The establishment of conditions to efficiently screen photosynthesis-deficient mutants of Synechocystis sp. PCC 6803 by nitrofurantoin treatment.

A method based on the susceptibility of photosynthetic organisms to nitrofurantoin under illumination was established to screen mutants of Synechocystis sp. PCC 6803 deficient in the function of photosystem II, which were created by random PCR mutagenesis targeted to the psbAII gene coding for the D1 protein of the photosystem II reaction center. In this method, cyanobacterial colonies on a nitrocellulose membrane on a BG11 agar plate were treated with nitrofurantoin at 1.0 mM under white light at 40 microE x m(-2 ) x s(-1) for 2 h, and then kept under normal conditions without nitrofurantoin so that surviving cells could grow. This method was also shown to be useful for screening mutants deficient in the function of photosystem I.