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The experiments conducted in this report supported previous evidence (Bethany et al., 2019) that a newly identified predatory bacterium causes a higher rate of mortality in the biological soil crust cyanobacterium M. vaginatus when in hot soils than in cold soils. I predicted that the extracellular propagules of this predatory bacterium were inactivated at seasonally low temperatures, rendering them non-viable when introduced to M. vaginatus at room temperature. However, I found that the predatory bacterium became only transiently inactive at low temperatures, recovering its pathogenicity when later exposed to warmer temperatures. By contrast, inactivation of infectivity was complete by exposure in both liquid and dry conditions for five days at 40 °C. I also expected that its infectivity towards M. vaginatus was temperature dependent. Indeed, infection was hampered and did not cause high mortality when predator and prey were incubated at or below 10 °C, which could have been due to slowed metabolisms of M. vaginatus or to an inability of the predatory bacterium to attack in cold conditions. Above 10 °C, when M. vaginatus grew faster, time to full death of predator/prey incubations correlated with the rate of growth of healthy cultures.
The experiments in this study observed a correlation between the growth rate of uninfected cultures and the decay rate of infected cultures, meaning that temperatures that cultures that displayed a higher growth rate for uninfected M. vaginatus would die faster when infected with the predatory bacterium. Infected cultures that were incubated at temperatures 4 and 10 °C did not display death and this could have been due to lower activity of M. vaginatus at lower temperatures or the inability for the predatory bacterium to attack at lower temperatures.
The experiments in this study observed a correlation between the growth rate of uninfected cultures and the decay rate of infected cultures, meaning that temperatures that cultures that displayed a higher growth rate for uninfected M. vaginatus would die faster when infected with the predatory bacterium. Infected cultures that were incubated at temperatures 4 and 10 °C did not display death and this could have been due to lower activity of M. vaginatus at lower temperatures or the inability for the predatory bacterium to attack at lower temperatures.
ContributorsAhamed, Anisa Nour (Author) / Garcia-Pichel, Ferran (Thesis director) / Giraldo Silva, Ana Maria (Committee member) / Bethany Rakes, Julie (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
With opioid use disorder (OUD) being an epidemic, it is important to investigate the mechanisms as to why this is so. This study established a self-administration paradigm to model and investigate the mechanisms of polysubstance, sequential use in conjunction with the analysis of withdrawal symptomatology driven by opioid withdrawal. The independent variables were dichotomized into the control group (food/cocaine) and the experimental group (oxycodone/cocaine). We hypothesized that more cocaine would be self-administered on the first day of oxycodone withdrawal. In addition, we hypothesized that somatic signs of withdrawal would increase at 16 hours post-oxycodone self-administration. Finally, we hypothesized that cocaine intake during oxycodone withdrawal would potentiate subsequent oxycodone self-administration. Our findings revealed that animals readily discriminated between the active (food or oxycodone) and inactive levers - but will however require more animals to achieve the appropriate power. Further, the average cocaine infusions across phases exhibited significance between the oxycodone/cocaine and food/cocaine group, with the average cocaine infusions being lower in food than in oxycodone-experienced animals. This implies that the exacerbation of the sequential co-use pattern in this case yields an increase in cocaine infusions that may be driven by oxycodone withdrawal. Further, to characterize withdrawal from oxycodone self-administration, somatic signs were examined at either 0 or 16 hrs following completion of oxycodone self-administration. The oxycodone/cocaine group exhibited significantly lower body temperature at 16 hrs of oxycodone withdrawal compared to 0 hrs. No differences in somatic signs of withdrawal in the food/cocaine group was found between the two timepoints. Oxycodone withdrawal was not found to potentiate any subsequent self-administration of oxycodone. Future research is needed to uncover neurobiological underpinnings of motivated polysubstance use in order to discover novel pharmacotherapeutic treatments to decrease co-use of drugs of abuse. Overall, this study is of importance as it is the first to establish a working preclinical model of a clinically-relevant pattern of polysubstance use. By doing so, it enables an exceptional opportunity to examine co-use in a highly-controlled setting.
ContributorsUlangkaya, Hanaa Corsino (Author) / Gipson-Reichardt, Cassandra (Thesis director) / Olive, M. Foster (Committee member) / Department of Psychology (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Alzheimer’s disease (AD) is a progressive cognitive and behavior disorder that is characterized by the deposition of extracellular Aβ plaques, intracellular neurofibrillary tangles, and neuroinflammation. Aβ is generated by cleavage of the amyloid precursor protein (APP) by β-secretase (BACE1) and, subsequently, y- secretase. In recent years, there has been an increasing interest in studying and understanding inflammation as a therapeutic target for AD. Inflammation manifests in the brain in the form of activated microglia and astrocytes. These cells are able to release high levels of inflammatory cytokines such as Tumor Necrosis Factor-α (TNF-α). TNF-α is a major cytokine, which is involved in early inflammatory events and plays a role in the progression of AD pathology. There are currently no treatments that target chronic neuroinflammation. However, previous work in our laboratory with transgenic mice modeling AD suggested that the anti-cancer drug lenalidomide could lower neuroinflammation and slow AD progression, though the cellular and molecular mechanisms are yet to be elucidated. Here we hypothesized that lenalidomide can modulate TNF-α production in microglia and decrease amyloidogenesis. Using immortal cell lines mimicking several brain cell types, we discovered that lenalidomide is likely to decrease inflammation by modulating microglia cells rather than neurons or astrocytes. In addition, the drug may prevent the overexpression of BACE1 upon inflammation, thus blocking the overproduction of Aβ. If confirmed, these results could lead to a better understanding of how inflammation regulates Aβ synthesis and provide novel cellular and molecular therapeutic targets to control the progression AD.
ContributorsGujju, Manasa (Author) / DeCourt, Boris (Thesis director) / Olive, M. Foster (Committee member) / Department of Psychology (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The gastrointestinal (GI) tract is home to a complex and diverse microbial ecosystem that contributes to health or disease in many aspects. While bacterial species are the majority in the GI tract, their cohabitants, fungal species, should not be forgotten. Children with autism spectrum disorder (ASD) often suffer from GI disorders and associated symptoms, implying a role the bacterial and fungal gut microbiota play in maintaining human health. The irregularities in GI symptoms can negatively affect the overall quality of life or even worsen behavioral symptoms the children present. Even with the increase in the availability of next-generation sequencing technologies, the composition and diversities of fungal microbiotas are understudied, especially in the context of ASD. We therefore aimed to investigate the gut mycobiota of 36 neurotypical children and 38 children with ASD. We obtained stool samples from all participants, as well as autism severity and GI symptom scores to help us understand the effect the mycobiome has on these symptoms. By targeting the fungal internal transcribed spacer (ITS) and bacterial 16S rRNA V4 regions, we obtained fungal and bacterial amplicon sequences, from which we investigated the diversities, composition, and potential link between two different ecological clades. From fungal amplicon sequencing results, we observed a significant decrease in the observed fungal OTUs in children with ASD, implying a lack of potentially beneficial fungi in ASD subjects. We performed Bray-Curtis principal coordinates analysis and observed significant differences in fungal microbiota composition between the two groups. Taxonomic analysis showed higher relative abundances of Candida , Pichia, Penicillium , and Exophiala in ASD subjects, yet due to a large dispersion of data, the differences were not statistically significant. Interestingly, we observed a bimodal distribution of Candida abundances within children with ASD. Candida's relative abundance was not significantly correlated with GI scores, but children with high Candida relative abundances presented significantly higher Autism Treatment Evaluation Checklist (ATEC) scores, suggesting a role of Candida on ASD behavioral symptoms. Regarding the bacterial gut microbiota, we found marginally lower observed OTUs and significantly lower relative abundance of Prevotella in the ASD group, which was consistent with previous studies. Taken together, we demonstrated that autism is closely linked with a distinct gut mycobiota, characterized by a loss of fungal and bacterial diversity and an altered fungal and bacterial composition.
ContributorsPatel, Jigar (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Kang, Dae Wook (Committee member) / Adams, James (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The effect of an anaerobic reductive environment produced by the oxidation of zero valent iron (ZVI) on the microbial reductive dechlorination of trichloroethylene and its applicability to in-situ bioremediation processes was investigated using microcosms and soil column studies. I learned that microbial dechlorination requires a highly reductive environment, as represented by negative values for oxidation-reduction potential (ORP), which can be maintained through the addition of reducing agents such as ZVI, or to a lesser extent, the fermentation of added substrates such as lactate. Microcosm conditions represented distance from an in-situ treatment injection well and contained different types of iron species and dechlorinating bioaugmentation cultures. Diminishing efficacy of microbial reductive dechlorination along a gradient away from the injection zone was observed, characterized by increasing ORP and decreasing pH. Results also suggested that the use of particular biostimulation substrates is key to prioritizing the dechlorination reaction against competing microbial and abiotic processes by supplying electrons needed for microbial dechlorination.
ContributorsMouti, Aatikah (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Delgado, Anca (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
Nicotine addiction remains a prevalent public health issue, and the FDA has released a statement outlining the systematic reduction of nicotine to non-zero levels in the coming years. Current research has not yet established the effects of abrupt nicotine dose reduction on vulnerability to relapse, nor has abrupt nicotine dose reduction been evaluated in terms of behavioral economic characteristics of demand and elasticity been evaluated for reduced doses of nicotine. Using a rat model, we first evaluated the comparability of between- and within-session protocols for establishing characteristics of demand and elasticity for nicotine to shorten experimental timelines for this study and future studies. We then tested environmental enrichment and sex as factors of elasticity of demand for nicotine. Using a rat model of relapse to cues, we also examined the effects of nicotine dose-reduction on vulnerability to relapse. We found differences in maximum consumption and demand between the between- and within-session protocols, as well as sex differences in elasticity of demand on the within-session protocol where male demand was more elastic than female demand. Additionally, we found that enrichment significantly increased elasticity of demand for nicotine for both males and females. Finally, preliminary analyses revealed that nicotine dose reduction yields more inelastic demand and higher maximum consumption, and these outcomes predict increased time to extinction of the association between nicotine and contingent cues, and increased rates of relapse. These studies highlight the usefulness and validity of within-session protocols, and also illustrate the necessity for rigorous testing of forced dose reduction on nicotine vulnerability.
ContributorsCabrera-Brown, Gabriella Paula (Author) / Gipson-Reichardt, Cassandra (Thesis director) / Olive, M. Foster (Committee member) / Davis, Mary (Committee member) / Sanford School of Social and Family Dynamics (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
Hydrogen is a key indicator of microbial activity in soils/sediments and groundwater because of its role as an electron donor for reducing sulfate and nitrate and carrying out other metabolic processes. The goal of this study was to quantitatively measure the total biological hydrogen demand (TBHD) of soils and sediments in anaerobic environments. We define the total biological hydrogen demand as the sum of all electron acceptors that can be used by hydrogen-oxidizing microorganisms. Three sets of anaerobic microcosms were set up with different soils/sediments, named Carolina, Garden, and ASM. The microcosms included 25g of soil/sediment and 75 mL of anaerobic medium. 10 mL of hydrogen were pulse-fed for 100 days. Hydrogen consumption and methane production were tracked using gas chromatography. Chemical analysis of each soil was performed at the beginning of the experiment to determine the concentration of electron acceptors in the soils/sediments, including nitrate, sulfate, iron and bicarbonate. An analysis of the microbial community was done at t = 0 and at the end of the 100 days to examine changes in the microbial community due to the metabolic processes occurring as hydrogen was consumed. Carolina consumed 9810 43 mol of hydrogen and produced 19,572 2075 mol of methane. Garden consumed 4006 33 mol of hydrogen and produced 7,239 543 mol of methane. Lastly, ASM consumed 1557 84 mol of hydrogen and produced 1,325 715 mol of methane. I conclude that the concentration of bicarbonate initially present in the soil had the most influence over the hydrogen demand and microbial community enrichment. To improve this research, I recommend that future studies include a chemical analysis of final soil geochemistry conditions, as this will provide with a better idea of what pathway the hydrogen is taking in each soil.
ContributorsLuna Aguero, Marisol (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Delgado, Anca (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
In the United States, the prevalence of pediatric obesity has increased to 17% in the general population and even more so in the Hispanic pediatric population to 22.4%. These children are at a higher risk for associated comorbidities, including cardiovascular disease and insulin resistance. The purpose of the following study is to determine the effectiveness of the Nutrition and Health Awareness curriculum at reducing childhood obesity by evaluating alterations in the gut microbial composition, diet, and overall health of the students throughout the five-week program. Nutrition and Health Awareness (NHA) is a student organization that strives to reduce the prevalence of obesity, diabetes, and cardiovascular diseases, specifically in children, by providing active nutrition education services through peer mentoring in elementary schools and community programs. This study went through ASU's Institutional Review Board process and all forms were translated into Spanish. The control group maintained their normal routines and the experimental group received the 5 week NHA program and then continued with their normal routines. Anthropometric measures (Body Mass Index, waist-to-hip ratio, and blood pressure), diet measures (Hispanic food frequency questionnaire), fecal swabs, and content surveys were collected on weeks 0, 5, and 8. Contrary to expected, alpha diversity, kilocalorie intake, and macronutrient intake decreased as the study progressed for both the control and experimental groups. Anthropometric measurements were relatively stable. Though not statistically significant, the greatest difference in time points is between weeks 1 and 8. This decrease in alpha diversity and kilocalorie intake could be due to a change in environment since the children started school on week 8. Future implications of this study are that parental involvement is necessary for an effective, sustainable change in these children. More research in different settings is necessary to determine NHA's effectiveness
ContributorsPatel, Kapila Cristina (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Whisner, Corrie (Committee member) / School of Nutrition and Health Promotion (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Microorganisms can produce metabolites in the gut including short chain fatty acids, vitamins, and amino acids. Certain metabolites produced in the gut can affect the brain through changes in neurotransmitter concentrations. Serotonin, a neurotransmitter, is associated with mood, appetite, and sleep. Up to 90% of serotonin synthesis is located in the gut, by human enterochromaffin cells. Bacteria known to biosynthesize tryptophan, precursor to serotonin, include Escherichia coli, Enterococcus and Streptococcus. Tryptophan is synthesized by bacteria with the enzyme tryptophan synthase and requires Vitamin B6 (Pyridoxal). We hypothesize that gut isolates from surgical weight loss patients can enhance tryptophan production, which relies on vitamin B6 availability. Our goal was to isolate bacteria in order to test for tryptophan production and to determine how Vitamin B6 concentrations could affect tryptophan production. We isolated gut bacteria was from successful surgical weight loss patient with selective pressures for Enterobacter isolates and Enterococcus isolates. We tested the isolates were tested to determine if they could biosynthesize tryptophan in-vitro. Bacterial cultures were enriched with yeast and enriched with serine and indole, substrates necessary for tryptophan biosynthesis. We analyzed the supernatant samples for tryptophan production using GC-FID. Bacterial isolates most closely related to E. coli and Klebsiella based on 16S rRNA gene sequences, produced tryptophan in vitro. While under serine & indole media conditions, R1, the isolate most similar to Klebsiella produced more tryptophan than R14, the isolate most similar to E. coli. We tested the R1 isolate with a gradient of vitamin B6 concentrations from 0.02 µg/mL to 0.2 µg/mL to determine its effect on tryptophan production. When less than 0.05 µg/mL of Vitamin B6 was added, tryptophan production at 6 hours was higher than tryptophan production with Vitamin B6 concentrations at 0.05 µg/mL and above. The production and consumption of tryptophan by Klebsiella under 0 µg/mL and 0.02 µg/mL concentrations of Vitamin B6 occurred at a faster rate when compared to concentrations 0.05 µg/mL or higher of Vitamin B6.
ContributorsYee, Emily L. (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Ilhan, Zehra (Committee member) / W. P. Carey School of Business (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Cases of heroin use and overdose are on the rise in the United States which has created what some call a public health crisis. Previous studies have investigated the beneficial effect of social interaction recovering addicts, and in animal models of addiction, social interaction can prevent or reverse the conditioned rewarding effects of cocaine. This study sought to determine if social interaction would prevent or diminish a conditioned preference for a heroin-paired context. Following establishment of baseline place preference, adult male Sprague-Dawley rats underwent once daily conditioning with either saline, heroin (1 mg/kg), or the animal's cage-mate for a total of 8 conditioning sessions. Assessment of post-conditioning place preference revealed that both the heroin injections and the presence of the cage-mate produced a place preference . In contrast to the findings of previous studies using cocaine as the conditioning drug, it was determined that rats preferred the heroin-paired context over that paired with the cage-mate.. These findings suggest that the protective effects of social interaction found in prior studies using cocaine as the conditioning drug may not extend to opiates, perhaps a result of stronger contextual conditioning and/or rewarding effects of this class of abused drugs.
ContributorsMarble, Krista Lillian (Author) / Olive, M. Foster (Thesis director) / Tomek, Seven (Committee member) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12