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Biosynthetic Engineering and Molecular Regulation of Bioactive Natural Products in Lysobacter enzymogenes

Vimmy Khetrapal, University of Nebraska - Lincoln


Microbial natural products are one of the best sources for production of novel antibiotics, anticancer agents and immunosuppressants. Due to the persistent evolution of drug-resistant pathogens, the identification of novel antibiotics is extremely important. Over the past decade, Lysobacter has emerged as a rich source of bioactive natural products. This dissertation describes the regulatory mechanism and metabolic engineering of a group of natural products from Lysobacter enzymogenes for the industrial and antimicrobial applications.In the first chapter, we give a short review of structure, regulatory mechanism, and pathway engineering of HSAF and analogs, a group of polycyclic tetramate macrolactams in Lysobacter. In chapter two, we report a biosynthetic route to unsaturated odd-carbon fatty dicarboxylic acid (FDCA) based upon genetic modification of the polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) gene within L. enzymogenes. The newly engineered strain produces the C7 FDCA, hepta-2,4-dienedioic acid, an odd-carbon diunsaturated dicarboxylic acid. The subsequent chapters are based on regulatory mechanism of HSAF biosynthesis. In chapter three, we revealed a rare function of a TetR family regulator, which controls 3-hydroxylation of HSAF biosynthesis. We deleted the gene encoding a LeTetR regulator and found that the LeTetR mutant produced very little HSAF and alteramides, while the 3-dehydroxide compounds were not significantly affected. We assayed the activity of an enzyme extract from E. coli by expressing the fatty acid hydroxylase gene (hsaf-sd) and showed that the enzyme could restore the production of HSAF and alteramides in the LeTetR mutant for 3-hydroxylation of HSAF biosynthesis. In chapter four, we investigated regulatory mechanism for the LeTetR-regulated HSAF biosynthesis. We discovered that LeTetR binds to hsaf-sd gene encoding 3-hydroxylase. We have also determined that ligand binding to LeTetR affects its binding to the hsaf-sd gene which could ultimately 3-hydroxylation step of HSAF biosynthesis.

Subject Area

Biomedical engineering|Biochemistry|Molecular biology|Microbiology|Genetics

Recommended Citation

Khetrapal, Vimmy, "Biosynthetic Engineering and Molecular Regulation of Bioactive Natural Products in Lysobacter enzymogenes" (2022). ETD collection for University of Nebraska-Lincoln. AAI29168480.