Bachelor of Science, Wittenberg University, 2022, Biochemistry/Molecular Biology

Antibiotic resistance in bacteria is becoming a significant concern, originating from the increased amount of antibiotics prescribed by doctors and patients failing to complete their course of treatment. Resistant bacteria are quickly adapting to new forms of antibiotics and are becoming more deadly. Based on the Centers for Disease Control and Prevention's 2019 estimate, in the United States approximately 2.8 million antibiotic resistant infections occur each year and about 90,000 deaths can be attributed to bacterial infections1. Therefore, it is essential that high school and undergraduate students interested in going into the medical field are introduced to the idea of antibiotic resistance. Several different methods of growing resistance to kanamycin and ampicillin in E. coli were created and tested to provide a laboratory experience to students at an introductory chemistry level. Multiple procedures were created using either solid or liquid medium, however, the most practical and successful procedure involved growing resistance in liquid medium in a single flask, which was left to grow over the course of a week. Additionally, the ability for already resistant strains to lose their inherent resistance was also tested through continually propagating cultures in liquid medium without antibiotic. It was found that, through this method, kanamycin resistance in E. coli could be lost in about three weeks or less.

Bachelor of Arts, Wittenberg University, 2022, Chemistry

According to the CDC, in the United States, about 3 million antibiotic resistant infections occur each year with 35,000 deaths from bacterial infections. The large quantity of antibiotics that are prescribed to patients increases the ability of bacteria to develop this resistance, especially when patients do not complete their full course of medication. With the development of bacterial resistance becoming a global phenomenon, it is crucial that the public become more educated on this issue. Toward this end, a method has been developed that demonstrates the growth of antibiotic resistance and could be incorporated into a high school or undergraduate laboratory curriculum. This lab experience would be ideal for students who are considering a medical or scientific research career, allowing them to witness resistance firsthand. It would also serve to educate other individuals, making them aware of the general issues associated with bacterial resistance. Over the course of a week, resistance is gradually evolved in E. coli. The students would then determine the minimum inhibitory concentration of the resistant strain and compare their value to the wildtype level.

Master of Science, The Ohio State University, 2023, Environment and Natural Resources

Antibiotic-resistant bacteria (ARB) pose a growing threat to public health by rendering antibiotic treatments ineffective and causing prolonged hospital stays, increased healthcare expenditures, and greater mortality. Of particular concern are those resistant to carbapenems, powerful antibiotics used for life-threatening infections. Carbapenem-resistant Enterobacteriaceae (CRE) and carbapenem resistance genes are established in surface waters through hospital and wastewater effluent. However, little is known about their presence in aquatic wildlife. Transmission of CRE from aquatic to terrestrial systems could introduce CRE into animal operations and subsequently the human food supply. Therefore, it is crucial to understand pathways of dissemination within and between aquatic and adjacent riparian organisms. This study investigated the effects of (1) fish-based ecological network structure and (2) trophic position and diet composition on carbapenem resistance in linked river-riparian reaches surrounding six wastewater treatments plants discharging into medium-to-large rivers in Cincinnati, Columbus, and Cleveland, Ohio. Carbapenem resistance was present at all six sites, with CRE genes recovered from multiple environmental samples over two sampling years. Carbapenem resistance was not observed in any samples of aerial insectivorous birds feeding in sample reaches (Tree Swallow Tachycineta bicolor). 10.5% of fish isolates exhibited carbapenem resistance, and 4.67% of fish isolates yielded CRE genes. Model selection of negative binomial models revealed that nutrient concentrations and turbidity were strongly supported predictors of carbapenem occurrence in fish communities. Ecological network properties including linkage density (i.e., number of interactions per species), compartmentalization (i.e., degree of connectedness of subgroups within a network), and variability in the magnitude of interactions were also important predictors. Carbapenem resistance generally (open full item for complete abstract)

Bachelor of Arts, Wittenberg University, 2019, Chemistry

The use of antibiotics to cure bacterial infections is one of the single most significant medical advancements in human history. This research focuses on the ability of bacteria to develop resistance to these antibiotics. The aminoglycoside antibiotic kanamycin was used to develop resistance in E. coli (ATCC 25922) as high above the minimum inhibitory concentration (MIC) as possible. Resistance was developed up to 2500 μg/mL of kanamycin, 100 times the MIC of 25 μg/mL. However, more frequently, resistance could be developed to 100 μg/mL. The antibacterial-resistant E. coli was then used in a cross-resistance study. This study aimed to find whether kanamycin resistance translated to resistance to other antibiotics. The kanamycin-resistant E. coli were tested against neomycin and gentamicin (both aminoglycosides) and ampicillin (a β-lactam). The kanamycin-resistance did not confer resistance to ampicillin, but resistance above the wild-type MIC was seen with gentamicin and to a larger extent with neomycin.

Master of Science (MS), Bowling Green State University, 2020, Biological Sciences

Multidrug resistant (MDR) pathogens are predicted to cause more than ten million annual deaths worldwide by 2050, making bacterial infections the leading cause of death. Although bacteria are evolving resistance to all known antibiotics, no large pharmaceutical companies are involved in drug discovery due to high cost and low profitability; thus, no new antibiotics are available, and the current ones are increasingly becoming ineffective at treating MDR infections. Moreover, recent studies suggest that there are few remaining new antibiotics in the environment left for discovery. Since MDR bacterial infections are predicted to be a major crisis, a new or augmented therapy to treat infections is imperative. Bacteriophage therapy is an alternative solution and has been internationally used for over 100 years. In bacteriophage therapy, phage bind to bacteria through specific protein-protein interactions that result in narrow host range infectivity. Although this specificity is beneficial because the interaction precisely targets a single pathogen, it is also problematic because a single phage usually cannot infect multiple strains of the same bacterial species. The phage discovery process to treat a specific pathogen is both time consuming and phage can fall short of the ability to antagonize multiple infections. Thus, phage with broad host range killing phenotypes are more beneficial when using phage therapy to treat infections caused by a particular pathogen. Therefore, this study set out to isolate phage with broad host range killing phenotypes such that phage that could inhibit more than one MDR pathogen could be found. In this study, 29 phage that antagonize cystic fibrosis (CF) derived MDR Pseudomonas aeruginosa were isolated from equine fecal water, purified, characterized through host range assays, and shown to kill two to eight CF derived MDR P. aeruginosa strains. Since phage have been shown to drive bacterial evolution toward increased antibiotic susce (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2019, Evolution, Ecology and Organismal Biology

Herbicide resistant weeds are among the greatest threats facing modern agriculture. Glyphosate, the active ingredient in the commercial herbicide RoundUp, is the most widely applied herbicide worldwide, and 43 weed species have evolved resistance to glyphosate to date. My research addressed four key questions about the strength, mechanisms, and fitness effects of glyphosate resistance using Conyza canadensis, a representative glyphosate-resistant weed, and Arabidopsis thaliana, a model plant species. In northcentral Ohio and southern Iowa, maternal biotypes (individual plants) of Conyza canadensis, also known as horseweed or marestail, were collected from 74 locations (both agricultural and non-agricultural) in both states. Dose-response experiments were used to categorize biotypes into resistance categories based on 80% survival at 0x only (Susceptible, S), and up to 1x (equivalent to 840 g ae ha-1; R1), 8x (R2), 20x (R3), and 40x (R4). Extreme glyphosate resistance (R4 biotypes) was quite common in both states and both habitats, and non-agricultural habitats served as a refuge for R4 biotypes. Glyphosate resistance mechanisms are generally presumed to impose a fitness cost due to possible trade-offs in resource allocation to plant defense, growth, and reproduction. Nine S, eight R1, and nine R4 biotypes originally collected in Iowa were grown in a common garden experiment in Iowa over two years and two sites to test for fitness effects. Based on early rosette sizes and days to bolting, nested ANOVAs showed that R4 biotypes grew as large as, if not larger than, both S and R1 biotypes, and bolted significantly earlier. Furthermore, R1 and R4 biotypes were less likely to display disease symptoms than S biotypes. Glyphosate resistance in horseweed appears not to impose an early growth penalty, and possibly no lifetime fitness cost. Specific mechanisms of glyphosate resistance in horseweed include altered translocation and vacuolar sequestration. Recently, a Canadi (open full item for complete abstract)

Master of Public Health, The Ohio State University, 2017, Public Health

Antimicrobial resistance (AMR) is a growing concern in human and animal medicine and threatens public health on a global scale. Beef cattle are a reservoir of Salmonella and have been implicated in foodborne outbreaks of AMR Salmonella in the U.S. Understanding trends in AMR and factors which affect resistance to medically important antibiotics in beef cattle is vital to animal and human health. The USDA's National Animal Health Monitoring System administered farm management questionnaires to beef feedlots in major cattle-feeding states around the U.S. and collected fecal samples from 100 feedlots in 1994, 73 feedlots in 1999, and 68 feedlots in 2011 for pathogen and AMR testing. The objectives of this study were to 1) evaluate change in the prevalence of AMR in Salmonella over time from USDA beef feedlot studies conducted in 1994, 1999, and 2011 and 2) to explore farm management factors, including antibiotic use, associated with the odds of AMR in a Salmonella isolate. Logistic regression models were created for each of four antibiotics: amoxicillin-clavulanic acid, ampicillin, ceftiofur, and trimethoprim-sulfamethoxazole. Final models were selected via backward elimination to measure statistical associations between management factors and odds of a Salmonella isolate being resistant to the antibiotic. There was a significant increase in odds of resistance from 1994 to 1999 for all four antibiotics, amoxicillin-clavulanic acid (OR=32.6), ampicillin (OR=6.1), ceftiofur (OR=115.4), and trimethoprim-sulfamethoxazole (OR=17.4). Isolates from 1999 had significantly higher odds of resistance compared with isolates from 2011 for amoxicillin-clavulanic acid (OR=3.8) and trimethoprim-sulfamethoxazole (OR=35.0). Use of antibiotics tylosin, tetracyclines, and sulfas as health or production management tools did not approach significance (p=0.20) in any of the four models. Management practices associated with increased odds of resistance to at least one antimicrobial included: (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Plant Pathology

Plants continually confront a multitude of environmental challenges that can impede their growth, development, and survival, and thereby have evolved a remarkable array of responses to environmental stresses to ensure their persistence on the landscape and optimize growth. These stress responses are remarkably plastic and adaptable to a changing environment and have been the subject of intense research interest. The study of plant stress responses provides critical insights into fundamental physiological processes and has practical implications for agriculture, conservation, and ecosystem management. Understanding the intricate signaling cascades and molecular components that underlie plant stress responses is essential for developing strategies to enhance stress tolerance in crops, mitigate the impact of climate change on ecosystems, and conserve plant biodiversity. In recurring encounters of tree species with both abiotic stress and pathogenic invasions, delimiting stress responses will be instrumental for conservation and management practices. Building on current understanding of induced resistance in the Pinus nigra - Diplodia spp. pathosystem, we hypothesized that, (1) predisposition of Austrian pine to abiotic stress such as climate change (CC) leads to increased susceptibility to pathogenic infections by Diplodia spp. and this heightened susceptibility is explainable by a detailed analysis of the transcriptional regulation of both the host and pathogen, (2) attack of Austrian pine by D. pinea results in a systemic induced resistance (SIR) phenotype that intensifies over time, and (3) this phenotype is mediated by the accumulation of terpenoids and is explainable by a detailed analysis of signaling pathways involving phytohormones in specific patterns. The test of the first hypothesis is described in Chapter 2. We subjected Austrian pine trees to simulated CC conditions of high temperatures and prolonged water scarcity, followed by infection with either D. p (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Plant Pathology

Phytophthora root and stem rot is one of the top ten most yield-limiting soybean [Glycine max (L.) Merr] diseases in the U.S. and Canada. The causal agent of this disease, Phytophthora sojae (Kaufmann & Gerdemann), is an oomycete (water mold) organism that is often managed by using disease-resistant soybean cultivars containing a single Rps gene to a specific pathotype of the pathogen combined with quantitative disease resistance (QDR). Due to the limitation of the number of effective Rps genes available, as the populations of this pathogen have adapted to these genes, it is a necessity to find new Rps genes and identify perfect markers for QDR genes, which have a smaller effect but can resist all pathotypes of P. sojae, that can be used in the development of modern soybean cultivars. In this dissertation, the main approach for all three chapters is to examine the mechanisms of disease resistance in soybeans towards P. sojae using different forward and reverse genetic approaches. A previous study found more than 100 candidate genes by mapping the expression quantitative disease-resistance loci (eQDRL) from the Conrad × Sloan population. To explore and validate the functions of these genes, a fast neutron (FN) population from the University of Minnesota, derived from soybean cultivar M92-220, with these genes deleted was employed. Thus, the first chapter's first objective was to compare cultivars M92-220 and Conrad at phenotypic and transcriptomic levels for their QDR resistance to determine if the molecular mechanisms associated with the eQDRLs were similar to those previously found in Conrad. Then, the next objective was to explore how the loss of the candidate genes using mutants that were highly susceptible would affect the soybean resistance response following inoculation with P. sojae by examining the three most susceptible FN mutants. Conrad and M92-220 were found to share high levels of QDR in the phenotypic assay as well as having several similar defense-r (open full item for complete abstract)

Master of Science (MS), Bowling Green State University, 2023, Biological Sciences

Bacterial pathogens are evolving resistance to all available antibiotics and are a leading cause of death worldwide. Thus, the discovery of new antibiotics that inhibit multi-drug resistant (MDR) pathogens is urgent. We hypothesize that environmental Pseudomonas strains that can inhibit the growth of MDR pathogens may be source of novel antibiotics that may have new or multiple mechanisms of action. We isolated 288 environmental Pseudomonas strains from the Portage River in northwest Ohio which represents a polluted water source. Pseudomonas strains were isolated and phylogenetically characterized using the gyrB housekeeping gene. To test our hypothesis, the environmental strains were competed against a collection of human and animal MDR pathogens including nine Burkholderia species, seven Staphylococcus aureus, and nine Pseudomonas aeruginosa strains, all isolated from lungs of cystic fibrosis patients, and five Aeromonas fish pathogens. Results from the 8,640 individual antagonistic assays showed that 115 of the environmental Pseudomonas strains demonstrated the ability to inhibit at least one pathogen. This suggests that these environmental strains may produce novel compounds which effectively inhibit these MDR pathogens. We performed transposon mutagenesis and screened for loss of inhibition mutants with strains J4D8, JA1H2, J1A5 and J3E11 to determine biosynthetic gene clusters involved in antibiotics production. Whole genome sequencing and arbitrary PCR coupled with antiSMASH were used to identify specific gene clusters involved in antagonistic activity. The compounds were predicted to include pyochelin, pyoverdine, MA026, lankacin C and cepacin A which are all derived from non-ribosomal peptides. Further analysis of these compounds is required to determine their novelty.

Doctor of Philosophy, Case Western Reserve University, 2022, Systems Biology and Bioinformatics

The evolution of therapeutic resistance in cancer is a complex and nearly inescapable process driven by evolutionary dynamics. As the genomic characterization of cancer has provided insight into the mechanisms of oncogenesis, tumor growth, and metastasis we have developed targeted therapeutics to provide personalized treatment based on mutation status. Yet, most cancer patients are not helped by these drugs, with just over 7\% of cancer patients in the United States benefiting from genome-driven care in 2020. In this work, we propose that an evolutionary-driven problem requires an evolutionary-inspired solution. We present a novel method for extracting therapeutic response biomarkers in cancer, and demonstrate its utility in large, publicly-available datasets, tightly-controlled in silico experiments, and translational efforts. Our procedure exploits principles of convergent evolution to find patterns across tumors with distinct evolutionary histories and mutational profiles. First, we use this signature extraction method to predict collateral treatment response in Ewing's sarcoma cell lines. While evolving resistance to standard of care treatment across multiple evolutionary replicates of a Ewing's sarcoma cell line, we compared gene expression between responders and non-responders to a variety of second-line treatments. Differential gene expression results were compiled to generate biomarkers of therapeutic response which are hypothesized to be clinically relevant, but require further validation. Next, we use epithelial cell lines from the Genomics of Drug Sensitivity in Cancer (GDSC) database to extract the Cisplatin Response Signature (CisSig). CisSig is predictive of cisplatin IC50 in GDSC cell lines, clinical trends in tumor sample databases, and survival outcomes in patients who received cisplatin-containing chemotherapy. Finally, we propose translational efforts to move two gene expression signatures, CisSig and the genome-adjusted radiation dose (GARD), (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2021, Pharmaceutical Sciences

The human DNA topoisomerase IIα (170 kDa, TOP2α/170) enzyme is essential in proliferating cells by functioning as a homodimer resolving DNA topological entanglements that form during chromosome condensation, replication, and segregation. The TOP2α/170 homodimer disentangles DNA by introducing transient double strand breaks in a DNA helix via a transesterification reaction between the active site Tyr805 from each TOP2α/170 subunit and the phosphodiester DNA backbone, creating the intermediate state known as the TOP2α/170-DNA cleavage complex. An intact DNA duplex passes through the cleaved DNA. Subsequently, the DNA strands are religated restoring the integrity of the DNA and preparing the TOP2α/170 dimer for another catalytic cycle. TOP2α/170 enzymatic activity is indispensable for the survival of highly proliferating cells including cancer cells. This has made TOP2α a prominent target for anticancer therapies. Some of the most widely used topoisomerase II targeting drugs such as etoposide, mitoxantrone, amsacrine and doxorubicin, stabilize the TOP2α/170-DNA cleavage complex preventing the religation of the DNA strands. As a result, these agents exert their cytotoxic effects by the accumulation of double strand DNA breaks which ultimately lead to the initiation of apoptotic pathways. Acquired chemoresistance to topoisomerase II targeting drugs continues to be a major obstacle in cancer treatment in the clinic. In order to characterize the mechanisms of resistance to etoposide, our laboratory developed etoposide resistant human leukemia K562 cells, designated K/VP.5 in which levels of TOP2α/170 were decreased along with identification of a novel C-terminal truncated isoform of TOP2α, TOP2α/90. This 90 kDa protein is present in both in K562 and etoposide resistant K/VP.5 cells with expression levels increased ~3-fold in K/VP.5 cells. TOP2α/90 is the translation product of novel alternatively spliced mRNA via intron 19 (I19) retention and processing, confirmed by 3 (open full item for complete abstract)

Honors Theses, Ohio Dominican University, 2021, Honors Theses

It is well-established that exercise plays a vital role in promoting a healthy lifestyle. The use of training programs incorporating aerobic and resistance training has become a common routine to achieve the benefits of good health. The main objective of this study was to determine the impact a virtual combined (aerobic and resistance) training program has on physical performance metrics and anthropometrics in females aged 20-29. We hypothesized that the use of a combined aerobic and resistance training program would lead to improvements in physical performance metrics and anthropometric measurements alike. This exercise intervention was a combined program consisting of both aerobic and resistance training exercises in accordance with the most recent American College of Sports Medicine (ACSM) physical activity guidelines. Ten participants completed the study (n=10) (Age: 22.7 ± 2.63 years, height: 166.2 ± 8.2 cm, weight: 77.75 ± 12.3 kg, BMI:28.6 ± 4.67). Eligibility requirements stated participants needed to be considered inactive prior to program start, achieving less than 120 minutes of moderate physical activity or 75 minutes of vigorous physical activity per week. This study utilized an individualized 4-week long training program which saw the application of both aerobic training and resistance training within each session, 3 times per week for a total of 45-50 minutes per session. The main exercise tests examined included: chair sit-to-stand, bench step-up, modified pushups, 12-minute walk test, and the sit-and-reach flexibility test, along with body mass index (BMI) and waist to hip ratio (WHR). The resulting data was examined via two-tailed paired-samples t-tests. This study demonstrated significant differences observed in physical performance exercises including increased chair-sit-stand (p=0.001), increased step-up test (p=0.01), and increased modified push-ups (p=0.01). There were no significant differences post-intervention between several of the physica (open full item for complete abstract)

Master of Arts (MA), Bowling Green State University, 2021, Theatre and Film

This thesis examines Palestinian theatre practices in the West Bank, Gaza Strip, and the Diaspora. Focusing on how theatre-makers within these contexts represent the Palestinian experience in relation to the ongoing Israeli settler-colonialism, I seek to offer a fuller definition of Palestinian theatre and highlight its different features. As non-violent resistance is a defining aspect of Palestinian artistic expression, I draw on a number of supporting theories to analyze how Palestinian theatre practitioners respond to the Israeli colonial practices as well as reflect on the ever-shifting socio-political realities of the Palestinian society. I begin by contextualizing the work of five major theatre companies in the West Bank and the creative tactics through which they contribute to the Palestinian culture of resistance, building on the work of Gabriel Varghese. I then introduce the concepts of sumud (steadfastness) and identity reaffirmation in an attempt to include theatre-makers in Gaza Strip and the Palestinian Diaspora. Throughout, I examine a number of plays and performances in relation to these concepts to demonstrate how Palestinians confront the conditions under which they live, while striving to preserve their cultural heritage. In doing so, I broaden the conversation on Palestinian theatre and the Palestinian context of non-violent resistance and what is at stake in how it is performed.

Master of Science in Biological Sciences, Youngstown State University, 2020, Department of Biological Sciences and Chemistry

Stenotrophomonas maltophilia OR02 (S. maltophilia 02) is a multi-metal resistant bacterium that was obtained from a heavy-metal contaminated site in Oak Ridge, TN. This location contains electromagnetic isotope processing centers that generated deleterious waste that was released into the surrounding environment in the form of mercury, uranium nitrate, and extensive heavy metals amalgamations. To survive under such conditions, metal resistant bacteria encode proteins that alter the toxicity of the metals in oxidation/reduction reactions, sequester them, or pump them out of the cell entirely. A gold-sensitive mutant was generated by introducing the EZ-Tn5TM transposome into S. maltophilia 02. This transposon, which carried a kanamycin resistance gene, randomly incorporated itself into the S. maltophilia 02 genome. 880 transformants were replica plated onto LB-kan plates, revealing a gold-sensitive S. maltophilia 02 mutant, A12. Liquid culture experiments showed that the minimal inhibitory concentration (MIC) for A12 was 170 μM gold chloride, whereas the wild type S. maltophilia 02 grew well into high concentrations of gold salts up to 190 μM. DNA sequencing and Basic Local Alignment Search Tool (BLAST) analysis showed that the transposon inserted itself after a hypothetical protein and downstream of genes for a DNA binding protein and a two- component sensor histidine kinase. BLAST analysis revealed a sequence similar to the sensor protein PhoQ, one component of a two-component histidine kinase.

Master of Science (MS), Bowling Green State University, 2019, Biological Sciences

The research described here focuses on the phylogenetic characterization of water-derived pseudomonads and their antagonistic activity against multi-drug resistance (MDR) P. aeruginosa and Burkholderia species. Phylogenetic work was based on the gyrB housekeeping gene. Genetic techniques have been optimized and employed to identify genes associated with antimicrobial production via transposon (Tn) mutagenesis using a triparental mating system approach with Pseudomonas as the model organism. This study expands on theses previous studies in the lab to identify biosynthetic gene clusters (BGC) involved in production of novel antibiotics capable of inhibiting the growth of MDR pathogens. We utilize a previously optimized workflow to identify genes from environmental isolates involved in the inhibition of MDR P. aeruginosa and species within the Burkholderia cepacia complex (Bcc). We show that both MDR Bcc and P. aeruginosa pathogens were inhibit by environmental Pseudomonas strains. Out of 7,784 interactions, 210 of these were antagonistic. Superkillers (SK), defined as strains that inhibit ≥3 of MDR pathogens, were selected for optimization of Tn mutagenesis to identify gene cluster whose products inhibit these MDR pathogens. Only six out of the 24 SK's were capable of this process. Out of these six, three were selected for large scale mutagenesis to identify loss of inhibition (LOI) mutants. Four LOI mutations were found for strain S5F11, one of which had an insertion within a BGC predicted to produce an NRPS complex. Seven LOI mutants were found for S3E7. Although none of these insertions were identified within a BGC, genes have been identified that are observed to be heavily involved in antibiotic production. This study suggests that environmental Pseudomonas strains have the capacity to inhibit the growth of CF-derived MDR pathogens. Using Tn mutagenesis, we have identified novel loci that are associated with antibiotic production.

PHD, Kent State University, 2018, College of Arts and Sciences / Department of Biological Sciences

In urban streams, contaminants such as antibiotics, ARGs, nutrients, and metals, co-occur with anthropogenic activities. These toxicants can have a profound effect on microbial community composition, which may, in turn, affect microbial community function. Such results suggest that the composition and function of microbial communities are consequences of their response to environmental stimuli. However, the differing physiological responses of microorganisms to environmental stressors suggests that community structure may be an important factor driving the community's functional responses to avoid or reduce the effects associated with physiochemical changes in the environment. With the projected increase in concurrent environmental stressors associated with the anthropogenic activity, there is a need to understand how microbial communities respond to compounded stressors. The overarching question for my dissertation is: how does chemical stress (in the form of heavy metals) interact with other environmental factors (including hydrologic conditions and nutrients) to impact microbial community structure and function in streams? To address this question, I utilized a combination of trait-based molecular approaches in tandem with biological and chemical field measurements and laboratory experiments. I looked at how microbial, specifically bacterial and diatom, community composition, structure, and function were affected by different stresses that are found within urban streams.

MS, University of Cincinnati, 2018, Arts and Sciences: Biological Sciences

A survey for the presence of antibiotic-resistant E. coli was undertaken by collecting samples from seven geographically dispersed US wastewater treatment plants (WWTPs). Samples were collected at each WWTP in cool and summer months and cultured using selective media. The resulting E. coli isolates were characterized for resistance to imipenem, ciprofloxacin, cefotaxime and ceftazidime, presence of carbapenemase and extended spectrum beta lactamase (EBSL) genes, and phylogroups and sequence types (STs). The survey identified 322 antibiotic-resistant (AR) E. coli isolates and characterized the associated resistance profiles, with 65 of these being imipenem-resistant. Of the 65 carbapenem-resistant E. coli (CREC) isolates, 62% contained = 1, and 31% contained = 2, of nine studied carbapenemase and ESBL genes. The most common carbapenemase gene detected was blaVIM and two instances of blaKPC were found. However, the gene panel was negative for many of the CREC isolates. Carbapenem resistance was seen in pathogenic E. coli phylogroups (B2 & D) and STs (1193, 405, 648) as well as commensal phylogroups (A & C). The occurrence of CREC in wastewater is a potential concern because this matrix may serve as a reservoir for gene exchange and thereby increase the risk of AR bacteria (including CR) being disseminated into the environment and thence back to humans.

Master of Science in Biological Sciences, Youngstown State University, 2018, Department of Biological Sciences and Chemistry

Stenotrophomonas maltophilia Oak Ridge strain 02 (S. maltophilia 02) was isolated from a heavy metal contaminated stream, East Fork Poplar Creek in Oak Ridge, Tennessee. This strain has high levels of resistance to both metals and antibiotics. All strains of S. maltophilia are gram-negative bacilli. Some strains are opportunistic pathogens that are resistant to high levels of metals and to antibiotics such as cephalosporins, quinolones, carbapenems, penicillins, and ß-lactam/ß-lactamase inhibitor combinations. S. maltophilia 02 contains two ß-lactamase genes, L1 and L2. In this study, the L2 ß-lactamase and its regulator, LysR, were cloned and sequenced. MICs were performed to test for antibiotic resistance against ampicillin, showing resistance even at 1500 µg/ml. In addition, L2 was also found to confer resistance to the antibiotic carbenicillin, but not to cefoxitin. By studying penicillin resistance mechanisms, it may be possible to develop strategies to combat drug resistance in pathogenic strains of S. maltophilia.

Doctor of Philosophy, The Ohio State University, 2018, Plant Pathology

Numerous diseases affect soybean [Glycine max (L.) Merr] yields throughout the growing season in Ohio. Two soil borne pathogens Fusarium graminearum and Phytophthora sojae are known to reduce stand and yield. Currently, fungicide seed treatments are used to manage these pathogens, however, host plant resistance is often the best management strategy for field crops. Thus, the overall objective of the five chapters this dissertation was to identify mechanisms and candidate genes of resistance that are effective towards seed, seedling, and root rots caused by Fusarium graminearum and P. sojae in soybean. Quantitative disease resistance loci (QDRL) have been mapped in two separate recombinant inbred line (RIL) populations for resistance to Fusarium graminearum . In the F7:8 RIL derived from a cross Magellan X PI 567516C, one major QDRL was mapped. Fine mapping of this region identified four putative candidate genes for resistance to Fusarium graminearum . In an additional population of Wyandot x PI 567301B, a major and minor QDRL was mapped to chromosome 8 and 6, respectively. Hybrid genome assembly, fine mapping, and RNA sequencing analysis narrowed the major QDRL to 2.5 cM containing three putative candidate genes for resistance or susceptibility. To validate these candidate genes functional analysis needs to be assessed at the seed level. To achieve this we modified the Apple latent spherical virus (ASLV) which allowed for direct inoculation of VIGS-triggering ALSV agro-infiltrated Nicotiana benthamiana leaves onto soybean unifoliates. However, this method is genotype dependent; the virus is detected in numerous reproductive structures including pods, embryos, stems, leaves, and roots. The last objective of this dissertation focuses on mechanisms of partial resistance to Phytophthora sojae . This oomycete is a leading pathogen of soybean, causing root and stem rot (PRR) across the North Central Region in the U.S. Twenty phenotypic quantitative trait loci ( (open full item for complete abstract)