A CONJUGATIVE PLASMID VECTOR FOR PROMOTER ANALYSIS IN SEVERAL CYANOBACTERIA OF THE GENERA SYNECHOCOCCUS AND SYNECHOCYSTIS

A promoter-probe vector, pSB2A, based on the plasmid RSF1010 and the p romoterless chloramphenicol acetyl transferase (cat) reporter gene, ha s been constructed. pSB2A appeared to be most efficiently transferred by conjugation to the widely used cyanobacteria Synechocystis strains PCC6803 (S.6803) and PCC6714 (S.6714) and Synechococcus strains PCC794 2 (S.7942) and PCC6301 (S.6301), where it replicates stably even thoug h it contains no cyanobacterial DNA. Using pSB2A we found that (1) a l ight-regulated promoter from S.6803 remains controlled by light intens ity in S.7942 while it is silent in Escherichia coli, and (2) the E. c oli tac promoter behaves as a strong and light-independent promoter in the four cyanobacterial hosts tested.