Life Sciences Commons^™

Exploring The Interactions Between Sars-Cov-2 And Host Proteins., Sojan Shrestha

School of Biological Sciences: Dissertations, Theses, and Student Research

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the current pandemic, Coronavirus Disease 2019 (COVID-19). SARS-CoV-2 is considered to be of zoonotic origin; it originated in non-human animals and was transmitted to humans. Since the early stage of the pandemic, however, the evidence of transmissions from humans to animals (reverse zoonoses) has been found in multiple animal species including mink, white-tailed deer, and pet and zoo animals. Furthermore, secondary zoonotic events of SARS-CoV-2, transmissions from animals to humans, have been also reported. It is suggested that non-human hosts can act as SARS-CoV-2 reservoirs where accumulated …

Evaluating Assessment Score Validity And Characterizing Undergraduate Biology Exam Content, Crystal Uminski

School of Biological Sciences: Dissertations, Theses, and Student Research

The landscape of undergraduate biology education has been shaped by decades of reform efforts calling for instruction to integrate core concepts and scientific skills as a means of helping students become proficient in the discipline. Assessments can be used to make inferences about how these reform efforts have translated into changes in department curriculum and course practices. Such changes can be measured using student scores on researcher-developed programmatic and concept assessments. Scores on these assessments are often assumed to be accurate representations of student biology content knowledge, but my work indicates that the validity of these interpretations may be threatened …

Mitochondrial Functions Are Major Targets Of Isocyanide Activity In Saccharomyces Cerevisiae, Morgan A. Siemek

School of Biological Sciences: Dissertations, Theses, and Student Research

The isocyanide functional group is important in the synthesis of many organic compounds and is found in natural products produced by plants, bacteria, marine invertebrates, and fungi. The antimicrobial activities of isocyanide compounds have been documented for almost 70 years, however, the biochemical targets and mechanisms of action remain poorly defined. We report antimicrobial activity of 4-para-nitrophenyl-isocyanide (p-NPIC) against a model fungus, Saccharomyces cerevisiae, and the human fungal pathogen Candida albicans. To identify the cellular and molecular targets of p-NPIC, we screened the non-essential single gene-deletion collection of S. cerevisiae. We aimed …

A Tale Of Two Genomes: The Complex Interplay Between The Mitochondrial And The Nuclear Genomes, Abhilesh S. Dhawanjewar

School of Biological Sciences: Dissertations, Theses, and Student Research

Mitochondria, the product of an ancient endosymbiotic event are pivotal to eukaryotic cells by synthesizing the majority of the cell’s ATP output. However, modern- day mitochondria are completely dependent on more than one thousand nuclear-encoded products for their function and the maintenance of their genomes. The fundamentally different ways in which the mitochondrial (mtDNA) and the nuclear (nucDNA) genomes are replicated and inherited lead to captivating coevolutionary dynamics between them. The aims of this dissertation are to investigate the coevolutionary dynamics between the mitochondrial and nuclear genomes at three distinct biological scales. At the organismal level, we use a Drosophila …

Discovering Novel Polyextremotolerant Fungi, And Determining Their Ecological Role Within The Biological Soil Crust Consortium, Erin Carr

School of Biological Sciences: Dissertations, Theses, and Student Research

The ecological niche of polyextremotolerant fungi within oligotrophic ecosystems such as biological soil crusts has not yet been determined. These fungi persist in locations where nutrients are depleted while simultaneously surrounded by autotrophic microbes such as algae and cyanobacteria. Yet it has not been shown that they are engaging in any exchange of nutrients the way lichens do. However, there is seemingly no other way for these fungi to obtain vital nutrients, such as carbon or nitrogen, other than from these microbes. Here we have isolated polyextremotolerant fungi from cold desert biological soil crusts which are a microbial biofilm that …

Transcriptome Assembly And Characterization Of Chemoreceptors For Corn Rootworms, Bailee Egan

School of Biological Sciences: Dissertations, Theses, and Student Research

The western corn rootworm (Diabrotica virgifera virgifera LeConte) is the most important insect pest of corn in the United States Corn Belt, costing the agricultural industry over two billion dollars per year. As current management practices have been losing their effectiveness, new targets for corn rootworm control need to be explored. In this thesis, we focused on identifying rootworm chemoreceptors, which can be considered for potential targets for management. Transcriptomes from seven life stages were assembled for the western corn rootworm as well as two other related corn rootworm species, the northern corn rootworm (D. barberi) and …

Methanogen Metabolic Flexibility, Sean Carr

School of Biological Sciences: Dissertations, Theses, and Student Research

Methanogens are obligately anaerobic archaea which produce methane as a byproduct of their respiration. They are found across a wide diversity of environments and play an important role in cycling carbon in anaerobic spaces and the removal of harmful fermentation byproducts which would otherwise inhibit other organisms. Methanogens subsist on low-energy substrates which requires them to utilize a highly efficient central metabolism which greatly favors respiratory byproducts over biomass. This metabolic strategy creates high substrate:product conversion ratios which is industrially relevant for the production of biomethane, but may also allow for the production of value-added commodities. Particularly of interest are …

Access To Online Formative Assessments In Introductory Biology Courses: Investigating Barriers To Student Engagement, Allison Upchurch

School of Biological Sciences: Dissertations, Theses, and Student Research

Instructors use a variety of online formative assessment (FA) activities to support learning outside of class. Previous studies have revealed barriers for students in online courses, but little is known about the barriers students experience when completing online FA assignments. Understanding these barriers to access is critical to fostering more inclusive learning for all students. Using a framework from previous work in online learning, we examined student perceptions of online FA access with respect to five barrier categories: technical resources, instructor organization, social interactions, personal engagement, and learning environment. We developed and administered a survey to over 1200 undergraduate biology …

Mitochondrial Genome Structure And Double Strand Break Repair In Arabidopsis Thaliana, Sterling Ericsson

School of Biological Sciences: Dissertations, Theses, and Student Research

The mitochondrial genomes of plants are known for their variability in size and arrangement, yet low mutation rates in coding sequences. These opposing characteristics have been suggested to be due to the stability of their DNA maintenance processes and the usage of a double strand break repair (DSBR) system. The components of this repair complex remain poorly understood and only a few of the involved enzymes have been identified, making direct analysis difficult. The flowering plant species Arabidopsis thaliana has been used as a model organism for genome modification and subsequent phenotypic and genotypic impacts. The aims of this research …

Studies Of The Dutpase Of The Western Corn Rootworm, Carlos Riera-Ruiz

School of Biological Sciences: Dissertations, Theses, and Student Research

The western corn rootworm (WCR), Diabrotica virgifera virgifera, is a major corn pest in the United States and Europe. WCR has developed resistance to multiple management strategies, including Cry proteins. Even though the biology and ecology have been thoroughly studied in WCR, their genome and molecular mechanisms are understudied. This work focuses on the ubiquitous enzyme deoxyuridine triphosphatase (dUTPase) encoded by the DUT gene. dUTPase hydrolyzes dUTP into dUMP and pyrophosphate. It contributes to genome stability by keeping the uracil-to-thymine ratio at a certain level. In WCR, two dUTPase isoforms were predicted using transcriptome analyses. These two potential isoforms …

Characterization Of A Novel Glycerol-3-Phosphate Dehydrogenase (Gpd2) In The Alga Chlamydomonas Reinhardtii, Itzela A. Cruz Powell

School of Biological Sciences: Dissertations, Theses, and Student Research

The green alga Chlamydomonas reinhardtii, like many eukaryotic microalgae, accumulates triacylglycerol (TAG) under certain environmental stresses, such as nitrogen deprivation. TAG is of interest because it is an essential precursor for biofuel production. Canonical glycerol-3-phosphate dehydrogenases catalyze the synthesis of glycerol-3-phosphate (G3P), a key precursor for glycerolipid and TAG synthesis in eukaryotes. The C. reinhardtii genome encodes six GPD homologs. Interestingly, GPD2 is a novel multidomain enzyme, consisting of a phosphatase motif fused to a G3P dehydrogenase domain. GPD2 expression is significantly up-regulated under nutrient deprivation or high salinity, coincidental with the accumulation of TAG or glycerol. Conversely, RNA-mediated …

Characterization Of Novel Chlorovirus Glycosyltransferases That Synthesize Atypical Glycans, Eric Noel

School of Biological Sciences: Dissertations, Theses, and Student Research

Giant dsDNA chloroviruses encode a diverse repertoire of glycosyltransferases (GTases) and methyltransferases (MTases) that biosynthesize unusual, methylated sugars independent of their host chlorella-like green algae prompting a reexamination of glycobiology systems. Unlike most other viruses, the prototype chlorovirus PBCV-1 encodes most, if not all, of the machinery required to glycosylate its major capsid protein (MCP). The structures of the four N-linked glycans do not resemble any other glycans in the three domains of life. Here, we investigated the potential involvement of chlorovirus- encoded putative GTases and MTases in glycosylation of the viral MCP. First, we aimed to generate site-directed …

Polerovirus Genomic Variation And Mechanisms Of Silencing Suppression By P0 Protein, Natalie Holste

School of Biological Sciences: Dissertations, Theses, and Student Research

The family Luteoviridae consists of three genera: Luteovirus, Enamovirus, and Polerovirus. The genus Polerovirus contains 32 virus species. All are transmitted by aphids and can infect a wide variety of crops from cereals and wheat to cucurbits and peppers. However, little is known about how this wide range of hosts and vectors developed. In poleroviruses, aphid transmission and virion formation is mediated by the coat protein read-through domain (CPRT) while silencing suppression and phloem limitation is mediated by Protein 0 (P0)—a protein unique to poleroviruses. P0 gives poleroviruses a great advantage amongst plant viruses and diversifies polerovirus species, but the …

Metagenomic, Viral And Host Genetic Analyses Of Congenital Tremor In Pigs, Kylee Sutton

School of Biological Sciences: Dissertations, Theses, and Student Research

The Pestivirus genus contains several viral species having a major impact on the livestock species. While there were only four major pestiviral species for a time, recent metagenomic sequencing approaches identified additional species, such as atypical porcine pestivirus (APPV). Congenital tremor was first identified almost a hundred years ago and since still has an impact on swine health. There are two main types of congenital tremor, type A and B, with type A congenital tremor further subcategorized based on causative agent. Until recently, type A-II congenital tremor did not have a known cause. Recent viral sequencing of affected samples, including …

Bioinformatic Analysis Of The Gut Microbiota Derived From The Oil Fly Helaeomyia Petrolei From The La Brea Tar Pits, Brian Dillard

School of Biological Sciences: Dissertations, Theses, and Student Research

In the early 1930s, Thorpe a prominent entomologist, called for more research into Helaeomyia petrolei larva. These larvae live in the Californian La Brea tar pits where they are exposed to large amounts of polyaromatic hydrocarbons. Molecules like anthracene, phenanthrene, and toluene which should be highly toxic to both the oil fly larvae and its enteric bacteria. This extremophilic gut microbiome has yet to be studied using current day next gen sequencing and bioinformatic techniques. In fact, since Thorpe’s work in the 1930s, there have been only two publications characterizing the oil fly larvae. Both in the early 2000s by …

Prey Selection By Birds Of Prey, Anisha Pokharel

School of Biological Sciences: Dissertations, Theses, and Student Research

Prey selection is key to determine predator prey interaction and understanding the complexity of food web structure. In this thesis, we used two different approaches to understanding prey selection by North American birds of prey. Using a conventional method, in Chapter 1 we compared pellet analysis and trapping data to assess patterns of prey selection of barn owls in western Nebraska. Microtus spp. comprised 55.8% of the prey items in the barn owl’s diet. The proportion of several prey types in the diet were significantly different from the expected proportion based on trapping. This pattern may indicate barn owls actively …

The Relationship Between The Cervical Microbiome And Cervical Cancer Risk In Sub-Saharan Africa, Cameron Klein

School of Biological Sciences: Dissertations, Theses, and Student Research

Despite ongoing efforts, sub-Saharan Africa faces a higher cervical cancer burden than anywhere else in the world. Besides HPV infection, definitive factors of cervical cancer are still unclear. Dysbiosis of the cervicovaginal microbiota, particularly involving sexually transmitted infections, is associated with increased cervical cancer risk. Notably, HIV infection, which is prevalent in sub-Saharan Africa, greatly increases risk of cervicovaginal dysbiosis and cervical cancer. To better understand and address cervical cancer in sub-Saharan Africa, a better understanding of the regional cervicovaginal microbiome is required. In this study, I establish the relationship between cervical cancer, HPV, HIV, cervicovaginal infections, and the cervicovaginal …

Functions Of Vocal Mimicry In The Complex Song Of The European Starling, Sturnus Vulgaris, Maria Goller

School of Biological Sciences: Dissertations, Theses, and Student Research

Vocal learning is an ability that has only evolved in a handful of taxa. Songbirds learn their songs, and some species have flexible learning in which they not only incorporate species-specific sounds, but heterospecific and/or environmental sounds as well. The functions of vocal mimicry are still unknown for many species and studying mimicry can teach us about the variation within the song learning process. In this thesis, I focused on five hypotheses on how mimicry could function in sexual selection. The repertoire size hypothesis suggests that selection for larger repertoire sizes allows mimicry to occur because imitation can increase repertoire …

Dgts Production As A Phosphate Starvation Response In The Human Fungal Pathogen Candida Albicans, Caleb Wehling

School of Biological Sciences: Dissertations, Theses, and Student Research

Betaine lipids are a class of membrane lipids with betaine head groups. Three betaine lipids are known - diacylglyceryltrimethylhomoserine (DGTS), diacylglycerylhydroxymethylalanine (DGTA), and diacylglycerylcarboxymethylcholine (DGCC). Betaine lipids are most common in algae, although DGTS, the most common betaine lipid, is also found in many bacteria and fungi. Organisms which produce betaine lipids (especially DGTS) often don’t produce phosphatidylcholine (PtdCho), and DGTS structure resembles PtdCho structure without any phosphorous, leading to the hypothesis that betaine lipids may substitute for phospholipids in some organisms. This has been confirmed by discoveries that some organisms are capable of switching their membrane composition from PtdCho …

Identification Of The Kaposi's Sarcoma-Associated Herpesvirus (Kshv) Surface Glycoprotein Targets Of Human Kshv-Specific Neutralizing Antibody Responses, Yasaman Mortazavi

School of Biological Sciences: Dissertations, Theses, and Student Research

Kaposi’s sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8), is the etiological agent of Kaposi’s sarcoma (KS), and is also associated with two B cell malignancies, primary effusion lymphoma and multicentric Castleman's disease. The distribution of KSHV varies globally with high prevalence in some areas of sub-Saharan Africa (SSA), where seroprevalence can be as high as 80%. It is estimated that nearly 44,000 new cases of KS emerge annually globally, with the highest incidents occurring in Africa, where KSHV is endemic. Currently, there is no prophylactic vaccine against KSHV, and efforts to develop prophylactic vaccines have been limited. …

Plant Mitochondrial Genome Evolution And Structure Has Been Shaped By Double-Strand Break Repair And Recombination, Emily Wynn

School of Biological Sciences: Dissertations, Theses, and Student Research

Plant mitochondrial genomes are large but contain a small number of genes. These genes have very low mutation rates, but genomes rearrange and expand at significant rates. We propose that much of the apparent complexity of plant mitochondrial genomes can be explained by the interactions of double-strand break repair, recombination, and selection. One possible explanation for the disparity between the low mutation rates of genes and the high divergence of non-genes is that synonymous mutations in genes are not truly neutral. In some species, rps14 has been duplicated in the nucleus, allowing the mitochondrial copy to become a pseudogene. By …

Regulation Of Vaccinia Virus Replication: A Story Of Viral Mimicry And A Novel Antagonistic Relationship Between Vaccinia Kinase And Pseudokinase, Annabel T. Olson

School of Biological Sciences: Dissertations, Theses, and Student Research

Poxviruses employ sophisticated signaling pathways that thwart cellular defense mechanisms and simultaneously ensure viral factors are modulated properly. Yet, our understanding of these complex signaling networks are incomplete. For example, the vaccinia B1 kinase plays a vital role in inactivating the cellular antiviral factor BAF, and is suggested to orchestrate other pathways. B1 is highly conserved among poxviruses and exhibits a remarkable degree of similarity to VRKs, a family of cellular kinases, suggesting that the viral enzyme has evolved to mimic VRK activity. Indeed, B1 and VRKs have been demonstrated to target a shared substrate, the DNA binding protein BAF, …

Establishing Benchmark Criteria For Single Chromosome Bacterial Genome Assembly, Timothy Krause

School of Biological Sciences: Dissertations, Theses, and Student Research

Adequate recommendations for the amount and types of sequencing data necessary to optimize the recovery of single chromosomes from bacterial sequencing projects do not exist. Broad estimates for coverage depths needed to recover complete bacterial genomes are present in the literature, but required sequencing depths across bacterial and archaeal phylogenies needed for high-quality assembly are not known. Additionally, correlations between genomic complexity and expected quality of assembly have not been properly defined. Furthermore, the capabilities of multiplexing (sequencing more than one sample simultaneously on one flow cell) with long-read sequencing platforms in order to recover complete bacterial chromosomes are poorly …

Evaluation Of A Human Papillomavirus Genotyping Assay For Cervical Cancer Screening In Tanzania, Kandali Kapie

School of Biological Sciences: Dissertations, Theses, and Student Research

Abstract: Mucosal high-risk Human papillomavirus (HR-HPV) has been identified as the primary factor in causing cervical cancer, the most common cancer in women of low and middle-income countries (LMICs). Cervical cancer screening, incorporating the HPV test shown to be more advantageous than screening by visual inspection with acetic acid (VIA) alone. However, due to resources constrain these countries could not afford the available HPV tests. We, therefore, validated a cost-effective Multiplex PCR HPV (mPCR) assay, a recently developed assay for detecting sixteen genital HPV, fourteen HR-HPV and 2 low-risk genotypes. We postulate that this HPV multiplex assay will be …

Contributions Of The Gp120 Variable Loops To Envelope Glycoprotein Trimer Stability In Primate Lentiviruses, Dane Bowder

School of Biological Sciences: Dissertations, Theses, and Student Research

Human Immunodeficiency Virus (HIV) is the etiological agent of AIDS and is responsible for the AIDS pandemic worldwide. According to UNAIDS, as of 2016, there were approximately 36.7 million people living with HIV globally, and 1.8 million new infections that year. While antiretroviral therapies and education continue to reduce these numbers, a preventative vaccine is still required to curb this epidemic. The envelope glycoprotein trimer of HIV, which is the sole protein on the surface of the virus and facilitates entry of the virus into host cells, is of keen interest to the HIV vaccine and drug-development field. Recently, the …

Influenza D Virus M2 Protein Exhibits Ion Channel Activity In Xenopus Laevis Oocytes, Evan Daniel Kesinger

School of Biological Sciences: Dissertations, Theses, and Student Research

The Influenza virus M2 ion channel has good potential as a target for antiviral drugs, as the channel is necessary for viral replication. M2 of Influenza A and B viruses has beenstudied extensively, and is understood to function as a proton channel. Antiviral drugs like amantadine and rimantadine have been used to block the function of Influenza A virus M2. Influenza C virus M2 has also been researched and is understood to act as a chloride ion channel. However, the M2 channel of Influenza D virus (DM2) has been studied very little, and the activity and mechanism of the channel …

Small Rna-Dependent Gene Silencing In The Green Alga Chlamydomonas Reinhardtii: Functions And Mechanisms, Eun Jeong Kim

School of Biological Sciences: Dissertations, Theses, and Student Research

Small RNAs (sRNAs), ~20-30 nucleotides in length, are non-coding RNAs that play essential roles in the regulation of gene expression in eukaryotes. They lead to inactivation of cognate sequences at the post-transcriptional level via a variety of mechanisms involved in translation inhibition and/or RNA degradation.

In the Chlorophyta Chlamydomonas reinhardtii, however, the molecular machinery responsible for sRNA-mediated translational repression remains unclear. To address the mechanisms of translation inhibition by sRNA, we have isolated an RNAi defective mutant (Mut26), which contains a deletion of the gene encoding the homolog of CCR4 in Chlamydomonas. We investigated the expression of …

Nitrogen Addition And Ecosystem Functioning: Changes In Species Composition Leaf Traits Amplify Increases In Leaf Area Index And Canopy Chlorophyll, Anna R. Tatarko

School of Biological Sciences: Dissertations, Theses, and Student Research

Increased nutrient inputs can cause shifts in plant community composition and plant functional traits, both of which affect ecosystem function. We studied community- and species-level changes in specific leaf area (SLA), chlorophyll, leaf thickness, leaf toughness, plant height and leaf dry matter content (LDMC) in a full factorial nitrogen (N), phosphorus (P), potassium (K) fertilization experiment in a semi-arid grassland. Nitrogen was the only nutrient addition to significantly affect leaf functional traits, and N addition increased community weighted SLA by 19%, leaf chlorophyll content by 34%, height by 26%, and resulted in an 11% decrease in LDMC while leaf thickness …

Behavioral Plasticity Across Non-Social Contexts In Female Green Swordtails, Xiphophorus Hellerii, Lindsey M. Coit

School of Biological Sciences: Dissertations, Theses, and Student Research

Phenotypic plasticity is the ability of an individual to alter its phenotype in response to environmental change. Individuals that express plasticity in behavior can quickly respond to changes that occur in the environment. Therefore, individuals that exhibit behavioral plasticity can alter their behavioral expression to best match current environmental conditions. The degree and direction of behavioral plasticity may be influenced by variation in individual characteristics. Understanding how variation in individual traits affects behavioral plasticity, and, whether patterns of behavioral plasticity are consistent across behavioral contexts are important topics to explore as we try to better understand how plasticity evolves and …

Variation In Density Dependent Seedling Survival Across Forests Of Different Successional Age And Hunting Protection Status, Nohemi Huanca-Nunez

School of Biological Sciences: Dissertations, Theses, and Student Research

Over 50% of the original extent of tropical forests has been cleared. Restoration of secondary forests is important for maintaining the ecosystem services that mature tropical forests provide. Density dependence (DD) is thought to be a major mechanism for shaping forest community structure and may cause reduced spatial aggregation among individuals of the same species, allowing for maintenance of diversity. While much research has focused on DD in mature tropical forests, few studies have examined how DD may influence community structure in secondary forests, many of which are also exposed to hunting. There are several important agents of negative and …