Published ETD Collection
Permanent URI for this collectionhttps://hdl.handle.net/10657/2
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Browsing Published ETD Collection by Subject "16S rRNA"
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Item Graphene and Graphene Oxide Toxicity and the Impact to Environmental Microorganisms(2017-08) Nguyen, Hang Ngoc; Rodrigues, Debora F.; Hu, Yandi; Louie, Stacey M.; Robles Hernandez, Francisco C.; Castro-Wallace, Sarah L.; Robertson, Megan L.In natural and engineered environments, such as landfills and wastewater treatment plants, microorganisms are responsible for cleaning the environment by digesting and biodegrading contaminants. Antimicrobial pollutants can seriously hinder the functionality of native microbial populations leading to ineffective removals of biological and chemical wastes. Additionally, microorganisms can have deleterious effects to society through diseases and food spoilage. Therefore, it is essential to understand the effect of these nanomaterials on microbial populations as well as their role in hindering microbial activities, such as biological wastewater treatment and antimicrobial properties, to keep the environment balanced and to develop safe antimicrobial applications. This study presents the effects of graphene (G) and graphene oxide (GO) to fungi and bacteria to identify their impact to the environment and antimicrobial properties for potential applications. These nanomaterials were shown to inhibit significantly fungal growth and their mechanisms of inactivation involved apoptosis of the fungal hyphae. Acute and chronic toxicity to bacterial communities was also investigated in wastewater. The presence of high concentrations of these nanomaterials in the acute assays affected the carbon, nitrogen and phosphorus biogeochemical cycles significantly. While the chronic assay, showed that the bacterial population shifted differently in the presence of G or GO. Overall, GO was shown to have a more pronounced toxicity than G to the microbial communities in activated sludge. The antimicrobial properties of these nanomaterials were further explored for application as antimicrobial coatings with polymeric adhesives. The coatings with polymeric adhesives were effective against a wide range of bacteria and did not present cytotoxicity to human corneal epithelial cells, which implied these coatings are promising for biomedical applications.Item Methamphetamine Exposure and Withdrawal Impact Gut Microbiota and Induce Depressive-Like Behavioral Effects on Rodents.(2019-05) Forouzan, Shadab; Kosten, Therese A.; Lee, Sunbok; Meisch, Richard A.Methamphetamine (MA) is one of the most frequently used amphetamine-type stimulants in the United States. Individuals who repeatedly abuse MA can develop MA use disorder (MuD)—a chronic, relapsing condition often triggered by withdrawal symptoms that develop following cessation of use. Long term abuse MA can result in negative health consequences including extreme weight loss, severe dental problems, malnutrition, confusion, insomnia, mood disturbances, and violent behavior. Importantly, depression and anxiety are key diagnostic characteristics of MA withdrawal in humans. Despite the well-documented dangers of chronic MA use, approximately 1.2 million people reported using MA in the past year. Given the lack of effective treatments for those with MuD, novel therapeutic targets must be considered. One potential target is the gut microbiome, which has an important influence on brain, behavior, and health as a part of the gut-brain axis. The gut microbiome comprises microorganisms and their genomes that reside in the intestinal tract. Therefore, the use of psychobiotics may provide a new way for treatments for drug addiction. In this study, we evaluated the effects of MA administration (2 mg/kg, s.c.) on withdrawal- induced behaviors and in the gut microbiota in male Sprague-Dawley rats (n=8). 16 male rats (60-70 days old) were divided equally into 2 groups: METH and Vehicle (control) groups. Rats in METH group were given twice daily injection of Saline (s.c) for 14 days, during which baseline behaviors (elevated plus maze (EPM) for anxiety-like behavior; forced swim test (FST) for depressive-like behavior) were assessed. Next, rats were given twice daily injections of MA for 14 days, followed by 7 days of withdrawal, during which performance on the Elevated Plus Maze (EPM), Open Field Task (OFT), and Forced Swim Task FST were assessed. Control group were given twice daily injection of Saline (s.c.) for 28 days, followed by 7 days of withdrawal. Fecal collection for microbiome analyses occurred on day 5 of saline administration, day 1, 7, 14 of MA administration, at 24-, 48- and 96-h, and day 7 of withdrawal, during which performance on the EPM, OFT, and FST were assessed. Results indicated that MA withdrawal increased depressive-like behavior, with an increase in immobility time in the FST (p<0.05). Anxiolytic/anxiogenic effects were not observed in either group. We analyzed the gut microbiome composition of each group through 16S rRNA gene sequencing. Results revealed MA administration and withdrawal significantly changed the relative abundances of several bacterial phyla. Compared to control group, the METH group demonstrated a higher abundance of Firmicutes, Verrumcomicrobia, Actinobacteria, Tenericutes, and Proteobacteria (p <0.05, vs. saline), and lower abundance of Bacteroidetes (p <0.05, vs. saline). At the genus level, Allobaculum, Bifidobacterium, and Lactobacillus were significantly more abundant in the fecal microbiota of METH group than vehicle group during MA administration and early days of withdrawal and they were normalized completely after 7 days of withdrawal. No significant changes in Shannon diversity were observed. These findings provide direct evidence that administration of MA causes gut dysbiosis and withdrawal from chronic methamphetamine induces depressive-like but not anxiety-like behavioral effects in male rodents. Our observation will contribute to a better understanding of the function of gut microbiota in the process of drug abuse and guide the choice of target therapeutics for MuD to test in future studies.