The role of transcription in heterologous expression of polyketides in bacterial hosts

Heterologous expression of biosynthetic pathways is an indispensable tool in the discovery, production, engineering, and characterization of bacterial polyketides and the complex enzymology involved in their biosynthesis. Ensuring transcription of polyketide biosynthetic gene clusters in heterologous hosts is a pressing problem. This review evaluates the two strategies used to ensure transcription. The first is a promoter replacement approach where promoters known to function in the heterologous host are inserted into the biosynthetic gene cluster. The second is an approach that relies on the heterologous host recognizing and utilizing promoters native to the gene cluster. Both have been successful methodologies and have different strengths and weaknesses, which are highlighted and discussed.