under conditions of starvation or prolonged non-lethal selective pressures accumulate mutations in highly transcribed genes. This process is part of cellular programs to increase genetic diversity in conditions of stress, also known as stationary phase or stress-induced mutagenesis. This experiment investigated mutation frequencies for antibiotic resistance as affected by the stringent response. The stringent response is a global cellular process that initiates at the cessation of growth and mediates changes in gene expression that repress synthesis of ribosome components. We used Bacillus subtilis strains that differ in RelA proficiency. The relA gene controls the synthesis of (p)ppGpp, the …

Examination Of Germination Receptors Of B. Subtilis And B. Megaterium, Shruti Patel, Alessio Luinetti, Ernesto Abel-Santos, Eduardo Robleto

Undergraduate Research Opportunities Program (UROP)

Many bacterial species including those in the Bacilli group form spores as a mechanism to survive harsh conditions such as extreme temperature, radiation, chemicals, and nutrient starvation. By forming spores, they can remain metabolically dormant for an extended period and revert to their vegetative form when environment becomes favorable. This resumption of metabolism and growth is marked by a process called germination that is triggered by exogenous nutrients such as amino acids, sugars, and nucleotides. The (Ger) germination receptors that are postulated to respond to these germinants, in the case of B. subtilis and B. megaterium, are a complex of …

Evaluating Snow Microbial Assemblages, Jenny Lam, Jessica K. Guy, Ryan Brock, Matt Oates, Alison E. Murray

Undergraduate Research Opportunities Program (UROP)

Psychrophiles are organisms that grow optimally below 20C (1). The US Great Basin is home to many mountain peaks with an abundance of alpine snow environments perfect for psychrophilic habitation. We analyzed samples from three different locations, Wheeler Peak, Pacific Crest Trail, and Mount Conness, characterizing and comparing the psychrophilic communities at varying depth intervals in the snow. Polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) showed no notable difference in community structure with depth, but there was a distinct difference when comparing different snow environments (i.e. shaded vs. full sun exposure). The chlorophyll concentration decreased as the …

Evaluation Of Virb Binding Site Contribution To The Regulation Of The Icsp Promoter In Shigella Flexneri, Juan C. Duhart, Maria I. Castellanos, Helen J. Wing

Undergraduate Research Opportunities Program (UROP)

Shigella species are gram-negative, rod-shaped bacteria that are closely related to Escherichia coli. Virulent Shigella spp. are intracellular pathogens that invade, replicate and spread through epithelial cells of the lower intestine and cause bacillary dysentery in humans. This disease is characterized by a robust inflammatory response that results in fever, abdominal pain, and bloody diarrhea (3). According to the CDC, approximately 14,000 cases are reported each year in the United States alone. This number however, does not reflect the actual incidence of this disease as many cases go unreported. The molecular pathogenesis of these bacteria lies in the large virulence …

Modifying The Amino Acid Sequence In The Surface-Exposed Loops Of The Omptin Family Of Proteins To Determine Their Effect On Function, Natiera Magnuson, Eun-Hae Kim, Christian Ross, Helen J. Wing

Undergraduate Research Opportunities Program (UROP)

The omptin family of proteins consists of proteases which lie in the outer membrane of some gram-negative, pathogenic bacteria such as Escherichia coli (OmpT), Shigella flexneri (IcsP), Salmonella typhimurium (PgtE), and Yersinia pestis (Pla). These proteases are highly conserved, sharing approximately 50% sequence identity and a β-barrel shape (fig. 1D). The differences in the structure of these four proteins are in the surface-exposed loop region surrounding the active site, but not in the active site itself [4]. These proteases are important for the virulence of many bacteria. For example, OmpT of E. coli cleaves an antimicrobial peptide secreted by epithelial …

Transcriptional Regulation Of The Shigella Flexneri Icsp Promoter: Silencing And Anti-Silencing By H-Ns And Virb, Dustin Harrison

UNLV Theses, Dissertations, Professional Papers, and Capstones

Shigella species are gram-negative intracellular pathogens that cause bacillary dysentery in humans. Many genes required for virulence of Shigella are carried on a large 230 kb plasmid and many of these are under the transcriptional control of the histone-like nucleoid structuring protein (H-NS) and by the major virulence regulator VirB. At the non-permissive temperature of 30⁰C, H-NS represses transcription, while at 37⁰C VirB alleviates this repression. This mechanism of gene regulation has been coined "silencing/anti-silencing" and is commonly found in many important bacterial pathogens including Salmonella spp. and Yersinia spp. The icsP gene, encoded by the Shigella virulence plasmid, is …

Bacillus Cereus And Bacillus Anthracis Germination Kinetics: A Michaelis-Menten Approach, Helen Luu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Bacillus species are rod-shaped, gram-positive bacteria that are capable of producing endospores. In this dormant stage, the endospores can persist in hostile physical and chemical environments. Once conditions become favorable, the spores germinate into actively dividing cells, vegetative cells. Germination is a crucial step for the pathogenicity of the Bacilli in affecting a host organism.

Our study applies mathematical approaches to spore germination to determine whether the binding of one germinant will affect the binding of another germinant. We pursued this approach with two different species, B. cereus and B. anthracis, both pathogenic organisms. B. cereus is a widely known …

The Role Of Transcription In Stationary Phase Mutagenesis In Bacillus Subtilis, Holly Anne Martin

UNLV Theses, Dissertations, Professional Papers, and Capstones

Stationary phase mutagenesis, also known as stress-induced or adaptive mutagenesis, is defined as the accumulation of mutations during conditions of no net growth or conditions of stress. This process has been implicated in acquiring antibiotic resistance and evasion of host immune responses in microbial pathogens and in the generation of mutations that lead to neoplasia in animal cells. Previous work has shown that defects in DNA synthesis and repair systems contribute to the formation of adaptive mutations; however the role of transcription in the accumulation of mutations is still being examined. It is speculated that transcriptional derepression leads to an …

Exploring Diversity Of Nitrate Reducing Thermophiles In Nevada Hot Springs, Jenny Lam, Jeremy A. Dodsworth, Brian P. Hedlund

Undergraduate Research Opportunities Program (UROP)

High rates of denitrification have been measured in Nevada geothermal hot springs, but little is known about the thermophiles that contribute to this activity. We hypothesize that heterotrophic bacteria in the genus Thermus are the most important denitrifiers in the springs. Alternatively, other microorganisms including chemolithotrophs may also be important. To test these hypotheses, several different strategies will be used to try to enrich and isolate nitrate-reducing microorganisms. Isolates will be identified by 16S rRNA gene PCR and sequencing. Subsequently, representative isolates will be chosen for nitrate reductase gene (narG) sequencing and for studies on the kinetics of nitrate reduction …

Baseline Microbial Characterizations Of An Imperiled Aquatic Diversity Hotspot: Ash Meadows National Wildlife Refuge, Jessica Newburn, Jim Bruckner, Jenny C. Fisher, Duane P. Moser

Undergraduate Research Opportunities Program (UROP)

Located in the discharge zone of the Death Valley Flow System, Ash Meadows National Wildlife Refuge is a spring-fed desert oasis and biodiversity hotspot about 90 miles northwest of Las Vegas. These critical wetlands are potentially threatened by groundwater pumping, exotic species invasions, and climate change. Although a major component of the lower food web, very little is known about the microbial makeup of this ecosystem. As a first step towards understanding the microbial and biogeochemical aspects of this system, a detailed molecular-based characterization of microbial communities, baseline chemistry, and physical characteristics of various springs of Ash Meadows will be …

The Role Of Rpoe In Stationary Phase Mutagenesis In Bacillus, Turquoise C. Alexander, Eduardo A. Robleto

Undergraduate Research Opportunities Program (UROP)

Stationary phase mutagenesis is a phenomenon whereby random mutations are generated in non-dividing cells. In order to understand how these mutations arise, we use Bacillus subtilis, a gram positive rod-shaped model organism. It is hypothesize that increased transcription promotes stationary phase mutagenesis in this organism. We therefore examined the role of rpoE, a gene that encodes RNA polymerase ! subunit and proposed to influence efficiency of transcription. To this end, we will first generate a strain bearing a deletion in the rpoE gene. In order to determine if this gene is important for mutagenesis, we will examine the accumulation of …

Germination And Characterization Of Bacillus Anthracis And Bacillus Cereus, Ann Desdemonia Nde-Neh Fowajuh, Ernesto Abel-Santos

Undergraduate Research Opportunities Program (UROP)

Bacillus cereus and Bacillus anthracis are micro organisms found in soil. Normally, only their spores are found in soil. We recently showed that, B. anthracis and B. cereus do not germinate in soil. Thus, how does B. cereus and B. anthracis continue their life cycle if they can not replicate in soil? We hypothesize that B. cereus and B. anthracis spores may germinate in the gut of nematodes. Caenorhabditis elegans was used as our model nematode to investigate this possibility. Subsequently, the goal of our research is to determine the effect of C. elegans on the life cycle of B. …