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 Department: Department of Biology
 Collection: UNT Theses and Dissertations
Changes in Gene Expression Levels of the Ecf Sigma Factor Bov1605 Under Ph Shift and Oxidative Stress in the Sheep Pathogen Brucella Ovis

Changes in Gene Expression Levels of the Ecf Sigma Factor Bov1605 Under Ph Shift and Oxidative Stress in the Sheep Pathogen Brucella Ovis

Date: December 2012
Creator: Kiehler, Brittany Elaine
Description: Brucella ovis is a sexually transmitted, facultatively anaerobic, intracellular bacterial pathogen of sheep (Ovis aries) and red deer (Cervus elaphus). Brucella spp. infect primarily by penetrating the mucosa and are phagocytized by host macrophages, where survival and replication occurs. At least in some species, it has been shown that entry into stationary phase is necessary for successful infection. Brucella, like other alphaproteobacteria, lack the canonical stationary phase sigma factor ?s. Research on diverse members of this large phylogenetic group indicate the widespread presence of a conserved four-gene set including an alternative ECF sigma factor, an anti-sigma factor, a response regulator (RR), and a histidine kinase (HK). The first description of the system was made in Methylobacterium extorquens where the RR, named PhyR, was found to regulate the sigma factor activity by sequestering the anti-sigma factor in a process termed "sigma factor mimicry." These systems have been associated with various types of extracellular stress responses in a number of environmental bacteria. I hypothesized that homologous genetic sequences (Bov_1604-1607), which are similarly found among all Brucella species, may regulate survival functions during pathogenesis. To further explore the involvement of this system to conditions analogous to those occurring during infection, pure cultures of ...
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Detection of Mercury Among Avian Trophic Levels at Caddo Lake and Lake Lewisville, TX

Detection of Mercury Among Avian Trophic Levels at Caddo Lake and Lake Lewisville, TX

Date: May 2012
Creator: Schulwitz, Sarah Elizabeth
Description: Mercury (Hg) is a globally distributed toxicant that has been shown to have negative effects on birds. in the United States, avian taxa have been shown to possess high Hg concentrations in the northeast, Great Lakes and Everglades ecosystems; however, few studies have measured avian Hg concentrations in other geographic regions. Previous studies have documented high Hg concentrations in multiple organisms in east Texas, but birds were not included in these studies. the main objective of the present study was to quantify Hg concentrations in birds in differing trophic levels at Caddo Lake and Lake Lewisville, TX. Results suggest that Hg concentrations may be high enough to negatively impact some bird taxa, particularly those at high trophic levels, residing at both Caddo Lake and Lake Lewisville.
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Examining the Shade/flood Tolerance Tradeoff Hypothesis in Bottomland Herbs Through Field Study and Experimentation

Examining the Shade/flood Tolerance Tradeoff Hypothesis in Bottomland Herbs Through Field Study and Experimentation

Date: May 2012
Creator: Sloop, Jordan
Description: While there is growing evidence that shade/flood tolerance tradeoffs may be important in distributions of bottomland hardwood trees and indications that they should apply to herbs, no studies have definitively explored this possibility. Four years of field data following historic flooding were supplemented with a greenhouse experiment designed to identify interactions congruent with tradeoffs. Fifteen bottomland species were grown in two levels of water availability and three levels of shade over 10 weeks. Results indicate responses of Fimbristylis vahlii and Ammannia robusta are consistent with tradeoffs. Modification of classical allometric responses to shade by substrate saturation indicates a potential mechanism for the tradeoff in A. robusta. Responses indicating potential for increased susceptibility to physical flooding disturbance are also discussed.
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A geospatial tool for assessing potential wildland fire risk in central Texas.

A geospatial tool for assessing potential wildland fire risk in central Texas.

Date: August 2005
Creator: Hunter, Bruce Allan
Description: Wildland fires in the United States are not always confined to wilderness areas. The growth of population centers and housing developments in wilderness areas has blurred the boundaries between rural and urban. This merger of human development and natural landscape is known in the wildland fire community as the wildland urban interface or WUI, and it is within this interface that many wildland fires increasingly occur. As wildland fire intrusions in the WUI increase so too does the need for tools to assess potential impact to valuable assets contained within the interface. This study presents a methodology that combines real-time weather data, a wildland fire behavior model, satellite remote sensing and geospatial data in a geographic information system to assess potential risk to human developments and natural resources within the Austin metropolitan area and surrounding ten counties of central, Texas. The methodology uses readily available digital databases and satellite images within Texas, in combination with an industry standard fire behavior model to assist emergency and natural resource managers assess potential impacts from wildland fire. Results of the study will promote prevention of WUI fire disasters, facilitate watershed and habitat protection, and help direct efforts in post wildland fire mitigation and ...
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Construction of a  Pseudomonas aeruginosa Dihydroorotase Mutant and the Discovery of a Novel Link between Pyrimidine Biosynthetic Intermediates and the Ability to Produce Virulence Factors

Construction of a Pseudomonas aeruginosa Dihydroorotase Mutant and the Discovery of a Novel Link between Pyrimidine Biosynthetic Intermediates and the Ability to Produce Virulence Factors

Date: August 2003
Creator: Brichta, Dayna Michelle
Description: The ability to synthesize pyrimidine nucleotides is essential for most organisms. Pyrimidines are required for RNA and DNA synthesis, as well as cell wall synthesis and the metabolism of certain carbohydrates. Recent findings, however, indicate that the pyrimidine biosynthetic pathway and its intermediates maybe more important for bacterial metabolism than originally thought. Maksimova et al., 1994, reported that a P. putida M, pyrimidine auxotroph in the third step of the pathway, dihydroorotase (DHOase), failed to produce the siderophore pyoverdin. We created a PAO1 DHOase pyrimidine auxotroph to determine if this was also true for P. aeruginosa. Creation of this mutant was a two-step process, as P. aeruginosa has two pyrC genes (pyrC and pyrC2), both of which encode active DHOase enzymes. The pyrC gene was inactivated by gene replacement with a truncated form of the gene. Next, the pyrC2 gene was insertionally inactivated with the aacC1 gentamicin resistance gene, isolated from pCGMW. The resulting pyrimidine auxotroph produced significantly less pyoverdin than did the wild type. In addition, the mutant produced 40% less of the phenazine antibiotic, pyocyanin, than did the wild type. As both of these compounds have been reported to be vital to the virulence response of P. aeruginosa, ...
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Integrating Concepts in Modern Molecular Biology into a High School Biology Curriculum

Integrating Concepts in Modern Molecular Biology into a High School Biology Curriculum

Access: Use of this item is restricted to the UNT Community.
Date: August 2003
Creator: Parker, Timothy P.
Description: More so than any other science in the past several decades, Biology has seen an explosion of new information and monumental discoveries that have had a profound impact on much more than the science itself. Much of this has occurred at the molecular level. Many of these modern concepts, ideas, and technologies, as well as their historical context, can be easily understood and appreciated at the high school level. Moreover, it is argued here that the integration of this is critical for making biology relevant as a modern science. A contemporary high school biology curriculum should adequately reflect this newly acquired knowledge and how it has already has already begun to revolutionize medicine, agriculture, and the study of biology itself. This curriculum provides teachers with a detailed framework for integrating molecular biology into a high school biology curriculum. It is not intended to represent the curriculum for an entire academic year, but should be considered a significant component. In addition to examining key concepts and discoveries, it examines modern molecular techniques, their applications, and their relevance to science and beyond. It also provides several recommended labs and helpful protocols.
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Laboratory and field studies of cadmium effects on  Hyalella azteca in effluent dominated systems.

Laboratory and field studies of cadmium effects on Hyalella azteca in effluent dominated systems.

Date: August 2003
Creator: Stanley, Jacob K.
Description: Laboratory single-species toxicity tests are used to assess the effects of contaminants on aquatic biota. Questions remain as to how accurately these controlled toxicity tests predict sitespecific bioavailability and effects of metals. Concurrent 42-day Hyalella azteca exposures were performed with cadmium and final treated municipal effluent in the laboratory and at the University of North Texas Stream Research Facility. Further laboratory testing in reconstituted hard water was also conducted. Endpoints evaluated include survival, growth, reproduction, and Cd body burden. My results demonstrate that laboratory toxicity tests may overestimate toxicity responses to cadmium when compared to effluent dominated stream exposures. Discrepancies between endpoints in the three tests likely resulted from increased food sources and decreased cadmium bioavailability in stream mesocosms
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Investigation of Pyrimidine Salvage Pathways to Categorize Indigenous Soil Bacteria of Agricultural and Medical Importance and Analysis of the Pyrimidine Biosynthetic Pathway's Enzyme Properties for Correlating Cell Morphology to Function in All Phases of Growth

Investigation of Pyrimidine Salvage Pathways to Categorize Indigenous Soil Bacteria of Agricultural and Medical Importance and Analysis of the Pyrimidine Biosynthetic Pathway's Enzyme Properties for Correlating Cell Morphology to Function in All Phases of Growth

Date: May 2003
Creator: Meixner, Jeffery Andrew
Description: This dissertation comprises three parts and is presented in two chapters. Chapter 1 concerns Arthrobacter, a bacterium with an intriguing growth cycle. Whereas most bacteria exist as either a rod or coccus, this bacterium shares the rod/coccus lifestyle. It therefore seemed important to examine the growth regulatory pathways from the rod and coccus. The committed step, that catalyzed by aspartate transcarbamoylase (ATCase), in the pyrimidine biosynthetic pathway was chosen. The ATCase in Arthrobacter is like the well known Pseudomonas enzyme except that it has an active dihydroorotase (DHOase) associated. Included in Chapter 1 is the description of a microorganism, Burkholderia cepacia, whose ATCase has characteristics that are at once reminiscent of bacteria, mammals, and fungi. It differs in size or aggregation based on environmental conditions. In addition, it has an active DHOase associated with the ATCase, like Arthrobacter. B. cepacia is important both medically and for bioremediation. Since B. cepacia is resistant to most antibiotics, its unique ATCase is a prime target for inhibition. Whereas the first chapter deals with the de novo pathway to making pyrimidines, which is found mainly in the lag and log phase, Chapter 2 addresses the salvage pathway, which comes more into play during the ...
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On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

Access: Use of this item is restricted to the UNT Community.
Date: May 2003
Creator: Dohanich, Francis Albert
Description: On-road remote sensing has the ability to operate in real-time, and under real world conditions, making it an ideal candidate for detecting gross polluters on major freeways and thoroughfares. In this study, remote sensing was employed to detect carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NO). On-road remote sensing data taken from measurements performed in six states, (Arizona, California, Colorado, Illinois, Texas, and Utah) were cleaned and analyzed. Data mining and exploration were first undertaken in order to search for relationships among variables such as make, year, engine type, vehicle weight, and location. Descriptive statistics were obtained for the three pollutants of interest. The data were found to have non-normal distributions. Applied transformations were ineffective, and nonparametric tests were applied. Due to the extremely large sample size of the dataset (508,617 records), nonparametric tests resulted in "p" values that demonstrated "significance." The general linear model was selected due to its ability to handle data with non-normal distributions. The general linear model was run on each pollutant with output producing descriptive statistics, profile plots, between-subjects effects, and estimated marginal means. Due to insufficient data within certain cells, results were not obtained for gross vehicle weight and engine type. The "year" ...
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Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Date: December 2002
Creator: Brooks, Bryan W.
Description: The University of North Texas Stream Research Facility (UNTSRF) was designed to examine contaminant impacts on effluent-dominated stream ecosystems. Stream mesocosms, fed municipal effluent from the City of Denton, TX, Pecan Creek Water Reclamation Plant (PCWRP), were treated with 0, 15 or 140 µg/L cadmium for a 10-day study in August 2000. Laboratory toxicity test and stream macroinvertebrate responses indicated that cadmium bioavailability was reduced by constituents of effluent-dominated streams. The Biotic Ligand Model (BLM) for Cd was used to predict a 48 hour Cd EC50 for Ceriodaphnia dubia of 280 µg/L in these effluent-dominated streams. This value is higher that an EC50 of 38.3 µg/L Cd and a 7-day reproduction effect level of 3.3 µg/L Cd generated for C. dubia in reconstituted laboratory hard water. These results support use of a cadmium BLM for establishing site-specific acute water quality criteria in effluent-dominated streams. Although not affected by 15 µg/L treatments, organisms accumulated Cd in 15 µg/L treated streams. Hence, over longer exposure periods, Cd accumulation may increase and a no effect level may be lower than the observed 10-day no effect level of 15 µg/L. A toxicity identification evaluation procedure was utilized with in vitro and in vivo bioassays ...
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