Discovery and characterization of calcium-dependent antibiotics via activation of a silent natural product gene cluster
The field of natural products has enjoyed great success in identifying novel molecules from both the terrestrial and marine environments. These novel chemical discoveries have gone on to inspire pharmaceutical and biosynthetic chemists to understand the complex relationships between novel chemistry and the producing organism, the respective microbiome, and human disease. Many modern natural product success stories have started in the field or in cultivation rooms leading to novel chemistry with incredible diversity in chemical structure and bioactivity. While these traditional approaches to natural products have been invaluable to the field, the addition of genome sequencing has furthered our understanding of the chemical potential of marine microbes.
Reported herein is a brief synopsis of the history of marine natural products and its further complementation by the genetic sequencing revolution. Chapter 1 details the power of sequencing information in finding new and previously inaccessible natural products. Following this introduction, Chapter 2 describes the discovery of a “silent” biosynthetic gene cluster with similarities to the gene cluster associated with the potent antibiotic daptomycin. The isolation of this gene cluster by the novel methodology transformation-associated-recombination (TAR) cloning is then described. The activation of this gene cluster by regulator knockout is then detailed as well as the isolation and structure elucidation of the novel antibiotic taromycin A. Chapter 3 then delves further into the taromycin series with the isolation and structure elucidation of taromycin B. The unexpected rotomerization of taromycin B and the isolation and structure elucidation challenges produced as a result are discussed. Comparative bioactivity results reveal the more potent of the two novel antibiotics and these results are discussed in the historical context of daptomycin bioactivity optimization. Chapter 4 concludes this dissertation with a discussion of possible future studies with the taromycin series, TAR cloning, and genome mining as a source for novel natural products.