Heterologous activation and metabolites identification of the gene cluster from .

The microbial genome remains a huge treasure trove for the discovery of diverse natural products. NRRL23338, the industry producer of erythromycin, has a dozen of biosynthetic gene clusters whose encoding products are unidentified. Heterologous expression of one of the polyketide clusters in B4 chassis resulted in the characterization of its function responsible for synthesizing both 6-methylsalicyclic acid and 6-ethylsalicyclic acid. Meanwhile, two new 6-ethylsalicyclic acid ester derivatives were isolated as shunt metabolites. Their structures were identified by comprehensive analysis of MS and NMR experiments. Putative functions of genes within the BGC were also discussed.