TitleMicrobially mediated mercury detoxification in geothermal environments
NameFreedman, Zachary (author), Barkay, Tamar (chair), Vetriani, Costatino (internal member), Haggblom, Max (internal member), Dighton, John (internal member), Reysenbach, Anna-Louise (outside member), Boyd, Eric (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectEcology and Evolution,
Geothermal resources--United States,
Yellowstone National Park--Environmental conditions
DescriptionGeothermal features are generated by leaching of minerals and metals as superheated water flows through cracks and fissures in Earth’s crust. As this water reaches the surface, chemical, pH, and temperature gradients are created that drive life in these environments. Geothermal environments are often enriched with toxic metals, e.g. mercury (Hg), the focus of this dissertation. Resistance to toxic Hg(II) is controlled by the enzyme mercuric reductase (MR), which catalyzes Hg(II) reduction to Hg(0). The gene encoding MR, merA, is part of the mercury resistance (mer) operon, which at minimum includes genes encoding transport, enzymatic, and regulatory functions. The primary objective of my research was to achieve better understanding of biotic transformations that modulate Hg toxicity in geothermal environments. I characterized Hg-resistance in Aquificae, dominant primary producers in geothermal environments, and investigated the diversity and distribution of Hg-resistance genes in geochemically diverse hot springs in Yellowstone National Park (YNP), and 23 assemblages on a global scale. Two strains of Aquificae were obtained; Hydrogenobaculum sp. Y04AAS1 (AAS1) and Hydrogenivirga sp. 128-5-R1-1 (R1-1). Genome sequencing revealed homologous sequences to merA, and alignment of putative Hg-resistance genes, MerA, MerT (Hg(II) transporter) and MerP (periplasmic scavenger), reveal homology with the mer system of Tn501. Characterization of mer in AAS1 and R1-1 include growth at Hg concentrations >10 μM Hg(II), loss of Hg(II) from the growth medium, validation of Hg(0) production, and MR enzyme activity; mer induction was not observed, suggesting lack of regulatory function. Microbial mat biomass was collected from Bijah and Succession Springs, YNP, and environmental merA sequences were obtained from GenBank to determine the ecological controls on Hg-resistant communities in YNP hot springs, and on a global scale. merA assemblages exhibited grouping within each community, and total sequence pool, as indicated by positive net relatedness index and nearest taxon index values, respectively. Cluster analyses reveal different clustering patterns of 16S rRNA and merA gene assemblages from YNP, suggesting unique controls on 16S rRNA and merA gene community structure. Meta-analysis of merA communities from 23 assemblages encompassing 782 environmental sequences reveal clustering based on sample location, suggesting that geography structures Hg-resistant communities.
NoteIncludes bibliographical references
Noteby Zachary Freedman
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.