Promoter Screening Facilitates Heterologous Production of Complex Secondary Metabolites in Burkholderiales Strains.

Burkholderiales are an emerging source of bioactive secondary metabolites and have the potential to be a robust chassis for metabolites from Gram-negative bacteria. However, only a few constitutive promoters can be utilized in Burkholderiales. Herein, we described the screening of strong constitutive promoters from Burkholderiales strain DSM 7029, and 37 promoters identified from transcriptome sequencing were cloned and characterized using a firefly luciferase reporter and were further verified by qPCR analysis. These promoters were then used to drive a complex 56-kb epothilone BGC from myxobacterium and a 23-kb rhizomide BGC from Paraburkholderia rhizoxinica, and the successful production of epothilone and rhizomide was observed in DSM 7029, with improved yields compared to the production achieved by previously used promoters. Additionally, these promoters are also functional in other Burkholderiales species. Thus, these promoters are highly useful for optimizing yields of important metabolites in Burkholderiales and for mining cryptic biosynthetic pathways in DSM 7029.