Interplay between lipid metabolism and polyketide production in Streptomyces coelicolor

COMBA, SANTIAGO; ARABOLAZA, ANA; GRAMAJO, HUGO

Sant Feliu de Guixols

Simposio; Synthetic Biology of Antibiotic Production; 2011

European Science Foundation - European Molecular Biology Organization

Polyketides comprise one of the major families of natural bioactive products typically assembled by the condensation of several units of short-chain acyl-CoA molecules such as malonyl- and methylmalonyl-CoA. In Streptomyces, one of the most important sources of polyketides in nature, the malonyl-CoA pool is a common precursor for both, fatty acid and polyketide biosynthesis, becoming a key metabolite in the interplay between cell growth and secondary metabolism. In this sense, the flux of malonyl-CoA from primary to secondary metabolism and the availability of this molecule is a key factor that determines the yield of polyketide antibiotics production. According to this, we observed that reducing triacylglyceride (TAG) content, one of the final destinations of fatty acids in Streptomyces coelicolor, does increase the production of the polyketide actinorhodin (Act). This evidence strongly suggests that TAG biosynthesis competes with Act for the same substrates, highlighting the importance of removing this alternative carbon sink in order to increase precursor availability for polyketide synthesis. Here we describe the design and construction of S. coelicolor strains suitable for the production of malonyl-CoA based compounds. To achieve this end, we engineered S. coelicolor cells by deleting genes of competitive pathways and inserting novel enzymatic activities, to redirect the malonyl-CoA flux towards the desired product. The selected host strains were CH999 (Act-Red deficient mutant), a widely used host for in vivo production of engineered natural products; and AA0958, a mutant in TAG biosynthesis. In these genetic backgrounds, we also overexpressed the S. coelicolor acetyl-CoA Carboxylase (ACC) complex. As a straight proof of concept we have analyzed the ability of these strains to overproduce free fatty acid (a malonyl-CoA demanding product) by expressing the thioesterase TesA from Escherichia coli. The recombinant strains represent a new starting point for further chassis improvement for malonyl-CoA based compounds, such as doxorubicin, and a novel platform for systematic and combinatorial high yield production of different polyketides.