Genetic engineering of Sorangium cellulosum reveals hidden enzymology in myxobacterial natural product biosynthesis

Sorangium cellulosum is a cellulolytic myxobacterium that produces a vast array of complex natural products with diverse chemical scaffolds and biological activities. However, biosynthetic investigations of these metabolites have been hindered by the scarcity of genetic manipulation tools available for their producing microorganisms. Here, we develop an efficient electroporation method for transforming foreign DNA into various Sorangium strains, enabling effective genetic engineering via homologous recombination. This facilitates delineation of the biosynthetic pathway to ambruticin, unveiling several previously undisclosed steps. Notably, AmbK is identified as the elusive epoxide hydrolase responsible for the formation of the tetrahydropyran ring during post-polyketide synthase (PKS) modification, while the terminal PKS module AmbH is shown to catalyse dual rounds of chain elongation during polyketide assembly. Our findings provide significant insights into the intricate molecular machinery governing myxobacterial natural product biosynthesis and greatly enhance our ability to further engineer Sorangium strains to unlock their biosynthetic potentials.