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Many aspects of biological function are affected by hormones, from physiology to behavior, and the synthesis and release of hormones in vertebrates are regulated by the endocrine axes of control. A growing body of research shows that the mechanisms underlying the endocrine axes of control are complex and interconnected, with many hormones having multiple effects, and with many interactions between axes. In this study, I examined the effects of decreased thyroid function on the glucocorticoid stress response in Japanese quail, a potential interaction between the hypothalamic-pituitary thyroid (HPT) and hypothalamic-pituitary adrenal (HPA) axes of control. I used the thyroid inhibitor ammonium perchlorate (AP) for 2 weeks and 5 weeks to induce two states of decreased thyroid function: a thyroid challenged state, in which birds have depleted thyroidal T4 content, but still maintain euthyroid (normal) concentrations of plasma T4, and a hypothyroid state, in which birds have depleted thyroidal T4 content and decreased concentrations of plasma T4. Thyroid function was assessed by measuring plasma T4 concentrations, thyroidal T4 content, and thyroid gland mass. I took blood samples from birds both immediately prior to and immediately following a 30 minute confinement and agitation stressor to evaluate the effects of decreases in thyroid function on basal and stress-induced plasma corticosterone and plasma T4 concentrations. I found two key results: First, although baseline levels of plasma corticosterone were unchanged, the corticosterone stress response was significantly blunted in both the thyroid challenged and hypothyroid birds as compared to controls. This finding suggests that the HPT and HPA axes are functionally connected in birds, and other evidence suggests this connection is likely at the pituitary or hypothalamic level. Second, in hypothyroid birds, plasma T4 concentrations were elevated (into the euthyroid range) in response to the experimental stressor, although no change in plasma T4 was observed in thyroid challenged or control birds. This finding suggests that plasma T4 may have a permissive role in mounting a stress response. / Master of Science in Life Sciences

Perchlorate contamination of drinking water sources in the United States is widespread and represents a public health concern. Biological treatment is an attractive option because perchlorate-reducing bacteria (PRB) are ubiquitous in the environment and can reduce perchlorate completely to chloride. Treatment of perchlorate-contaminated water in fixed-bed bioreactors has been demonstrated at the laboratory- and pilot-scale. However, full-scale development of reliable biological drinking water treatment processes requires a better understanding of the microbial ecology and activity of perchlorate-reducing communities in bioreactors. The objective of this research was to develop molecular biology tools (MBTs) to quantify PRB and expression of genes required for complete perchlorate reduction (pcrA and cld). The development of MBTs targeting specific genes requires that the sequence of the genes be known. In this work, an MBT called prokaryotic Suppression Subtractive Hybridization (SSH) PCR complementary DNA (cDNA) Subtraction was developed to rapidly isolate target genes for sequencing. This new tool was developed and validated using the model bacterium Pseudomonas putida mt-2 and the model pollutant toluene. For this system, over 90% of the isolated gene fragments encoded toluene-related enzymes, and 20 distinct toluene-related genes from three key operons were identified. Based on these results, prokaryotic SSH PCR cDNA Subtraction shows promise as a targeted method for gene identification; however, application to a PRB did not yield new pcrA and cld sequences. Therefore, to support the development of biological perchlorate treatment processes, quantitative PCR (qPCR) and reverse transcription qPCR (RT-qPCR) assays targeting pcrA and cld were developed using existing sequences. The qPCR and RT-qPCR assays were applied to a laboratory-scale bioreactor and two pilot-scale bioreactors treating perchlorate-contaminated water. Higher quantities of perchlorate reduction genes and transcripts generally were observed when bioreactor performance was superior. Although no quantitative correlations were established, these assays detected differences in the quantity of PRB and changes in gene expression levels during the course of bioreactor operation and between bioreactors with different performance levels. Furthermore, these assays provided an additional line of evidence that microbial perchlorate reduction was occurring. This marks the first application of qPCR assays to quantify perchlorate reduction genes and transcripts in bioreactors. / text

Perchlorate has entered human and environmental food chains and has received a great deal of attention because of its toxicity to humans. In this study, chemical degradation of perchlorate was investigated using partially oxidized titanium ions (Ti2+ and Ti3+) in solutions and as part of an ion exchange membrane reactor system. Aqueous titanium ions (Ti2+ and Ti3+) were applied to remove perchlorate ions and its destructive mechanism, reaction kinetics, and the effect of environmental factors were investigated. Titanium ions were able to degrade perchlorate ions very rapidly with half life less than one hour under conditions of high acid concentrations. A new reactor system with an ion exchange membrane was adapted to apply better the reactions of perchlorate destruction to water treatment practice. A novel treatment method was developed by integrating partially oxidized titanium ions with an ion exchange membrane, and it is named the Titanium and Membrane Hybrid System (TMH System). The results shown in this research demonstrate the feasibility of TMH System for perchlorate reduction. The perchlorate ions were rapidly adsorbed onto the ion exchange membrane and diffused through it, but they were reduced by titanium ions in the degradation zone relatively slowly. To enhance the overall rate of reaction, high concentrations of acid and Ti(III) are needed, but transport of hydrogen ions through the anion permeable membrane was observed and would be greater at higher acid concentrations. The proposed mathematical model predicts the performance and behavior of the TMH system for different physical and chemical conditions. It successfully described adsorption, diffusion and reduction of perchlorate in the system. This model could be used as an important tool for process design and optimization.

Highly oxidized species like perchlorate and nitrate that are released into the environment by anthropogenic activities are a source of concern as they have been known to contaminate groundwater. These species are extremely soluble in water and can migrate through aquifer systems, travelling substantial distances from the original site of contamination. Due to their high solubility, these oxy-anions cannot be treated using conventional treatment processes like filtration and sedimentation. Several treatment technologies are currently available to abate the human health risk due to exposure to perchlorate and nitrate. However, most of the existing treatment processes are expensive or have limitations, like generation of brines with high concentrations of perchlorate or nitrate. Aluminum can effectively reduce perchlorate and nitrate, if the protective oxide film that separates the thermodynamically reactive Al0 from most environments is removed. Aluminum was activated by pH change and electrochemically induced, pitting corrosion to remove the passivating oxide layer and expose the underlying, thermodynamically reactive, zero-valent aluminum. A partially oxidized species of aluminum, like monovalent aluminum, is believed to bring about the reduction of perchlorate and nitrate. This research studied the reduction of perchlorate and nitrate by aluminum that was activated by these two mechanisms. Results indicated that aluminum activated by pH change resulted in an instantaneous decrease in perchlorate concentration without any increase in chlorate or chloride concentrations, which suggests that the perchlorate might be adsorbed on the aluminum oxide surface. However, aluminum activated by electrochemically induced pitting corrosion can effectively reduce perchlorate to chlorate. Nitrate, on the other hand, was reduced completely to ammonia by both treatment mechanisms. The studies conducted in this dissertation suggest that aluminum can be effectively used as a reducing agent to develop a treatment process to reduce perchlorate and nitrate.

abstract: This study reports on the treatment of ammunition wastewater containing RDX (1,3,5-Trinitro-1,3,5-triazinane), HMX (1,3,5,7-Tetranitro-1,3,5,7-tetrazoctane), and the oxyanion co-contaminants nitrate (NO3-) and perchlorate (ClO4-) in a membrane biofilm reactor (MBfR), a Palladium (Pd)-coated MBfR (Pd-MBfR), and an abiotic Pd-coated film reactor (Pd-film reactor). A consortium of nitrate- and perchlorate-reducing bacteria, continuously fed with synesthetic ammunition wastewater featuring 4 mM nitrate and 0.1-2 mM perchlorate, formed robust biofilms on the membrane surfaces in the MBfR and Pd-MBfR. PdNPs with diameter 4-5-nm auto-assembled and stabilized on the surfaces of membrane and biofilm in MPfR and Pd-MBfR. Nitrate and perchlorate were rapidly reduced by the biofilms in the MBfR and Pd-MBfR, but they were not catalytically reduced through PdNPs alone in the MPfR. In contrast, RDX or HMX was recalcitrant to enzymatic degradation in MBfR, but was rapidly reduced through Pd-catalytic denitration in the MPfR and Pd-MBfR to form ‒N‒NHOH or ‒N‒H. Based on the experimental results, the synergistic coupling of Pd-based catalysis and microbial activity in the Pd-MBfR should be a viable new technology for treating ammunition wastewater. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2019

We present research investigating how, with in depth knowledge of the community, microbial communities may be harnessed for bioremediation of hazardous water contaminants. We focused on the bacterial reduction of perchlorate, a common water contaminant. For this we studied the structure and capabilities of a novel sulfur-utilizing, perchlorate-reducing bacterial (SUPeRB) consortium. Initially, we characterized the minimal consortium that retained functional capabilities, using 16S rRNA and functional gene analysis. A diverse functional consortium dominated by Beta-Proteobacteria of the family Rhodocyclaceae and sulfur-oxidizing Epsilon-Proteobacteria was found. We also examined the optimal growth conditions under which perchlorate degradation occurred and uncovered the upper limits of this function. Bacterial isolates were screened for function and the presence of functional genes. We expanded to bioreactor studies at bench- and pilot-scale, and first used a perchlorate-reducing, bench-scale bioreactor to probe the stability of the microbial ecosystem. During stable reactor function, a core consortium of Beta- and Epsilon-Proteobacteria reduced perchlorate and the co-contaminant nitrate. A disturbance of the vi consortium led to a failure in function and to higher system diversity. This suggests that the SUPeRB consortium was not metabolically flexible and high population diversity was necessary for a return to stable function. In a pilot-scale bioreactor we determined that the SUPeRB consortium could stably degrade low levels of perchlorate to below the EPA maximum recommended limit. Field conditions, such as temperature extremes and intermittent perchlorate feed, did not negatively impact overall function. When all reactor consortia were compared we observed that the volume of the reactor and the initial inoculum were not as important to stable reactor function as the acclimatization of the consortium to the system and maintenance of favorable conditions within the reactor. In summary we found that the SUPeRB consortium successfully degraded perchlorate in multiple systems. The study of this novel consortium expands our knowledge of the metabolic capabilities of perchlorate-reducing bacteria and suggests potential evolutionary pathways for perchlorate-reduction by microorganisms. The SUPeRB consortium may be used to establish bioremediation systems for perchlorate and other environmental contaminants.

Title from second page of PDF document. Includes bibliographical references (p. 144-152).

No description available.

Several electrochemical processes are modeled at process levels and atomic scales. Processes are presented for acid generation and ion exchange media regeneration, along with corresponding process models. Transport and reaction processes in individual ion exchange beads are also modeled. Acids of mild strength (pH = ~1-2) are generated from electrolyte solutions and their strength is effectively modeled as a function of time. The regeneration of ion exchange media is also modeled, to close agreement with measurements, and the process model is reconciled with a model for solute flux from an individual ion exchange bead. Together, the models show that the "gentle" regeneration process is controlled by the plating rate. Processes interior to the particle are controlled by diffusion, but all processes are faster than the characteristic time for plating. In a separate process, an electrochemical method is used to produce hypochlorite for disinfection. The process generates perchlorate as a toxic byproduct. Density function theory is used to construct an atomic-scale model of the mechanism for producing perchlorate, as well as the aging of the boron-doped diamond anode used in the process. The mechanism shows that the boron-doped diamond surface plays an important role in chemisorbing and stabilizing radicals of oxychlorine anions, allowing the radicals to live long enough to react and form higher ions like perchlorate. Wear mechanisms that occur on the anode are shown to oxidize and etch the surface, changing its chemical functionality over time. As the surface ages, the overpotential for water oxidation is decreased, decreasing the efficiency of the electrode.