Characterization of the nocardiopyrone biosynthetic gene cluster enables discovery of novel natural products

Austin Grovenstein¹, Anna Klompen¹, Rajesh Viswanathan², Amy L. Lane¹

1 Chemistry Department, University of North Florida, Jacksonville, FL
2 Department of Chemistry and Small Molecule Drug Discovery Core, Case Western Reserve University, Cleveland, OH

Nocardiopsis sp. is a marine-derived actinomycete bacterium, previously isolated off the coast of Queensland, Australia.  It synthesizes a wide range of novel compounds, many of which are biologically active.  These include the 2-pyrone-containing nocardiopyrone A.  The current study aims to reveal the biosynthetic pathway of nocardiopyrones, and elucidate the structure of several novel nocardiopyrones.  The Nocardiopsis sp. genome was sequenced, and the gene cluster hypothesized to result in nocardiopyrone production was evaluated by heterologous gene expression in a Streptomyces host.  Streptomyces clones containing this gene cluster produced nocardiopyrone A, whereas their wild-type counterparts did not.  The roles of individual genes in nocardiopyrone production were investigated by comparing nocardiopyrone yield in gene knockout mutants.  When genes encoding a polyketide synthase (PKS) enzyme were deleted, the host failed to produce nocardiopyrone.  To uncover additional compounds encoded by the nocardiopyrone gene cluster, LC-MS profiles of metabolites from the Streptomyces host expressing the nocardiopyrone gene cluster were compared with wild-type Streptomyces.  Potential novel nocardiopyrones were revealed; isolation and identification is underway.  These findings illustrate the potential of marine bacteria in synthesizing complex and useful organic molecules that may open doors for future research in synthetic chemistry and medicine.