Phage vectors that allow monitoring of transcription of secondary metabolism genes in Streptomyces.

We describe a bacteriophage phi C31-based system that permits the transcriptional fusion of the convenient reporter gene xylE to chromosomally located promoters in Streptomyces hosts. Applicability of the system to genes for secondary metabolism is demonstrated in an experiment showing that transcription of genes for actinorhodin production in Streptomyces coelicolor A3(2) depends on a transfer RNA gene (bldA) for the rare UUA codon. Two other phi C31::xylE vectors are described that allow detection of promoter activity away from their natural location, either at single copy in a prophage or during lytic infections in plaques.