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Resistance To Dna Interstrand Crosslinks In Escherichia Coli Arises Through Prevention Rather Than Repair, Travis Kim Worley

Dissertations and Theses

DNA interstrand crosslinks are particularly lethal lesions that form in DNA when certain molecules intercalate between complementary strands of DNA and form covalent bonds with both strands. Once formed, these lesions present an absolute block to replication and transcription, ultimately resulting in cell death. Because of this lethality, chemicals that form DNA interstrand crosslinks are found in nature as defensive chemicals produced by plants and microbes. Moreover, crosslinking agents have proven effective the treatment of dysplastic conditions and are often first line chemotherapeutics.

However, cancer cells can become resistant to DNA interstrand crosslinks. Unlike other DNA lesions, the double-stranded nature …

Upland Cotton And Nematodes: An Analysis Of Historical Resistance, Upcoming Threats, And Co-Inoculation Effects, Amanda Gaudin

Theses and Dissertations

Upland cotton (Gossypium hirsutum ) is an important fiber crop grown throughout the southern United States. Plant-pathogenic nematodes are worm-like animals that feed on the roots of most agronomic crops, including cotton. The southern root-knot nematode (Meloidogyne incognita, RKN) and the reniform nematode (Rotylenchulus reniformis, RN) cause significant yield losses in cotton every year. Current sources of resistance are effective but limited, therefore historical screenings of cotton accessions were revisited in search for novel resistance sources. None were identified but many of the screened accessions possessed markers of known root-knot nematode and reniform nematode resistance. …

Precipitation And Soil Properties Determine Long-Term Consequences Of Disturbance And Invasion In Drylands, Tyson Terry

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Disturbance and invasive species have dramatic effects on desert plant communities, often resulting in degradation or shifts to alternative plant communities. Climate and soil properties determine water availability to plants, and have been thought to drive patterns of recovery following disturbance and potential for invasion.

In chapter II we used a combination of natural gas pipelines and satellite imagery to understand how recovery from a uniform disturbance differs across precipitation and soil gradients. We used a recovery ratio (disturbed/undisturbed) of pipeline pixels and their undisturbed nearest neighbor pixel to quantify recovery in a comparable way across precipitation gradients. We found …

Screening For Dmi And Mbc Fungicide Resistance In Monilinia Fructicola And Evaluation Of Biorational Products For Control Of Brown Rot On Peach In The Southeast United States, William Gura

All Theses

Monilinia fructicola (G. Winter) Honey is a fungal pathogen and is the causal agent of blossom blight, twig blight, green fruit rot, preharvest brown rot, and postharvest brown rot of peach (Prunus persica (L.) Batsch). Especially pre-and postharvest brown rot can have devastating economic impacts and negatively effects yield for peach growers throughout the southeastern United States. The most effective method for the control of pre- and postharvest brown rot is the application of synthetic fungicides during preharvest season. However, the consecutive use of fungicides with the same mode of action potentially give rise to resistance. This thesis focuses …

Study Of Population Dynamics Of Sugarcane Aphid (Melanaphis Sacchari) In Rio Grande Valley, Texas, Neetu Khanal

Theses and Dissertations

Chapter 1: This chapter incorporates detailed information about the biotype concept, aphids, their types and their biotypes, importance of studying insect biotypes and their role in mediating host plant defenses.

Chapter 2: This chapter explains in detail about the biology, biotypes, feeding behavior, damage, and economic loss caused due to sugarcane aphid infestation. This chapter further elaborates on the need for studying population level differences and justifies the objectives and significance of this research study.

Chapter 3: This chapter provides information about the comprehensive work done on three different populations of sugarcane aphid collected from three different locations in Rio …

Caribbean Reef-Building Coral-Symbiodiniaceae Network: Identifying Symbioses Critical For System Stability In A Changing Climate, Shaman Patel

All HCAS Student Capstones, Theses, and Dissertations

Increasing global ocean temperatures and frequency of marine heatwaves pose dire consequences for coral reefs. High temperatures often lead to disruptions in coral symbiosis resulting in coral bleaching, increasing the mortality of corals. However, corals can potentially avoid bleaching peril by associating with thermally tolerant symbionts. Here we provide a tool for understanding symbiosis network stability of Caribbean reef-building corals. We created a network of Caribbean hermatypic corals and their associated Symbiodiniaceae phylotypes. A bleaching model was applied to this network to test for resilience and robustness (R50) to thermal stress. It was also layered with trait data for coral …

Addressing Meloidogyne Enterolobii Spread In The Sweetpotato Industry: Development Of A High Throughput Survey Detection Method For Root-Knot Nematodes And Quantification Of M. Enterolobii Damage On Storage Roots In Long-Term Assays, Julianna Culbreath

All Theses

Meloidogyne enterolobii is an aggressive root-knot nematode (RKN) species that has emerged as a significant pathogen of sweetpotato in the Southeastern US. Meloidogyne enterolobii is spread through the movement of infected ‘seed’ sweetpotatoes used for propagation, and the RKN resistance in commercial sweetpotato cultivars has proven ineffective against this nematode. This has prompted regulatory agencies to impose quarantines on regions infected with M. enterolobii. Sweetpotato storage roots can be rendered unmarketable due to M. enterolobii infection, resulting in potential overall yield loss. Visual detection of RKN in sweetpotato can be unreliable, and further distinguishing M. enterolobii from other RKN species …

Esterase Mediated Insecticide Resistance In The Southern House Mosquito, Culex Quinquefasciatus, Vivek Pokhrel

LSU Doctoral Dissertations

Much is known about the development of insecticide resistance associated with targeted application against insect populations. However, off-target selection by applications of insecticides in agricultural and residential sites also impacts development of insecticide resistance and is understudied. Similarly, the impact of selecting one life stage of mosquitoes on the insecticide susceptibility of different life stages is largely unknown. The first part of this study shows that susceptibility to chlorantraniliprole, which is applied in rice and sugarcane fields in LA, decreased (5.7 to12-fold) in populations of Culex quinquefasciatus collected from near these fields compared to a reference field strain. In addition, …

Investigation Of Basil Downy Mildew Pathogen Survival, New Pathotype Development And Sources Of Quantitative, Kelly S. Allen

Doctoral Dissertations

Basil downy mildew (BDM) caused by the oomycete pathogen Peronospora belbahrii, threatens sweet basil (Ocimum basilicum) production worldwide. Chemical and cultural control options for BDM are limited, and resistant cultivars have only recently become available for commercial production. To address this challenging agricultural disease, this research investigates BDM epidemiology, occurrences of new pathotypes, and molecular plant-pathogen interactions leading to host resistance or susceptibility. A reproducible low-resource inoculation protocol was developed to harvest P. belbahrii inoculum and propagate BDM for further research. The survival of P. belbahrii sporangia was examined using an in vitro assay to assess germination …

Implications Of Antibiotic And Bacteriophage Resistance In Environmentally Isolated E. Coli, Michael Connolly

Honors Theses

The increasing prevalence of antibiotic-resistant bacteria is an emerging problem for humans. Clinical misuse, overuse in agricultural and food settings, and limited numbers of new antibiotics have accelerated the proliferation of antibiotic-resistant bacteria. To confront this threat, scientists must develop new therapeutics that kill these antibiotic-resistant bacteria. In this study, we used Escherichia coli to analyze antibiotic and bacteriophage susceptibility. E. coli is a common, mostly benign, enteric, gram-negative bacteria. We isolated three E. coli strains from the Hans Groot Kill, a stream that runs through Union College’s campus. We sought to assess various E. coli strains’ antibiotic resistance, susceptibility …

Plant Community Responses To Interactive Anthropogenic Disturbances Along A Natural-Wildland-Urban Gradient And Undergraduate Students’ Attitudes Toward Disturbances, Mali M. Hubert

Doctoral Dissertations

Anthropogenic disturbances are defined as any change caused by human activity that alters biodiversity. Wildfire and urbanization disturbances are among the most influential on the landscape because of their individual and interactive properties. Areas deemed wildland-urban interfaces (WUI; area where environment intermingles with human-built structures) are increasing near protected lands because of human population growth and movement, which often facilitates fire ignitions by humans. Houses that are adjacent to or overlap with wildland vegetation can complicate protection of urban development and wildlands from fires. The expansion of the WUI due to population growth will exacerbate fire risk, which can ultimately …

Evaluation Of Insecticide Resistance In Populations Of Tobacco Thrips, Frankliniella Fusca (Hinds), And Plant Density Effects On Thrips Injury To Cotton, Jessica L. Krob

Masters Theses

Two field studies were performed in Tennessee to evaluate the effects of plant density and seed spacing on thrips injury to upland cotton (Gossypium hirsutum L.). The plant density study consisted of seeding rate treatments that were low, normal, high, and very high, relative to university Extension recommendations. In the plant spacing study, treatments were implemented using nearly identical seeding rates but with relatively uniform seed spacing versus a clumped, “hill-dropped” spacing. In both studies, the seed was either treated with an insecticide (imidacloprid) and a fungicide or only with a fungicide. Due to variable environmental conditions, the results …

Marker-Trait Association Mapping Of Sorghum Mosaic Virus Resistance In Sugarcane, Chenie Zamora

LSU Master's Theses

Mosaic is a potentially devastating disease of sugarcane that had severe economic impact on Louisiana’s sugarcane industry in the 1920’s and has caused periodic problems ever since. The disease is vectored by migrating aphids that transmit Sugarcane mosaic virus (SCMV) and Sorghum mosaic virus (SrMV) in a non-persistent manner. Mosaic in Louisiana is currently caused by strains of SrMV. Mosaic has been controlled primarily by developing resistant cultivars. Recently, mosaic was detected in some near-commercial clones in the cultivar selection program. This prompted extensive screening of breeding program parent populations that detected infiltration of susceptibility and revealed the need for …

Antibacterial Activity Of Commiphora Molmol (Myrrha) Against The Periodontal Pathogen, Aggregatibacter Actinomycetemcomitans, Khalid Nafea Alharbi

Selected Full-Text Master Theses 2021-

The exogenous pathogen Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is most frequently involved in periodontitis and other systemic diseases. The treatment of these infections involves antibiotic therapy with Amoxicillin being the most popular antibiotic against A. actinomycetemcomitans but now, the drug is not 100% effective due to the development of 0-84% antibiotic resistance. The present study aimed to determine antibacterial activity of Commiphora molmol (Myrrha) against the periodontal pathogen, Aggregatibacter actinomycetemcomitans. In detail, the strain LIU1239 of Aggregatibacter actinomycetemcomitans was used where the plasmid pVJT128 is used for transposon mutagenesis and the Escherichia coli strain MV10Nal (stock # LIU4). The …

Coupled Structure-Function Responses To Disturbance: High Structural Complexity Resistance Supports Primary Production Resistance, Kerstin M. Niedermaier

Theses and Dissertations

The capacity of forests to resist structural change and retain material legacies–the biotic and abiotic resources that persist through disturbance–is crucial to sustaining ecosystem functioning after disturbance. However, the role of forest structure as both a material legacy and feature supporting carbon (C) cycling stability following disturbance has not been widely investigated. We used a large-scale disturbance manipulation to ask whether LiDAR-derived canopy structures as material legacies drive 3-year responses of NPP to a range of disturbance severity levels. As part of the Forest Resilience Threshold Experiment (FoRTE) in northern Michigan, USA we simulated phloem-disrupting disturbances at a range of …

Elucidating The Relationship Between Recombination Frequency And Antibiotic Resistance In Staphylococcus Aureus, Joseph R. Matthews

Legacy Theses & Dissertations (2009 - 2024)

Staphylococcus aureus is a common commensal and opportunistic pathogen of humans. It causes a variety of diseases, ranging from skin and soft infections to life-threatening invasive diseases. Many strains of S. aureus have developed resistance to a variety of antibiotic classes, including many beta-lactams. The evolution and dissemination of antibiotic resistance in S. aureus lay in large part to its remarkable ability of acquiring DNA from other organisms through horizontal gene transfer and recombination. In this study, I elucidated the relationship between frequencies of recombination events and horizontally acquired antibiotic resistant genes in a population of S. aureus sampled from …

Screening For Cry Proteins With Unique Receptors In Fall Armyworm (Spodoptera Frugiperda) And Corn Earworm (Helicoverpa Zea), Aria C. Deluna

Masters Theses

Bacillus thuringiensis (Bt) proteins have been the primary method for controlling Lepidopteran pests of corn and cotton over the past 20 years, due to their effectiveness and high level of target specificity. The fall armyworm (Spodoptera frugiperda) developed resistance to Cry1f, a Bt protein produced by both corn and cotton, within three years of registration in Puerto Rico. The evolution of resistance in pest insects poses as a threat to food safety as well as potentially resulting in economic losses of over $1 billion. The majority of Cry proteins follow a three domain (I to III) …

Genetic Resistance To The Downy Mildew Pathogen And Breeding Towards Durable Disease Management In Spinach, Bazgha Zia

Graduate Theses and Dissertations

Spinach (Spinacia oleracea) is a self-pollinated, dioecious winter crop. Prevalent challenges to the production of spinach include disease pressure imposed by downy mildew, which is caused by Peronospora effusa (=P. farinosa f. sp. spinaciae [Pfs]). A total of 19 new races of P. effusa have emerged, imposing serious challenges to the disease management in spinach production. Accordingly, this study was designed to explore the genetic components for establishing the basis of durable disease resistance development against the downy mildew pathogen (P. effusa 13) in spinach, through the use of various genome engineering approaches.

Our results have led (Chapter 2) to …

Evolution Of Targeted Therapy Resistance In Eml4-Alk Positive Non-Small Cell Lung Cancer, Robert Vander Velde

USF Tampa Graduate Theses and Dissertations

Targeted therapies have emerged as potent treatments that lead to the remission of many tumors. However, they rarely cure cancers in advanced, metastatic settings. This is due to the evolution of resistance, which in turn can be ascribed to the survival of small subpopulations of tolerant and/or resistant cells. Here we investigated the evolution of resistance to EML4-ALK inhibitors in non-small cell lung cancer (NSCLC) and demonstrated that resistance evolves gradually, from unique pre-treatment sub-populations, as multiple resistance mechanisms accumulate in a Darwinian fashion. Despite accumulating multiple changes, cells evolved, in parallel, toward similar inhibitor specific phenotypes. Evolving cells have …

Greater Sage-Grouse And Community Responses To Strategies To Mitigate Environmental Resistance In An Anthropogenic Altered Sagebrush Landscape, Justin R. Small

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Sagebrush (Artemisia spp.) ecosystems are diverse habitats found throughout western North America. Anthropogenic disturbances has resulted in the loss of over half of the sagebrush ecosystems impacting sagebrush obligate species such as sage-grouse (Centrocercus spp.). Federal, state, and private land managers have implemented landscape scale mechanical pinyon (Pinus spp.) and juniper (Juniperus spp.; conifer) removal projects in an effort to restore functioning sagebrush communities to benefit sage-grouse. However, few studies have investigated the potential for using large-scale conifer treatments to mitigate factors impeding sage-grouse seasonal movements and space-use in anthropogenic altered landscapes.

To address this management need, I …

Resistance To Aflatoxin Accumulation In Maize Mediated By Host-Induced Gene Silencing Of Aspergillus Flavus Alkaline Protease And O-Methyltransferase-A Genes, Olanike Omotola Omolehin

LSU Doctoral Dissertations

Aspergillus flavus is a soil-borne fungal pathogen that infects maize and produces aflatoxins. In the current study, portions of the alkaline protease (alk) and the O-methyl transferase (omtA) genes, which are key in A. flavus virulence and aflatoxin biosynthesis, respectively, were targeted for suppression through an RNAi (RNA interference) approach known as Host-Induced Gene Silencing (HIGS). Separate RNAi vectors were designed to carry regions of the alk and omtA gene fragments (Alk-RNAi and OmtA-RNAi) and introduced into B104 maize zygotic embryos. Eight and six transformation events were positive for the alk and omtA transgene, respectively. …

The Role Of Autophagy And Senescence In The Responses Of Non-Small Cell Lung Cancer Cells To Chemotherapy And Radiation, Nipa H. Patel

Theses and Dissertations

Cancer-associated deaths account for the second-highest mortality rates in the United States. Primary modalities of treatment often include surgery, radiation, and chemotherapy, and may also incorporate targeted therapy and immunotherapy. However, resistance to these treatments remains high, resulting in disease reoccurrence and poor survival rates. While apoptosis or cell death of tumor cells is the ideal outcome for anti-cancer therapy, this is often not the case, and in fact cancer cells may upregulate several pathways, such as autophagy and senescence, as a means to undergo alternative cell fate and evade apoptotic cell death. An essential tumor suppressor gene, TP53, …

A Genetic Investigation Of Anticoagulant Rodenticide Resistance In Mus Musculus Of Western Australia: Implications For Conservation And Biosecurity, Bridget Judith Maria Lucrezia Duncan

Theses : Honours

Human-wildlife interactions have developed since the agricultural revolution that occurred 10,000 years ago, and the expansion of commensal species’ geographical distribution led to conflicts that prompted humans to adopt a wide range of control methods for pest species (Horvitz, Wang, Wan, & Nathan, 2017; Riyahi et al., 2013; Saraswat, Sinha, & Radhakrishna, 2015). The order Rodentia is characterised by a high number of successful invaders, which humans have attempted to manage with the use of anticoagulant rodenticides (ARs) since the 1940s (Capizzi, Bertolino, & Mortelliti, 2014; Ruiz-Suárez et al., 2014). The rise and spread of a genetic mutation that infers …

Incidence Of Antibiotic Resistance And Plasmid Content In Freshwater Beach Sand And Water And Clinical Urinary Tract Infection Escherichia Coli Isolates, Robert F. White

Biology Theses

Antibiotic-resistant (AR) bacteria have been found in environmental ecosystems including beach sand and water, and pose a serious threat to the mitigation of human and animal disease. The presence of antibiotic residues in the environment, fueled by wastewater effluent and agricultural runoff, may produce selective pressure on introduced microbes such as Escherichia coli, leading to the production of AR populations. This study characterized and compared the antibiotic resistance patterns and plasmid content of E. coli isolated from a freshwater beach and clinical urinary tract infection (UTI) samples. A higher level of antibiotic resistance was expected in clinical (UTI) Escherichia coli …

Insecticide Resistance Management Approaches And Naturally Derived Toxicants For The Control Of Fall Armyworm, Spodoptera Frugiperda, Sarah Mccomic

LSU Master's Theses

Spodoptera frugiperda, the fall armyworm (FAW), is a major agricultural pest causing billions of dollars in damage annually to staple crops. Agricultural losses stemming from this pest continues to increase as resistance to commercialized insecticide classes evolves and spreads. Considering this, novel chemistries with new modes of action as well as novel resistance management strategies need to be developed to achieve continued control of FAW populations. This project consisted of two main goals. First, we aimed to develop a neurophysiological assay to enable a more precise understanding of pyrethroid and organophosphate resistance at the level of the nerve. We …

Helicoverpa Zea (Boddie) (Lepidoptera: Noctuidae) Larval Distribution On Different Bt Technologies And Evaluating Cotton Plant Tissue Assays For Resistance Monitoring, Dawson David Kerns

Masters Theses

Field trials were conducted in 2018 at the West Tennessee Research and Education Center (WTREC) in Jackson, TN and in 2019 at locations in College Station, TX, Tillar, AR, and Jackson, TN. Non-Bt, Cry1Ac + Cry1F, and Cry1Ac + Cry2Ab cotton varieties were either treated with an insecticide or left untreated. After five days, cotton plants were mapped for signs of bollworm, Helicoverpa zea (Lepidoptera: Noctuidae), feeding on floral structures (i.e., bolls, squares, flowers) and the physical presence of larvae. Bt technologies reduced the number of H. zea larvae and the amount of feeding injury, but no major differences in …

Public Relations Of Cal Poly Avocado Rootstock Trial, Angel Daniel Carrillo

Agricultural Education and Communication

Avocados have been one of California’s specialty crops for quite some time now. The industry has been motivating growers to implement the best management practices to ensure stable and increased production as much as they possibly can. California is the leading state in the country for avocado production. In 2019, California alone produced 109 tons of avocados (US Department of Agriculture, 2020). Unfortunately, root rot has made it a challenge to do so.

Root rot is a disease derived from the Phytophthora cinnamomi pathogen. This is an issue for avocado production worldwide. In efforts to find a method of decreasing …

Use Of Acetolactate Synthase-Inhibiting Herbicides In Inzen Grain Sorghum (Sorghum Bicolor L. Moench Ssp. Bicolor), Hunter Bowman

Graduate Theses and Dissertations

Grain sorghum is typically grown as a rotational crop in Arkansas because of its many benefits, one being the effective control of Palmer amaranth through the use of atrazine. However, limited options exist for postemergence (POST) control of weedy grasses within the crop. Inzen™ grain sorghum is the result of a nicosulfuron resistant weedy sorghum biotype cross-bred with a commercial line of grain sorghum. Inzen™ allows for safe use of over-the-top applications of nicosulfuron within the crop. Nicosulfuron is an acetolactate synthase (ALS)-inhibiting herbicide, which has historically been used in corn for control of weedy grasses. Experiments were conducted in …

Mapping Quantitative Trait Loci For Peach (Prunus Persica) Resistance To Xanthomonas Arboricola Pv. Pruni (Xap) And Determining The Diversity And Virulence Of A United States Xap Collection, Maxwell Vonkreuzhof

Graduate Theses and Dissertations

Bacterial spot, caused by the bacterium Xanthomonas arboricola pv. pruni (Xap), is a threat to the peach [Prunus persica (L.) Batsch], Japanese and European plum (P. salicina L. and P. domestica L.), and tart and sweet cherry (P. cerasus L. and P. avium L.) industries. Markers for fruit resistance to bacterial spot have been developed however, markers associated with foliar resistance have yet to be developed. A total of 130 progeny and 13 parents (n=143) were evaluated for foliar and fruit Xap resistance in 2013, 2014, and 2015, and 162 progeny and eight parents (n=170) in 2017 and 2018 as …

Exploring Putative Herbicide Resistance In Two Summer Annual Grassy Weeds, Benjamin D. Pritchard

Chancellor’s Honors Program Projects

No abstract provided.