Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item CHARACTERIZATION OF SEPTIC SYSTEM WASTEWATER AND MUNICIPAL SOLID WASTE LANDFILL LEACHATE(2021) Martin, Katherine; Gonsior, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The growing United States population means increasing waste production and a corresponding increase in the use and release of contaminants of emerging concern (CECs). The increasing volume and changing composition of waste poses new challenges for waste management and the protection of ecosystem, surface water, and groundwater resources. In the U.S., most domestic solid waste is disposed of in landfills, and domestic wastewater is treated by wastewater treatment plants (WWTPs) or onsite wastewater treatment systems (OWTSs). While OWTSs, the majority of which are conventional septic systems, account for the minority of wastewater treatment in the U.S., they present a significant pollution risk because they are not subject to the same treatment level or discharge regulatory standards as municipal WWTPs. Landfill leachate is also an important source of environmental contamination because most existing landfills in the U.S. are closed, unlined landfills that lack engineered systems to enhance refuse degradation or collect leachate. To mitigate the pollution risks of these effluents, it is important to understand initial wastewater composition and how to identify and trace environmental contamination.In this study, I generated background molecular composition data for landfill leachate and domestic wastewater effluents and developed chemical tracers for septic system impacted streams. I used ultrahigh resolution, Fourier-transform ion cyclotron resonance mass spectrometry, to molecularly characterize the dissolved organic matter (DOM) of septic system wastewater and septic system wastewater-impacted surface waters. I also analyzed traditional water quality markers such as CECs, chloride, nitrate isotopic signatures, and nutrients. Additionally, I molecularly characterized landfill leachate DOM and analyzed similar chemical markers to those used in the septic system study to understand composition. The goals in the main septic system study were to better understand the composition and natural processing of septic system wastewater and to develop new chemical wastewater tracers while assessing traditionally used tracers. The landfill leachate study addressed the lack of nontargeted leachate composition data. Determining initial molecular composition is necessary to understand the consequences of discharge to the environment and to design leachate treatments.Item MECHANISMS OF SORPTION OF PHARMACEUTICAL AND PERSONAL CARE PRODUCTS TO MICROPLASTICS(2021) Sanchez, Alterra; Gonsior, Michael; Yonkos, Lance; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Microplastics (MPs) are found in almost every ecosystem and in many commercially important seafood species. MPs have been found to be physically harmful to marine organisms, but also may act as vectors for organic pollutants and together have been shown to cause toxic effects in a variety of species. Wastewater effluent is a significant source of MPs to aquatic systems, as well as pharmaceutical and personal care product compounds (PPCPs). The first research contribution was to create a reference material for secondary fragment type microplastics of the polymer’s high-density polyethylene (HDPE) and polypropylene (PP) that is standardized by surface area (SA) for use in sorption and toxicity studies. Standardization for both polymers was successful, with a SA coefficient of variation of ~3%. PP MPs had greater SA due to it being a less crystalline polymer than HDPE. This reference material may act as a more realistic material than purchased powders or beads, as well as provide a more readily comparable material for fragment type MPs. The second research contribution used the reference material to create an extraction methodology for measuring semi-polar PPCPs associated with MPs. Acetone was chosen as the best solvent for extraction and extraction efficiency for both polymers was ~88% (first extraction). This methodology was then used to measure the equilibrium of the antimicrobial triclocarban with PP and PE of different MP particle sizes. Smaller particles with greater SA sorbed more triclocarban, rather than larger particles. PP had greater sorption of triclocarban than PE. This was due to PP MPs having greater SA due to being a less crystalline polymer. The third contribution created a framework for prioritizing study compounds based on environmental relevance for MP sorption using polyethylene as a model polymer, water solubility, and a correlation with the octanol water-distribution ratio, DOW, rather than the octanol-water partition coefficient, KOW. A possible threshold for polyethylene sorption was found for compounds with water solubility ~20-60mg/L and DOW ~3.7. This dissertation advances the understanding of MP reference materials, extraction methodology, sorption mechanisms, and modeling of sorption data of PPCPs.Item INVESTIGATING THE REGULATION OF GROWTH MECHANISMS IN TWO DISTINCT BRANCHES OF PHOTOSYNTHETIC LIFE(2019) Sittmann, John; Liu, Zhongchi; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Photosynthetic organisms often have limited mobility and rely on a variety of environmental, physiological, and chemical signals to regulate aspects of growth and development. In this thesis, I investigated how two such organisms, one a flowering plant and the other a heterokont alga, incorporate external signaling cues to make decisions regarding reproduction. My dissertation research is focused on 1) investigating molecular mechanisms of crosstalk between photoperiod and shade in regulating asexual reproduction in the wild strawberry Fragaria vesca, and 2) elucidating the mechanism of a bacterium-derived agent in the stimulation of cell division in the marine diatom Phaeodactylum tricornutum. First, strawberry, including woodland strawberry Fragaria vesca, is capable of a form of asexual reproduction by producing horizontal stems with daughter plants at the nodes. These horizontal stems, referred to as stolon, are derived from axillary meristems at the base of the leaves. Depending on the signals the axillary meristem receives, it will give rise to either a branch crown (a flowering shoot) or a stolon. Stolon allows for asexual reproduction to maintain the superior hybrid genotype and hence is of great significance agriculturally. Daughter plants derived from stolon are sold and propagated in strawberry farming. In this work, I have shown that a key regulatory protein FveRGA1 in GA signaling pathway functions as a repressor of stolon development. I further expanded this work by showing that the light quality (shade) signaling pathway interacts with the GA signaling to regulate stolon development. I identified and demonstrated FvePIF3 as a key transcription factor that positively regulates stolon initiation under far-red light (shade). Understanding the mechanisms underlying axillary meristem cell fate determination could advance biotechnology to increase strawberry production. Second, I have discovered and characterized a bacterium-based growth stimulation of the diatom Phaeodactylum tricornutum. Specifically, I noticed that a culture of P. tricornutum that had been accidentally contaminated with bacteria exhibited faster growth. I subsequently identified the responsible bacterium as Bacillus sp, which stimulated rapid Phaeodactylum cell division when added to the Phaeodactylum culture. I experimentally determined that the growth stimulating agent was heat labile and proteinase K-resistant. Further, I showed that the mother cell lysate of Bacillus sp. under sporulation was just as effective in promoting Phaeodactylum. In collaboration with Dr. Jon Clardy lab, we identified the growth-stimulating compounds as two distinct peptide-signaling molecules. The work revealed that the peptides may be previously under-reported signaling molecules for cross-kingdom communications. In addition to the fundamental discovery of novel signaling mechanisms between bacterium and algae, this work may facilitate large-scale diatom culture in biomass production for biofuel and biopharma.Item Characterization of Organic Compounds in Hydraulic Fracturing Fluid(2017) Luek, Jenna Lynn; Gonsior, Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Over the past decade, hydraulic fracturing combined with horizontal drilling has become the dominant technique for extracting shale gas in the US, and is increasingly important globally. A complex mixture of chemicals is used in hydraulic fracturing fluid to stimulate natural gas production, but federal regulations have exempted operators from reporting the specific chemicals used in any given well. Recent state-by-state regulations and voluntary disclosures have increased our understanding of these fluids, but knowing this list of chemicals going into a well is just the tip of the iceberg. Once these chemicals are injected, they mix with fluids and naturally occurring chemicals originating in the shale formation and can undergo physical, chemical, and biological transformations. In Chapter 2, I reviewed the literature to date regarding the characterization of organic compounds in injected hydraulic fracturing fluids and waste fluids returning to the surface. I identified a substantial knowledge gap in our understanding of organic compounds in these fluids, particularly non-volatile compounds, and potential transformations within the organic compound pool over the lifetime of the well. I analyzed a number of different shale gas wastewaters using ultrahigh resolution mass spectrometry and identified halogenated organic compounds in these fluids (Ch. 3), suggesting that these compounds were transformation products. Using a time series of shale gas fluids (Ch. 4), I was able to track changes in halogenated organic compounds and find evidence for both biological and chemical transformation pathways. Hierarchical cluster analyses helped identify sulfur-containing transformation products (Ch. 4), and I then determined that sulfur-containing molecules may be useful tracers of shale gas wastewaters in the environment (Ch. 6). In Chapter 5, I used toxicological tests and photoirradiation experiments to track the fate of organic compounds in shale gas wastewaters. Using a primarily non-targeted approach, I have been able to identify a number of organic compounds that are indicative of biological and chemical transformations occurring within hydraulic fracturing fluids and wastewaters. Understanding how these fluids change within the well and during storage and disposal provides critical information for engineering the safe and effective operation of wells, wastewater treatment techniques, and environmental impacts.Item Exploration of Lithium Ion Binding to Magnesium Bound Adenosine Triphosphate and Its Implications for Bipolar Disorder(2015) Briggs, Katharine Therese; Marino, John P.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Lithium carbonate, a drug for the treatment of Bipolar Disorder, provides mood stability to treat an illness that causes recurrent episodes of mania and/or depression. The mechanism by which lithium acts to elicit these psychological changes remains unknown. Interestingly, this small bio-active salt has been shown to reduce the risk of suicide, and appears to lower the incidence of Alzheimer’s disease. It has been proposed that lithium inhibits magnesium-dependent enzymes; however, there is no consensus as to how this occurs. Based on high resolution 7Li, 23Na, and 31P T1 and Paramagnetic Relaxation Enhancement (PRE) Nuclear Magnetic Resonance (NMR) methods, which can be used to characterize the association of lithium (Li+) at magnesium (Mg2+)-phosphorus chelation sites, we have identified a ATP•Mg•Li complex. The lithium binding affinity to form this complex is relatively high compared to other monovalent cations, with a Kd < 1 mM, and biologically relevant considering that at the typical dosing of Li+, physiological concentrations of Mg and ATP are in the 0.6 – 2.5 mM range. This has led us to propose a mechanism of action for lithium based on the formation of Mg•Li-complexes at dehydrated magnesium-phosphate sites and perhaps a role for ATP•Mg as a physiological carrier for Li+. To test this model experimentally in the context of relevant ATP-protein binding sites, we have used NMR methods to characterize the formation of the complex at ATP binding sites on albumin. Similarly, we initiated studies investigating the relevance of the ATP•Mg•Li complex to a class of purinergic receptor proteins (P2XR), since they are stimulated by purine agonists and have been implicated in Bipolar Disorder.Item Structural Variants of AI-2 Analogs to Probe Quorum Sensing in Diverse Bacteria(2011) Gamby, Sonja Josette; Sintim, Herman O.; Master of Life Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bacterial infections which were once easily managed with antibiotics are now reemerging as a serious threat to human health. The difficulty in managing infectious diseases is arising out of bacterial resistance to front line antibiotics. A new paradigm for fighting bacterial infection via the inhibition of quorum sensing has emerged. Quorum sensing is the process by which small diffusible molecules (autoinducers) are used to sense population density and upregulate genes. Notably, genes for virulence production and biofilm formation have been found to be controlled by this process. Thus, quorum sensing, offers an alternative target for the treatment of bacterial infections. One autoinducer which has been identified across many bacterial species is AI-2. The goals of this thesis were to make more hydrolytically stable analogs of AI-2 as potent inhibitors of quorum sensing, as well as, exploring the effects of AI-2 analogs on QS in P. aeruginosa. In this study, the processing of bis ester protected AI-2 analogs was examined. Also, two long chain AI-2 analogs were synthesized and tested for their ability to inhibit QS in P.aeruginosa. It was found that bis protected analogs are processed different across bacterial species. Also, long chain AI-2 analogs were found to be inhibitors of QS in P. aeruginosa, specifically, by inhibiting a LasR receptor which typically responds to a different class of autoinducer.