Date of Award
12-1-2025
Document Type
Dissertation
Degree Name
Ph.D. in Pharmaceutical Sciences
First Advisor
Paul Boudreau
Second Advisor
Vitor Pomin
Third Advisor
Cole Stevens
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Glycosphingolipids (GSLs) are a type of membrane-lipids commonly found in eukaryotes, as well as in bacteria from the order Sphingomonadales. In these bacteria, GSLs replace lipopolysaccharides as key structural and functional components of the outer membrane. These molecules play a crucial role in maintaining membrane integrity and helping bacteria adapt to environmental stresses. Additionally, they hold significant potential in biomedical research due to their ability to modulate the immune response through interactions with the CD1d receptor. Despite their important biological and biomedical roles, the diversity and biosynthesis of bacterial GSLs are far less understood compared to their eukaryotic counterparts. In chapter 2, I conducted a thorough investigation of GSLs diversity and their structures in the Sphingomonas paucimobilis strain B-54. I analyzed the GSL profile using liquid chromatography–tandem mass spectrometry (LC-MS/MS). By interpreting the MS/MS fragmentation spectra, I was able to annotate both known and novel GSL species. In chapter 3, I studied taxonomic and genomic analyses conducted on two strains of Novosphingobium, which were isolated from a potted tomato plant in Oxford, Mississippi. These studies revealed that the strains represent two novel species: Novosphingobium oxfordense sp. nov. and Novosphingobium mississippiense sp. nov. Morphological, genomic, and chemotaxonomic analyses confirmed their distinctiveness. Furthermore, LC-MS/MS and sequence similarity network (SSN) analysis demonstrated the presence of GSLs with hexuronic acid headgroups, along with characteristic glycosyltransferase homologs involved in GSL biosynthesis. In chapter 4, I further characterized the enzymes involved in the installation of glucosamine onto glucuronic acid in the GSLs of S. paucimobilis strain B-54. Using SSN analysis, a cross-species comparison revealed seven candidate genes that might play a role in the installation of glucosamine. Functional studies, including gene knockout and heterologous approaches, along with LC-MS/MS profiling, indicated that cgt12 contributes to glucosamine installation. However, the data suggested that its activity may be partial or functionally redundant. Overall, these findings broaden the current understanding of bacterial GSL diversity and biosynthesis, providing a strong foundation for future studies on GSL-modifying enzymes and the engineering of microbial glycosphingolipids for biotechnological and therapeutic applications.
Recommended Citation
Ali, Tahir, "Mass Spectrometry- and Genomic-Based Characterization of Novel Glycosphingolipid-Producing Bacteria and Their Glycosyltransferases" (2025). Electronic Theses and Dissertations. 3500.
https://egrove.olemiss.edu/etd/3500