Date of Award
1-1-2024
Document Type
Dissertation
Degree Name
Ph.D. in Pharmaceutical Sciences
First Advisor
Paul D. Boudreau
Second Advisor
Cole Stevens
Third Advisor
Marc Slattery
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Heavy metal pollution is a significant threat to human health and the environment. Bacteria have evolved diverse mechanisms to adapt to these pollutants, including the secretion of small molecules called metallophores. Bacterial metallophores are metabolites excreted in response to toxic metal stress to protect the bacterial cell. These small molecules have shown versatility in potential applications for the remediation of heavy metals. This research focuses on constructing a library of bacterial metallophores, which will facilitate the assessment of their metal-binding properties when exposed to different metals. The study has two main areas of investigation: Firstly, it involves isolating and characterizing novel metallophores from strains in productive clades not previously characterized for siderophore production. Additionally, it involves isolating and characterizing bacteria capable of producing metallophores from heavy metal-contaminated environments. First, efforts were made to isolate new metallophores. In chapters 2 and 3, Cupriavidus necator B-4383 and Delftia lacustris DSMZ 21246 were cultured under limitation which revealed new amphiphilic metallophores structurally related to known peptidic metallophores, cupriachelin and delftibactin, respectively. The chemical structures of these metallophores were characterized based on MS/MS fragmentation, 1D-, and 2D-NMR techniques, with stereochemistry confirmed via Marfey's analysis. In the case of D. lacustris DSMZ 21246 genome mining with antiSMASH revealed the delftibactin biosynthetic gene cluster (BGC) and aided in the absolute configuration analysis. In Chapter 4, the focus shifted to isolating novel metallophore-producing bacteria from heavy metal-polluted environments. Soil samples were collected from the Carpenter Snow Creek mining district, a Superfund site in Montana. A dual-screen approach was used to select metal-tolerant strains capable of secreting metallophores. The method utilized first heavy metal-toxified plates followed by a Chrome Azurol S (CAS) assay. This work led to the isolation of eight distinct metallophore-producing bacterial species out of the soil microbiome pool, one of which, Rhodanobacter montanensis BL-MT-08, is a new bacterial species. In Chapter 5, this bacterial isolate was fully characterized through physiological, biochemical, and genomic analyses. In conclusion, this dissertation highlights the discovery of new metallophores and metallophore producers that will be investigated for the potential use in bioremediation of heavy metals.
Recommended Citation
Ahmed, Mohammed, "Bacterial Metallophores as Potential Agents in Heavy Metal Bioremediation" (2024). Electronic Theses and Dissertations. 2995.
https://egrove.olemiss.edu/etd/2995
