Theses and Dissertations - Department of Geological Sciences

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Browsing Theses and Dissertations - Department of Geological Sciences by Subject "Biochemistry"

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    Aqueous geochemistry of a sulfurous freshwater spring: implications for sulfur cycling and resident microbial communities
    (University of Alabama Libraries, 2014) Morrissey, Tacoma Nicole; Aharon, Paul; University of Alabama Tuscaloosa
    Blount Springs offers a sulfide-rich environment inhabited by a diverse microbial community in which to study the sulfur redox reactions and the microbially mediated processes via the analysis of sulfur isotopes of sulfide and sulfate. The average δ34SH2S at the wellheads is +31.1 ±0.3 / (n=9) and the average δ34SSO4 in the biofilm and downstream locations is highly variable with a mean value of +16.9 ±7.5 / (n=9). Sulfur isotope fractionations from H2S to SO4 range from 7.1 to 13.9 /. Utilizing the sulfur isotope fractionations it is concluded that (i) the sulfide is most likely derived from Thermochemical Sulfate Reduction (TSR) in the subsurface; (ii) the sulfide is subsequently oxidized to sulfate via the microbially related process of chemosynthetic sulfide oxidation; and (iii) the sulfide is also likely consumed by the abiotic processes of sulfide oxidation and outgassing of H2S. The isotopic fractionations from H2S to SO4 corroborate the isotopic fractionations observed in the laboratory during chemosynthetic sulfide oxidation. The carbon isotopic composition of DIC and the concentration of DIC support the hypothesis of microbial consumption of organic matter. Visualization of the biofilm via macroscopic and microscopic imaging revealed a morphologically diverse community. Biofilm of white, pink, and orange color were observed over the course of the study. Microscopic images revealed rod-shaped, coccoid, and filamentous cells. PCR amplification confirmed the presence of bacterial DNA. Aerobic lithotrophs, such as Thioplaca and Beggiatoa are possible groups of bacteria responsible for the chemosynthetic oxidation of sulfide at Blount Springs.
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    Biogeochemical analysis of late cretaceous vertebrate fossils of western Alabama, USA
    (University of Alabama Libraries, 2016) Harrell, Terry Lynn; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
    In the past, vertebrate paleontologists in Alabama focused primarily on classical methods of investigation, for example, by examining the gross anatomy of fossilized skeletal elements. More recently, new methods were developed that enable paleontologists to examine the molecular composition of fossilized bones and teeth, so that they may be used as proxies for determining past environmental and biological conditions. The analyses presented here examine vertebrate fossils from the Late Cretaceous aged marine formations of Alabama, which represent one of the warmest time periods in Earth’s history. The first analysis examines the rare earth element (REE) content of biophosphates to determine fossil provenance and relative paleobathymetry of the marine strata in which the fossils were deposited. The second analysis examines the strontium isotope ratios present in fossil shark tooth enameloid to determine numerical ages of the containing geologic formations. The final analysis examines the oxygen isotope content of biophosphates for ambient temperature determination of seawater present during the Late Cretaceous and the body temperatures of a variety of vertebrate organisms including mosasaurs and birds. The data obtained by this study on the greenhouse climate present during the Late Cretaceous may possibly be used to better enhance computer modelling of future climate change, given the current state of global warming, and the biological response to this warming trend.
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    High resolution molecular characterization of photochemical and microbial transformation of dissolved organic matter in temperate streams of different watershed land use
    (University of Alabama Libraries, 2014) Li, Xiaping; Lu, Yuehan; Zheng, Chunmiao; University of Alabama Tuscaloosa
    The objective of the present study was to provide better understanding of the effects of watershed land use on molecular composition of streamwater DOM and molecular transformations associated with photochemical and microbial processing of DOM. We compared DOM from headwater streams draining forest-dominated watersheds (FW) and pasture-dominated watersheds (PW) in the lower Chesapeake Bay region (Virginia, USA). Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry analysis was conducted on streamwater DOM prior to and after laboratory incubations: 1) bacteria-only incubations; 2) light-only incubations; and 3) combined light+bacterial incubations. Results showed that DOM in FW streams and PW streams differed in molecular characteristics--the former was characterized by greater structural complexity and aromaticity, higher proportions of condensed aromatic molecules and black carbon-like components, while the latter was higher in the proportions of lipid-like components, protein-like components and aliphatic compounds. Relative to DOM from FW streams, DOM from PW streams was more reactive to bacterial transformation. Protein-like components, lipid-like components and unsaturated hydrocarbon-like components are primarily responsible for the changes associated with bacterial transformation of DOM. However, similar behavior was also observed for DOM in FW streams and PW streams under the influence of bacterial and photochemical processes. Bacterial transformation reduced the proportions of lipid-like components but increased the proportions of lignin-like components and carboxyl-rich alicyclic molecule-like components, indicating that lipid-like components was a bioreactive class while lignin-like components and carboxyl-rich alicyclic were resistant to bacterial processing. Photochemical processes, alone or combined with microbial alterations, increased the proportions of protein-like components, which may be due to the light stimulation of autochthonous production of protein-like components, and increased the relative abundance of carboxyl-rich alicyclic molecule-like components, which indicates the refractory nature of these molecules. Photochemical processes also significantly reduced the amount of dissolved black carbon-like components, which suggests dissolved black carbon was a photoreactive class, countering the conventional view that black carbon was an inter group in carbon cycle. Collectively, these findings suggest that human land use in upstream watersheds may lead to alterations to the molecular composition of streamwater DOM as well as to its behavior to photochemical and microbial processing.