Establishment of the reporter system for a thylakoid-lacking cyanobacterium, Gloeobacter violaceus PCC 7421

Gloeobacter violaceus PCC 7421 is considered, by molecular phylogenetic analyses, to be an early-branching cyanobacterium within the cyanobacterial clade. G. violaceus is the only known oxygenic photosynthetic organism that lacks thylakoid membranes. There is only one report on the development of a transformation system for G. violaceus [H. Guo, X. Xu, Prog. Nat. Sci. 14 (2004) 31-35] and further studies using the system have not been reported. In the present study, we succeeded in introducing an expression vector (pKUT1121) derived from a broad-host-range plasmid, RSF1010, into G. violaceus by conjugation. The frequency of transformation of our system is significantly higher than that described in the previous report. In addition, luciferase heterologously expressed in G. violaceus functioned as a reporter. The established system will promote the molecular genetic studies on G. violaceus.