Selection and characterization of mutants of the cyanobacterium Synechocystis sp. PCC 6803 unable to tolerate high salt concentrations

Three mutants of the cyanobacterium Synechocystis sp. PCC 6803 unable to tolerate high salt concentrations were generated using random cartridge mutagenesis. Analysis of the phenotypes revealed that the salt sensitivity of one mutant (6803/143) is caused by a block in the synthesis of the osmoprotective substance glucosylglycerol, while in the two other mutants no physiological defect could be detected which was responsible for the loss of salt tolerance. Southern hybridization analyses and cloning of the integration sites of the resistance marker demonstrated that different genes are affected in each of the three mutants.Abbreviations aphII aminoglycoside phosphotransferase II - kb kilobasepairs - Km kanamycin - Km^r kanamycin-resistance