Date of Award
1-1-2024
Document Type
Dissertation
Degree Name
Ph.D. in Pharmaceutical Sciences
First Advisor
David C. Stevens
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Myxobacteria, first observed by Roland Thaxter in the late 19th century, are known for their unique swarming behavior, complex fruiting body formation and biosynthetic potential. Myxobacteria are noted for their large genomes and the presence of numerous biosynthetic gene clusters (BGCs) that hint at their potential to produce novel metabolites with therapeutic properties. Isolation of myxobacteria utilizing E. coli and filter paper baiting yielded 20 myxobacteria isolated from rhizospheric soil samples in North America. Among these isolates, nine were identified as novel species, representing the genera Archangium, Myxococcus, Nannocystis, Polyangium, Pyxidicoccus, Sorangium, and Stigmatella. Comprehensive growth profiles, biochemical assays, and species descriptions were conducted for these novel species. Comparative genomic analyses of these isolates, alongside previously characterized strains, revealed significant insights into their taxonomic placement and biosynthetic potential. Biosynthetic analysis using platforms like AntiSMASH and BiG-SCAPE highlighted the rich biosynthetic potential of these isolates. The findings underscore the importance of ongoing discovery and sequencing of myxobacteria from natural environments, as they enrich the genome mining pipeline with valuable BGCs. As we continued our exploration of environmental myxobacteria, we enhanced our isolation techniques and sequencing methodologies to target unique morphologies and xenic cultures within the Myxococcaceae family. Notably, we identified novel species within the genera Aggregicoccus, Vitiosangium, and Chondromyces which all have few characterized species. Despite challenges due to the unavailability of genomic data for types strains, our phylogenetic analyses revealed significant diversity among the isolates. We also optimized genome mining and DNA assembly methods to explore the biosynthetic potential of these myxobacteria. By carefully tuning the conditions for Gibson, SLIC, and CPEC assemblies, we successfully captured several representing uncharacterized pathways. The inability to isolate molecules from these pathways led to an improvement of the common vanillate promoter system. Replacing the wild type vanillate promoter with a strong andersson promoter controlled by the vanillate operator drastically improved promoter activity. Our findings underscore the genetic richness of myxobacteria and the potential for discovering novel natural products. Future work will focus on refining expression systems and exploring the biosynthetic capabilities of these intriguing microorganisms.
Recommended Citation
Ahearne, Andrew, "Isolation of Novel Myxobacteria and Progress Towards Heterologous Expression of Uncharacterized Secondary Metabolites" (2024). Electronic Theses and Dissertations. 2994.
https://egrove.olemiss.edu/etd/2994
