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Language
English (en)
Date of Award
Spring 5-2026
Author's Department
Biology
Degree Name
Bachelor of Arts (A.B.)
Restricted/Unrestricted
Restricted
Abstract
Piperazate (Piz) is a nonproteinogenic amino acid incorporated into natural products of many actinomycete bacteria. Known Piz-containing natural products exhibit antibiotic, antifungal, antiviral, antitumor, or immunosuppressive properties. The isolation of novel Piz-containing molecules is therefore a promising drug discovery strategy, particularly given the urgent need for novel bioactive scaffolds driven by the global rise of antimicrobial resistance. In this work, I applied a concordance-guided genome mining approach using pzbB, a gene encoding the enzyme responsible for L-Piz cyclization, to identify phylogenetically diverse candidate Piz-producing actinomycete strains. HPLC-MS/MS analysis of these candidates identified a previously uncharacterized strain, Streptomyces sp. SP18LM07, as a high-priority target. Subsequent genomic analysis revealed a complex hybrid NRPS-PKS Piz BGC encoding a putative novel natural product with no close precedent among characterized piperazyl compounds, and a partial chemical structure was predicted based on the metabologenomic data. In parallel, I investigated the role of ornithine availability as a limiting factor in Piz biosynthesis. Many Piz BGCs harbor additional copies of the ornithine biosynthetic genes argCJBD, and phylogenetic analysis demonstrated consistent evolutionary divergence between these BGC-associated copies and their housekeeping counterparts, suggesting a specialized biosynthetic function. However, bioinformatic analysis of the ArgJ feedback inhibition contact residues revealed complete conservation across both copy types, indicating that functional divergence, if present, does not arise through mutation of the known ornithine binding site. Together, these findings demonstrate the power of targeted, bioinformatically guided natural product discovery and advance understanding of the biosynthetic logic underlying ornithine precursor supply in Piz-producing actinomycetes.
Mentor
Joshua A.V. Blodgett
Recommended Citation
Chadwick, Bonnie E., "Discovery of Novel Piperazate-Containing Bioactive Molecules and Analysis of Underlying Biosynthetic Mechanisms" (2026). Senior Honors Papers / Undergraduate Theses. 78.
https://openscholarship.wustl.edu/undergrad_etd/78