Synthetic Cellobiose-Inducible Regulatory Systems Allow Tight and Dynamic Controls of Gene Expression in Streptomyces.

Precise control of microbial gene expression is crucial for synthetic biotechnological applications. This is particularly true for the bacterial genus Streptomyces, major producers of diverse natural products including many antibiotics. Although a plethora of genetic tools have been developed for Streptomyces, there is still an urgent need for effective gene induction systems. We herein created two novel cellobiose-inducible regulatory systems referred to as Cel-RS1 and Cel-RS2. The regulatory systems are based upon the well-characterized repressor/operator pair CebR/cebO from Streptomyces scabies and the well-defined constitutive kasO* promoter. Both Cel-RS1 and Cel-RS2 exhibit a high level of induced reporter activity and virtually no leaky expression in three model Streptomyces species, which are commonly used as surrogate hosts for expression of natural product biosynthetic gene clusters. Cel-RS2 has been proven successful for programmable control of gene expression and controllable production of specialized metabolites in multiple Streptomyces species. The strategy can be used to expand the toolkit of inducible regulatory systems that will be broadly applicable to various Streptomyces.