A promoter-probe vector-host system for the cyanobacterium, Synechocystis PCC6803.

A vector-host system for testing promoters in the cyanobacterium Synechocystis PCC6803 has been constructed. It relies on a small Escherichia coli promoter-probe plasmid, pFF11, which has four unique restriction sites in a polylinker upstream from the cat reporter gene. This plasmid is able to obtain a cyanobacterial origin of replication by homologous recombination with the resident plasmid of the recipient host, generating a new E. coli-Synechocystis PCC6803 shuttle vector. This plasmid does not confer any detectable chloramphenicol acetyl transferase activity to this cyanobacterium in the absence of a promoter insert. Several heterologous promoters were tested in Synechocystis PCC6803 using this system. Results obtained with the lambda pR promoter and the repressor-encoding cI857 gene demonstrate that these elements can be used for high-level and tightly regulated gene expression in Synechocystis PCC6803.